diff --git a/addons/point_of_sale/__manifest__.py b/addons/point_of_sale/__manifest__.py
index 7e7c9a77086..7bf4d9127bd 100644
--- a/addons/point_of_sale/__manifest__.py
+++ b/addons/point_of_sale/__manifest__.py
@@ -194,7 +194,6 @@
         'point_of_sale.qunit_suite_tests': [
             'web/static/tests/legacy/component_extension_tests.js',
             'point_of_sale/static/tests/unit/**/*',
-            ('remove', 'point_of_sale/static/tests/unit/helpers/test_main.js')
         ],
         'point_of_sale.assets_backend_prod_only': [
             'point_of_sale/static/src/js/chrome_adapter.js',
diff --git a/addons/point_of_sale/static/tests/unit/helpers/test_main.js b/addons/point_of_sale/static/tests/unit/helpers/test_main.js
deleted file mode 100644
index f42e01cbd6e..00000000000
--- a/addons/point_of_sale/static/tests/unit/helpers/test_main.js
+++ /dev/null
@@ -1,23 +0,0 @@
-odoo.define('web.web_client', function (require) {
-    // this module is required by the test
-    const { bus } = require('web.core');
-    const WebClient = require('web.AbstractWebClient');
-
-    // listen to unhandled rejected promises, and when the rejection is not due
-    // to a crash, prevent the browser from displaying an 'unhandledrejection'
-    // error in the console, which would make tests crash on each Promise.reject()
-    // something similar is done by the CrashManagerService, but by default, it
-    // isn't deployed in tests
-    bus.on('crash_manager_unhandledrejection', this, function (ev) {
-        if (!ev.reason || !(ev.reason instanceof Error)) {
-            ev.stopPropagation();
-            ev.stopImmediatePropagation();
-            ev.preventDefault();
-        }
-    });
-
-    owl.config.mode = "dev";
-
-    const webClient = new WebClient();
-    return webClient;
-});
diff --git a/addons/web/__manifest__.py b/addons/web/__manifest__.py
index e596e50b492..62305f57316 100644
--- a/addons/web/__manifest__.py
+++ b/addons/web/__manifest__.py
@@ -204,7 +204,6 @@ This module provides the core of the Odoo Web Client.
 
             'web/static/src/legacy/js/services/session.js',
             'web/static/src/legacy/js/public/public_env.js',
-            'web/static/src/legacy/js/public/public_crash_manager.js',
             'web/static/src/legacy/js/public/public_root.js',
             'web/static/src/legacy/js/public/public_root_instance.js',
             'web/static/src/legacy/js/public/public_widget.js',
@@ -396,7 +395,6 @@ This module provides the core of the Odoo Web Client.
             'web/static/src/legacy/js/services/config.js',
             'web/static/src/legacy/js/services/core.js',
             'web/static/src/legacy/js/services/local_storage_service.js',
-            'web/static/src/legacy/js/services/crash_manager.js',
             'web/static/src/legacy/js/core/error_utils.js',
             'web/static/src/legacy/js/services/session_storage_service.js',
             'web/static/src/legacy/js/common_env.js',
@@ -408,7 +406,6 @@ This module provides the core of the Odoo Web Client.
 
         # Used during the transition of the web architecture
         'web.frontend_legacy': [
-            # Old rainbow man kept for website compatibility
             'web/static/src/legacy/frontend/**/*',
         ],
 
diff --git a/addons/web/static/src/core/network/rpc_service.js b/addons/web/static/src/core/network/rpc_service.js
index 0bf6056a51c..e2261754650 100644
--- a/addons/web/static/src/core/network/rpc_service.js
+++ b/addons/web/static/src/core/network/rpc_service.js
@@ -25,7 +25,7 @@ export class ConnectionAbortedError extends Error {}
 // -----------------------------------------------------------------------------
 // Main RPC method
 // -----------------------------------------------------------------------------
-function makeErrorFromResponse(reponse) {
+export function makeErrorFromResponse(reponse) {
     // Odoo returns error like this, in a error field instead of properly
     // using http error codes...
     const { code, data: errorData, message, type: subType } = reponse;
diff --git a/addons/web/static/src/legacy/frontend/public_crash_manager/public_crash_manager.js b/addons/web/static/src/legacy/frontend/public_crash_manager/public_crash_manager.js
new file mode 100644
index 00000000000..a9942498278
--- /dev/null
+++ b/addons/web/static/src/legacy/frontend/public_crash_manager/public_crash_manager.js
@@ -0,0 +1,398 @@
+odoo.define('web.CrashManager', function (require) {
+    "use strict";
+
+    const AbstractService = require('web.AbstractService');
+    var ajax = require('web.ajax');
+    var core = require('web.core');
+    var Dialog = require('web.Dialog');
+    var Widget = require('web.Widget');
+    var config = require('web.config');
+    var { formatTraceback, annotateTraceback } = require("@web/legacy/js/core/error_utils");
+
+    var _t = core._t;
+    var _lt = core._lt;
+
+    // Register this eventlistener before qunit does.
+    // Some errors needs to be negated by the crash_manager.
+    window.addEventListener('unhandledrejection', ev =>
+        core.bus.trigger('crash_manager_unhandledrejection', ev)
+    );
+
+    let active = true;
+
+    /**
+     * An extension of Dialog Widget to render the warnings and errors on the website.
+     * Extend it with your template of choice like ErrorDialog/WarningDialog
+     */
+    var CrashManagerDialog = Dialog.extend({
+        xmlDependencies: (Dialog.prototype.xmlDependencies || []).concat(
+            ['/web/static/src/legacy/frontend/public_crash_manager/public_crash_manager.xml']
+        ),
+
+        /**
+         * @param {Object} error
+         * @param {string} error.message    the message in Warning/Error Dialog
+         * @param {string} error.traceback  the traceback in ErrorDialog
+         *
+         * @constructor
+         */
+        init: function (parent, options, error) {
+            this._super.apply(this, [parent, options]);
+            this.error = error;
+            this.message = error.message;
+            this.traceback = error.traceback;
+            core.bus.off('close_dialogs', this);
+        },
+
+        willStart: async function () {
+            await this._super()
+            const jsError = this.error.data && this.error.data.jsError;
+            if (jsError) {
+                if (config.isDebug('assets')) {
+                    this.traceback = await annotateTraceback(jsError);
+                } else {
+                    this.traceback = formatTraceback(jsError);
+                }
+            }
+        },
+
+        start: async function () {
+            await this._super();
+            const message = this.message;
+            const traceback = this.traceback;
+
+            if (!traceback) {
+                return;
+            }
+            this.$(".o_error_detail").on("shown.bs.collapse", function (e) {
+                e.target.scrollTop = e.target.scrollHeight;
+            });
+
+            const $clipboardBtn = this.$(".o_clipboard_button");
+            $clipboardBtn.tooltip({title: _t("Copied !"), trigger: "manual", placement: "left"});
+            this.clipboard = new window.ClipboardJS($clipboardBtn[0], {
+                text: function () {
+                    return (_t("Error") + ":\n" + message + "\n\n" + traceback).trim();
+                },
+                // Container added because of Bootstrap modal that give the focus to another element.
+                // We need to give to correct focus to ClipboardJS (see in ClipboardJS doc)
+                // https://github.com/zenorocha/clipboard.js/issues/155
+                container: this.el,
+            });
+            this.clipboard.on("success", function (e) {
+                _.defer(function () {
+                    $clipboardBtn.tooltip("show");
+                    _.delay(function () {
+                        $clipboardBtn.tooltip("hide");
+                    }, 800);
+                });
+            });
+        },
+        destroy() {
+            if (this.clipboard) {
+                this.$(".o_clipboard_button").tooltip('dispose');
+                this.clipboard.destroy();
+            }
+            this._super();
+        }
+    });
+
+    var ErrorDialog = CrashManagerDialog.extend({
+        template: 'CrashManager.error',
+    });
+
+    var WarningDialog = CrashManagerDialog.extend({
+        template: 'CrashManager.warning',
+
+        /**
+         * Sets size to medium by default.
+         *
+         * @override
+         */
+        init: function (parent, options, error) {
+            this._super(parent, _.extend({
+                size: 'medium',
+           }, options), error);
+        },
+
+        //--------------------------------------------------------------------------
+        // Public
+        //--------------------------------------------------------------------------
+
+        /**
+         * Focuses the ok button.
+         *
+         * @override
+         */
+        open: function () {
+            this._super({shouldFocusButtons: true});
+        },
+    });
+
+    var CrashManager = AbstractService.extend({
+        init: function () {
+            var self = this;
+            active = true;
+            this.isConnected = true;
+            this.odooExceptionTitleMap = {
+                'odoo.addons.base.models.ir_mail_server.MailDeliveryException': _lt("MailDeliveryException"),
+                'odoo.exceptions.AccessDenied': _lt("Access Denied"),
+                'odoo.exceptions.AccessError': _lt("Access Error"),
+                'odoo.exceptions.MissingError': _lt("Missing Record"),
+                'odoo.exceptions.UserError': _lt("User Error"),
+                'odoo.exceptions.ValidationError': _lt("Validation Error"),
+                'odoo.exceptions.Warning': _lt("Warning"),
+            };
+
+            this._super.apply(this, arguments);
+
+            // crash manager integration
+            core.bus.on('rpc_error', this, this.rpc_error);
+            window.onerror = function (message, file, line, col, error) {
+                // Scripts injected in DOM (eg: google API's js files) won't return a clean error on window.onerror.
+                // The browser will just give you a 'Script error.' as message and nothing else for security issue.
+                // To enable onerror to work properly with CORS file, you should:
+                //   1. add crossorigin="anonymous" to your <script> tag loading the file
+                //   2. enabling 'Access-Control-Allow-Origin' on the server serving the file.
+                // Since in some case it wont be possible to to this, this handle should have the possibility to be
+                // handled by the script manipulating the injected file. For this, you will use window.onOriginError
+                // If it is not handled, we should display something clearer than the common crash_manager error dialog
+                // since it won't show anything except "Script error."
+                // This link will probably explain it better: https://blog.sentry.io/2016/05/17/what-is-script-error.html
+                if (!file && !line && !col) {
+                    // Chrome and Opera set "Script error." on the `message` and hide the `error`
+                    // Firefox handles the "Script error." directly. It sets the error thrown by the CORS file into `error`
+                    if (window.onOriginError) {
+                        window.onOriginError();
+                        delete window.onOriginError;
+                    } else {
+                        self.show_error({
+                            type: _t("Odoo Client Error"),
+                            message: _t("Unknown CORS error"),
+                            data: {debug: _t("An unknown CORS error occured. The error probably originates from a JavaScript file served from a different origin. (Opening your browser console might give you a hint on the error.)")},
+                        });
+                    }
+                } else {
+                    // ignore Chrome video internal error: https://crbug.com/809574
+                    if (!error && message === 'ResizeObserver loop limit exceeded') {
+                        return;
+                    }
+                    var traceback = error ? error.stack : '';
+                    self.show_error({
+                        type: _t("Odoo Client Error"),
+                        message: message,
+                        data: {debug: file + ':' + line + "\n" + _t('Traceback:') + "\n" + traceback, jsError: error},
+                    });
+                }
+            };
+
+            // listen to unhandled rejected promises, and throw an error when the
+            // promise has been rejected due to a crash
+            core.bus.on('crash_manager_unhandledrejection', this, function (ev) {
+                if (ev.reason && ev.reason instanceof Error) {
+                    let traceback = ev.reason.stack;
+                    self.show_error({
+                        type: _t("Odoo Client Error"),
+                        message: '',
+                        data: {debug: _t('Traceback:') + "\n" + traceback, jsError: ev.reason},
+                    });
+                } else {
+                    // the rejection is not due to an Error, so prevent the browser
+                    // from displaying an 'unhandledrejection' error in the console
+                    ev.stopPropagation();
+                    ev.stopImmediatePropagation();
+                    ev.preventDefault();
+                }
+            });
+        },
+        enable: function () {
+            active = true;
+        },
+        disable: function () {
+            active = false;
+        },
+        handleLostConnection: function () {
+            var self = this;
+            if (!this.isConnected) {
+                // already handled, nothing to do.  This can happen when several
+                // rpcs are done in parallel and fail because of a lost connection.
+                return;
+            }
+            this.isConnected = false;
+            var delay = 2000;
+            core.bus.trigger('connection_lost');
+
+            setTimeout(function checkConnection() {
+                ajax.jsonRpc('/web/webclient/version_info', 'call', {}, {shadow:true}).then(function () {
+                    core.bus.trigger('connection_restored');
+                    self.isConnected = true;
+                }).guardedCatch(function () {
+                    // exponential backoff, with some jitter
+                    delay = (delay * 1.5) + 500*Math.random();
+                    setTimeout(checkConnection, delay);
+                });
+            }, delay);
+        },
+        rpc_error: function(error) {
+            // Some qunit tests produces errors before the DOM is set.
+            // This produces an error loop as the modal/toast has no DOM to attach to.
+            if (!document.body || !active || this.connection_lost) return;
+
+            // Connection lost error
+            if (error.code === -32098) {
+                this.handleLostConnection();
+                return;
+            }
+
+            // Special exception handlers, see crash_registry bellow
+            var handler = core.crash_registry.get(error.data.name, true);
+            if (handler) {
+                new (handler)(this, error).display();
+                return;
+            }
+
+            // Odoo custom exception: UserError, AccessError, ...
+            if (_.has(this.odooExceptionTitleMap, error.data.name)) {
+                error = _.extend({}, error, {
+                    data: _.extend({}, error.data, {
+                        message: error.data.arguments[0],
+                        title: this.odooExceptionTitleMap[error.data.name],
+                    }),
+                });
+                this.show_warning(error);
+                return;
+            }
+
+            // Any other Python exception
+            this.show_error(error);
+        },
+        show_warning: function (error, options) {
+            if (!active) {
+                return;
+            }
+            var message = error.data ? error.data.message : error.message;
+            var title = _t("Something went wrong !");
+            if (error.type) {
+                title = _.str.capitalize(error.type);
+            } else if (error.data && error.data.title) {
+                title = _.str.capitalize(error.data.title);
+            }
+
+            return this.displayNotification(Object.assign({}, options, {
+                title,
+                message,
+                sticky: true,
+            }));
+        },
+        show_error: function (error) {
+            if (!active) {
+                return;
+            }
+            error.traceback = error.data.debug;
+            var dialog = new ErrorDialog(this, {
+                title: _.str.capitalize(error.type) || _t("Odoo Error"),
+            }, error);
+
+            return dialog.open();
+        },
+        show_message: function(exception) {
+            return this.show_error({
+                type: _t("Odoo Client Error"),
+                message: exception,
+                data: {debug: ""}
+            });
+        },
+    });
+
+    /**
+     * An interface to implement to handle exceptions. Register implementation in instance.web.crash_manager_registry.
+    */
+    var ExceptionHandler = {
+        /**
+         * @param parent The parent.
+         * @param error The error object as returned by the JSON-RPC implementation.
+         */
+        init: function(parent, error) {},
+        /**
+         * Called to inform to display the widget, if necessary. A typical way would be to implement
+         * this interface in a class extending instance.web.Dialog and simply display the dialog in this
+         * method.
+         */
+        display: function() {},
+    };
+
+
+    /**
+     * Handle redirection warnings, which behave more or less like a regular
+     * warning, with an additional redirection button.
+     */
+    var RedirectWarningHandler = Widget.extend(ExceptionHandler, {
+        init: function(parent, error) {
+            this._super(parent);
+            this.error = error;
+        },
+        display: function() {
+            var self = this;
+            var error = this.error;
+            var additional_context = _.extend({}, this.context, error.data.arguments[3]);
+
+            new WarningDialog(this, {
+                title: _.str.capitalize(error.type) || _t("Odoo Warning"),
+                buttons: [
+                    {text: error.data.arguments[2], classes : "btn-primary", click: function() {
+                        self.do_action(
+                            error.data.arguments[1],
+                            {
+                                additional_context: additional_context,
+                            });
+                            self.destroy();
+                    }, close: true},
+                    {text: _t("Cancel"), click: function() { self.destroy(); }, close: true}
+                ]
+            }, {
+                message: error.data.arguments[0],
+            }).open();
+        }
+    });
+
+    core.crash_registry.add('odoo.exceptions.RedirectWarning', RedirectWarningHandler);
+
+    function session_expired(cm) {
+        return {
+            display: function () {
+                const notif = {
+                    type: _t("Odoo Session Expired"),
+                    message: _t("Your Odoo session expired. The current page is about to be refreshed."),
+                };
+                const options = {
+                    buttons: [{
+                        text: _t("Ok"),
+                        click: () => window.location.reload(true),
+                        close: true
+                    }],
+                };
+                cm.show_warning(notif, options);
+            }
+        };
+    }
+    core.crash_registry.add('odoo.http.SessionExpiredException', session_expired);
+    core.crash_registry.add('werkzeug.exceptions.Forbidden', session_expired);
+
+    core.crash_registry.add('504', function (cm) {
+        return {
+            display: function () {
+                cm.show_warning({
+                    type: _t("Request timeout"),
+                    message: _t("The operation was interrupted. This usually means that the current operation is taking too much time.")});
+            }
+        };
+    });
+    core.serviceRegistry.add('crash_manager', CrashManager);
+
+    return {
+        CrashManager: CrashManager,
+        ErrorDialog: ErrorDialog,
+        WarningDialog: WarningDialog,
+        disable: () => active = false,
+    };
+});
diff --git a/addons/web/static/src/legacy/xml/crash_manager.xml b/addons/web/static/src/legacy/frontend/public_crash_manager/public_crash_manager.xml
similarity index 100%
rename from addons/web/static/src/legacy/xml/crash_manager.xml
rename to addons/web/static/src/legacy/frontend/public_crash_manager/public_crash_manager.xml
diff --git a/addons/web/static/src/legacy/js/_deprecated/crash_manager_warning_dialog.js b/addons/web/static/src/legacy/js/_deprecated/crash_manager_warning_dialog.js
new file mode 100644
index 00000000000..9697257d59f
--- /dev/null
+++ b/addons/web/static/src/legacy/js/_deprecated/crash_manager_warning_dialog.js
@@ -0,0 +1,30 @@
+/** @odoo-module */
+import Dialog from "web.Dialog";
+import core from "web.core";
+
+/**
+ * An extension of Dialog Widget to render warnings.
+ */
+export const WarningDialog = Dialog.extend({
+    template: 'web.LegacyWarningDialog',
+    /**
+     * @param {Object} error
+     * @param {string} error.message    the message in Warning Dialog
+     *
+     * @constructor
+     */
+    init: function (parent, options, error) {
+        options.size = options.size || "medium";
+        this._super.apply(this, [parent, options]);
+        this.message = error.message;
+        core.bus.off('close_dialogs', this);
+    },
+    /**
+     * Focuses the ok button.
+     *
+     * @override
+     */
+    open: function () {
+        this._super({shouldFocusButtons: true});
+    },
+});
diff --git a/addons/web/static/src/legacy/js/core/misc.js b/addons/web/static/src/legacy/js/core/misc.js
index 11ee7c46d3e..6b736b6edca 100644
--- a/addons/web/static/src/legacy/js/core/misc.js
+++ b/addons/web/static/src/legacy/js/core/misc.js
@@ -4,7 +4,6 @@ odoo.define('web.framework', function (require) {
 var core = require('web.core');
 var ajax = require('web.ajax');
 var Widget = require('web.Widget');
-var disableCrashManager = require('web.CrashManager').disable;
 const {sprintf} = require('web.utils')
 
 var _t = core._t;
@@ -101,9 +100,6 @@ function unblockUI() {
  * If wait is true, sleep 1s and wait for the server i.e. after a restart.
  */
 function redirect (url, wait) {
-    // Dont display a dialog if some xmlhttprequest are in progress
-    disableCrashManager();
-
     var load = function() {
         var old = "" + window.location;
         var old_no_hash = old.split("#")[0];
diff --git a/addons/web/static/src/legacy/js/fields/basic_fields.js b/addons/web/static/src/legacy/js/fields/basic_fields.js
index 1138f6c917b..16e433da52b 100644
--- a/addons/web/static/src/legacy/js/fields/basic_fields.js
+++ b/addons/web/static/src/legacy/js/fields/basic_fields.js
@@ -1898,7 +1898,6 @@ var AbstractFieldBinary = AbstractField.extend({
     on_file_uploaded: function (size, name) {
         if (size === false) {
             this.displayNotification({ message: _t("There was a problem while uploading your file"), type: 'danger' });
-            // TODO: use crashmanager
             console.warn("Error while uploading file : ", name);
         } else {
             this.on_file_uploaded_and_valid.apply(this, arguments);
diff --git a/addons/web/static/src/legacy/js/public/public_crash_manager.js b/addons/web/static/src/legacy/js/public/public_crash_manager.js
deleted file mode 100644
index 8eae270f23a..00000000000
--- a/addons/web/static/src/legacy/js/public/public_crash_manager.js
+++ /dev/null
@@ -1,31 +0,0 @@
-odoo.define('web.PublicCrashManager', function (require) {
-"use strict";
-
-const core = require('web.core');
-const CrashManager = require('web.CrashManager').CrashManager;
-
-const PublicCrashManager = CrashManager.extend({
-
-    //--------------------------------------------------------------------------
-    // Private
-    //--------------------------------------------------------------------------
-
-    /**
-     * @override
-     */
-    _displayWarning(message, title, options) {
-        this.displayNotification(Object.assign({}, options, {
-            title,
-            message,
-            sticky: true,
-        }));
-    },
-});
-
-core.serviceRegistry.add('crash_manager', PublicCrashManager);
-
-return {
-    CrashManager: PublicCrashManager,
-};
-
-});
diff --git a/addons/web/static/src/legacy/js/services/crash_manager.js b/addons/web/static/src/legacy/js/services/crash_manager.js
deleted file mode 100644
index 0bac7cfe78d..00000000000
--- a/addons/web/static/src/legacy/js/services/crash_manager.js
+++ /dev/null
@@ -1,421 +0,0 @@
-odoo.define('web.ErrorDialogRegistry', function (require) {
-"use strict";
-
-var Registry = require('web.Registry');
-
-return new Registry();
-});
-
-odoo.define('web.CrashManager', function (require) {
-"use strict";
-
-const AbstractService = require('web.AbstractService');
-var ajax = require('web.ajax');
-const BrowserDetection = require('web.BrowserDetection');
-var core = require('web.core');
-var Dialog = require('web.Dialog');
-var ErrorDialogRegistry = require('web.ErrorDialogRegistry');
-var Widget = require('web.Widget');
-var config = require('web.config');
-var { formatTraceback, annotateTraceback} = require("@web/legacy/js/core/error_utils");
-
-var _t = core._t;
-var _lt = core._lt;
-
-// Register this eventlistener before qunit does.
-// Some errors needs to be negated by the crash_manager.
-window.addEventListener('unhandledrejection', ev =>
-    core.bus.trigger('crash_manager_unhandledrejection', ev)
-);
-
-let active = true;
-
-/**
- * An extension of Dialog Widget to render the warnings and errors on the website.
- * Extend it with your template of choice like ErrorDialog/WarningDialog
- */
-var CrashManagerDialog = Dialog.extend({
-    xmlDependencies: (Dialog.prototype.xmlDependencies || []).concat(
-        ['/web/static/src/legacy/xml/crash_manager.xml']
-    ),
-
-    /**
-     * @param {Object} error
-     * @param {string} error.message    the message in Warning/Error Dialog
-     * @param {string} error.traceback  the traceback in ErrorDialog
-     *
-     * @constructor
-     */
-    init: function (parent, options, error) {
-        this._super.apply(this, [parent, options]);
-        this.error = error;
-        this.message = error.message;
-        this.traceback = error.traceback;
-        core.bus.off('close_dialogs', this);
-    },
-
-    willStart: async function () {
-        await this._super()
-        const jsError = this.error.data && this.error.data.jsError;
-        if (jsError) {
-            if (config.isDebug('assets')) {
-                this.traceback = await annotateTraceback(jsError);
-            } else {
-                this.traceback = formatTraceback(jsError);
-            }
-        }
-    },
-
-    start: async function () {
-        await this._super();
-        const message = this.message;
-        const traceback = this.traceback;
-
-        if (!traceback) {
-            return;
-        }
-        this.$(".o_error_detail").on("shown.bs.collapse", function (e) {
-            e.target.scrollTop = e.target.scrollHeight;
-        });
-
-        const $clipboardBtn = this.$(".o_clipboard_button");
-        $clipboardBtn.tooltip({title: _t("Copied !"), trigger: "manual", placement: "left"});
-        this.clipboard = new window.ClipboardJS($clipboardBtn[0], {
-            text: function () {
-                return (_t("Error") + ":\n" + message + "\n\n" + traceback).trim();
-            },
-            // Container added because of Bootstrap modal that give the focus to another element.
-            // We need to give to correct focus to ClipboardJS (see in ClipboardJS doc)
-            // https://github.com/zenorocha/clipboard.js/issues/155
-            container: this.el,
-        });
-        this.clipboard.on("success", function (e) {
-            _.defer(function () {
-                $clipboardBtn.tooltip("show");
-                _.delay(function () {
-                    $clipboardBtn.tooltip("hide");
-                }, 800);
-            });
-        });
-    },
-    destroy() {
-        if (this.clipboard) {
-            this.$(".o_clipboard_button").tooltip('dispose');
-            this.clipboard.destroy();
-        }
-        this._super();
-    }
-});
-
-var ErrorDialog = CrashManagerDialog.extend({
-    template: 'CrashManager.error',
-});
-
-var WarningDialog = CrashManagerDialog.extend({
-    template: 'CrashManager.warning',
-
-    /**
-     * Sets size to medium by default.
-     *
-     * @override
-     */
-    init: function (parent, options, error) {
-        this._super(parent, _.extend({
-            size: 'medium',
-       }, options), error);
-    },
-
-    //--------------------------------------------------------------------------
-    // Public
-    //--------------------------------------------------------------------------
-
-    /**
-     * Focuses the ok button.
-     *
-     * @override
-     */
-    open: function () {
-        this._super({shouldFocusButtons: true});
-    },
-});
-
-var CrashManager = AbstractService.extend({
-    init: function () {
-        var self = this;
-        active = true;
-        this.isConnected = true;
-        this.odooExceptionTitleMap = {
-            'odoo.addons.base.models.ir_mail_server.MailDeliveryException': _lt("MailDeliveryException"),
-            'odoo.exceptions.AccessDenied': _lt("Access Denied"),
-            'odoo.exceptions.AccessError': _lt("Access Error"),
-            'odoo.exceptions.MissingError': _lt("Missing Record"),
-            'odoo.exceptions.UserError': _lt("User Error"),
-            'odoo.exceptions.ValidationError': _lt("Validation Error"),
-            'odoo.exceptions.Warning': _lt("Warning"),
-        };
-
-        this._super.apply(this, arguments);
-
-        // crash manager integration
-        core.bus.on('rpc_error', this, this.rpc_error);
-        window.onerror = function (message, file, line, col, error) {
-            // Scripts injected in DOM (eg: google API's js files) won't return a clean error on window.onerror.
-            // The browser will just give you a 'Script error.' as message and nothing else for security issue.
-            // To enable onerror to work properly with CORS file, you should:
-            //   1. add crossorigin="anonymous" to your <script> tag loading the file
-            //   2. enabling 'Access-Control-Allow-Origin' on the server serving the file.
-            // Since in some case it wont be possible to to this, this handle should have the possibility to be
-            // handled by the script manipulating the injected file. For this, you will use window.onOriginError
-            // If it is not handled, we should display something clearer than the common crash_manager error dialog
-            // since it won't show anything except "Script error."
-            // This link will probably explain it better: https://blog.sentry.io/2016/05/17/what-is-script-error.html
-            if (!file && !line && !col) {
-                // Chrome and Opera set "Script error." on the `message` and hide the `error`
-                // Firefox handles the "Script error." directly. It sets the error thrown by the CORS file into `error`
-                if (window.onOriginError) {
-                    window.onOriginError();
-                    delete window.onOriginError;
-                } else {
-                    self.show_error({
-                        type: _t("Odoo Client Error"),
-                        message: _t("Unknown CORS error"),
-                        data: {debug: _t("An unknown CORS error occured. The error probably originates from a JavaScript file served from a different origin. (Opening your browser console might give you a hint on the error.)")},
-                    });
-                }
-            } else {
-                // ignore Chrome video internal error: https://crbug.com/809574
-                if (!error && message === 'ResizeObserver loop limit exceeded') {
-                    return;
-                }
-                var traceback = error ? error.stack : '';
-                self.show_error({
-                    type: _t("Odoo Client Error"),
-                    message: message,
-                    data: {debug: file + ':' + line + "\n" + _t('Traceback:') + "\n" + traceback, jsError: error},
-                });
-            }
-        };
-
-        // listen to unhandled rejected promises, and throw an error when the
-        // promise has been rejected due to a crash
-        core.bus.on('crash_manager_unhandledrejection', this, function (ev) {
-            if (ev.reason && ev.reason instanceof Error) {
-                let traceback = ev.reason.stack;
-                self.show_error({
-                    type: _t("Odoo Client Error"),
-                    message: '',
-                    data: {debug: _t('Traceback:') + "\n" + traceback, jsError: ev.reason},
-                });
-            } else {
-                // the rejection is not due to an Error, so prevent the browser
-                // from displaying an 'unhandledrejection' error in the console
-                ev.stopPropagation();
-                ev.stopImmediatePropagation();
-                ev.preventDefault();
-            }
-        });
-    },
-    enable: function () {
-        active = true;
-    },
-    disable: function () {
-        active = false;
-    },
-    handleLostConnection: function () {
-        var self = this;
-        if (!this.isConnected) {
-            // already handled, nothing to do.  This can happen when several
-            // rpcs are done in parallel and fail because of a lost connection.
-            return;
-        }
-        this.isConnected = false;
-        var delay = 2000;
-        core.bus.trigger('connection_lost');
-
-        setTimeout(function checkConnection() {
-            ajax.jsonRpc('/web/webclient/version_info', 'call', {}, {shadow:true}).then(function () {
-                core.bus.trigger('connection_restored');
-                self.isConnected = true;
-            }).guardedCatch(function () {
-                // exponential backoff, with some jitter
-                delay = (delay * 1.5) + 500*Math.random();
-                setTimeout(checkConnection, delay);
-            });
-        }, delay);
-    },
-    rpc_error: function(error) {
-        // Some qunit tests produces errors before the DOM is set.
-        // This produces an error loop as the modal/toast has no DOM to attach to.
-        if (!document.body || !active || this.connection_lost) return;
-
-        // Connection lost error
-        if (error.code === -32098) {
-            this.handleLostConnection();
-            return;
-        }
-
-        // Special exception handlers, see crash_registry bellow
-        var handler = core.crash_registry.get(error.data.name, true);
-        if (handler) {
-            new (handler)(this, error).display();
-            return;
-        }
-
-        // Odoo custom exception: UserError, AccessError, ...
-        if (_.has(this.odooExceptionTitleMap, error.data.name)) {
-            error = _.extend({}, error, {
-                data: _.extend({}, error.data, {
-                    message: error.data.arguments[0],
-                    title: this.odooExceptionTitleMap[error.data.name],
-                }),
-            });
-            this.show_warning(error);
-            return;
-        }
-
-        // Any other Python exception
-        this.show_error(error);
-    },
-    show_warning: function (error, options) {
-        if (!active) {
-            return;
-        }
-        var message = error.data ? error.data.message : error.message;
-        var title = _t("Something went wrong !");
-        if (error.type) {
-            title = _.str.capitalize(error.type);
-        } else if (error.data && error.data.title) {
-            title = _.str.capitalize(error.data.title);
-        }
-        return this._displayWarning(message, title, options);
-    },
-    show_error: function (error) {
-        if (!active) {
-            return;
-        }
-        error.traceback = error.data.debug;
-        var dialogClass = error.data.context && ErrorDialogRegistry.get(error.data.context.exception_class) || ErrorDialog;
-        var dialog = new dialogClass(this, {
-            title: _.str.capitalize(error.type) || _t("Odoo Error"),
-        }, error);
-
-        return dialog.open();
-    },
-    show_message: function(exception) {
-        return this.show_error({
-            type: _t("Odoo Client Error"),
-            message: exception,
-            data: {debug: ""}
-        });
-    },
-
-    //--------------------------------------------------------------------------
-    // Private
-    //--------------------------------------------------------------------------
-
-    /**
-     * @private
-     * @param {string} message
-     * @param {string} title
-     * @param {Object} options
-     */
-    _displayWarning: function (message, title, options) {
-        return new WarningDialog(this, Object.assign({}, options, {
-            title,
-        }), {
-            message,
-        }).open();
-    },
-});
-
-/**
- * An interface to implement to handle exceptions. Register implementation in instance.web.crash_manager_registry.
-*/
-var ExceptionHandler = {
-    /**
-     * @param parent The parent.
-     * @param error The error object as returned by the JSON-RPC implementation.
-     */
-    init: function(parent, error) {},
-    /**
-     * Called to inform to display the widget, if necessary. A typical way would be to implement
-     * this interface in a class extending instance.web.Dialog and simply display the dialog in this
-     * method.
-     */
-    display: function() {},
-};
-
-
-/**
- * Handle redirection warnings, which behave more or less like a regular
- * warning, with an additional redirection button.
- */
-var RedirectWarningHandler = Widget.extend(ExceptionHandler, {
-    init: function(parent, error) {
-        this._super(parent);
-        this.error = error;
-    },
-    display: function() {
-        var self = this;
-        var error = this.error;
-        var additional_context = _.extend({}, this.context, error.data.arguments[3]);
-
-        new WarningDialog(this, {
-            title: _.str.capitalize(error.type) || _t("Odoo Warning"),
-            buttons: [
-                {text: error.data.arguments[2], classes : "btn-primary", click: function() {
-                    self.do_action(
-                        error.data.arguments[1],
-                        {
-                            additional_context: additional_context,
-                        });
-                        self.destroy();
-                }, close: true},
-                {text: _t("Cancel"), click: function() { self.destroy(); }, close: true}
-            ]
-        }, {
-            message: error.data.arguments[0],
-        }).open();
-    }
-});
-
-core.crash_registry.add('odoo.exceptions.RedirectWarning', RedirectWarningHandler);
-
-function session_expired(cm) {
-    return {
-        display: function () {
-            const notif = {
-                type: _t("Odoo Session Expired"),
-                message: _t("Your Odoo session expired. The current page is about to be refreshed."),
-            };
-            const options = {
-                buttons: [{
-                    text: _t("Ok"),
-                    click: () => window.location.reload(true),
-                    close: true
-                }],
-            };
-            cm.show_warning(notif, options);
-        }
-    };
-}
-core.crash_registry.add('odoo.http.SessionExpiredException', session_expired);
-core.crash_registry.add('werkzeug.exceptions.Forbidden', session_expired);
-
-core.crash_registry.add('504', function (cm) {
-    return {
-        display: function () {
-            cm.show_warning({
-                type: _t("Request timeout"),
-                message: _t("The operation was interrupted. This usually means that the current operation is taking too much time.")});
-        }
-    };
-});
-
-return {
-    CrashManager: CrashManager,
-    ErrorDialog: ErrorDialog,
-    WarningDialog: WarningDialog,
-    disable: () => active = false,
-};
-});
diff --git a/addons/web/static/src/legacy/legacy_setup.js b/addons/web/static/src/legacy/legacy_setup.js
index 2e74f5d48cc..e0f3c7de58f 100644
--- a/addons/web/static/src/legacy/legacy_setup.js
+++ b/addons/web/static/src/legacy/legacy_setup.js
@@ -7,6 +7,7 @@ import {
     makeLegacyRpcService,
     makeLegacySessionService,
     makeLegacyDialogMappingService,
+    makeLegacyCrashManagerService,
 } from "./utils";
 import * as AbstractService from "web.AbstractService";
 import * as legacyEnv from "web.env";
@@ -38,8 +39,9 @@ export const legacySetupProm = new Promise((resolve) => {
     serviceRegistry.add("legacy_session", legacySessionService);
     const legacyWebClientService = makeLegacyWebClientService(legacyEnv);
     serviceRegistry.add("legacy_web_client", legacyWebClientService);
-    const legacyDialogMappingService = makeLegacyDialogMappingService(legacyEnv);
     serviceRegistry.add("legacy_notification", makeLegacyNotificationService(legacyEnv));
+    serviceRegistry.add("legacy_crash_manager", makeLegacyCrashManagerService(legacyEnv));
+    const legacyDialogMappingService = makeLegacyDialogMappingService(legacyEnv);
     serviceRegistry.add("legacy_dialog_mapping", legacyDialogMappingService);
     await Promise.all([whenReady(), session.is_bound]);
     legacyEnv.qweb.addTemplates(session.owlTemplates);
diff --git a/addons/web/static/src/legacy/utils.js b/addons/web/static/src/legacy/utils.js
index d752124e050..672f006474d 100644
--- a/addons/web/static/src/legacy/utils.js
+++ b/addons/web/static/src/legacy/utils.js
@@ -2,7 +2,12 @@
 
 import { browser } from "../core/browser/browser";
 import AbstractStorageService from "web.AbstractStorageService";
-import { ConnectionAbortedError, RPCError } from "../core/network/rpc_service";
+import {
+    ConnectionAbortedError,
+    RPCError,
+    makeErrorFromResponse,
+} from "../core/network/rpc_service";
+import { ErrorDialog } from "../core/errors/error_dialogs";
 
 export function mapDoActionOptionAPI(legacyOptions) {
     legacyOptions = legacyOptions || {};
@@ -257,3 +262,20 @@ export function makeLegacyNotificationService(legacyEnv) {
         },
     };
 }
+
+export function makeLegacyCrashManagerService(legacyEnv) {
+    return {
+        dependencies: ["dialog"],
+        start(env) {
+            legacyEnv.services.crash_manager = {
+                show_message(message) {
+                    env.services.dialog.open(ErrorDialog, { traceback: message });
+                },
+                rpc_error(errorResponse) {
+                    // Will be handled by error_service
+                    Promise.reject(makeErrorFromResponse(errorResponse));
+                },
+            };
+        },
+    };
+}
diff --git a/addons/web/static/src/legacy/xml/dialog.xml b/addons/web/static/src/legacy/xml/dialog.xml
index 848f5a1e9b6..790f8251a6b 100644
--- a/addons/web/static/src/legacy/xml/dialog.xml
+++ b/addons/web/static/src/legacy/xml/dialog.xml
@@ -23,5 +23,8 @@
         </div>
     </div>
 </t>
+<div t-name="web.LegacyWarningDialog" class="o_dialog_warning" role="alert">
+    <p t-esc="widget.message" style="white-space: pre-wrap;"/>
+</div>
 
 </templates>
diff --git a/addons/web/static/tests/helpers/legacy.js b/addons/web/static/tests/helpers/legacy.js
index 48ee63f7b47..931f2b67ebd 100644
--- a/addons/web/static/tests/helpers/legacy.js
+++ b/addons/web/static/tests/helpers/legacy.js
@@ -26,8 +26,6 @@ odoo.define("web.test_legacy", async (require) => {
         const session = require("web.session");
         await session.is_bound; // await for templates from server
         require("web.test_utils");
-        const LegacyCrashManager = require("web.CrashManager");
-        LegacyCrashManager.disable();
         resolve();
     });
 
diff --git a/addons/web/static/tests/legacy/helpers/test_utils.js b/addons/web/static/tests/legacy/helpers/test_utils.js
index f96d2203c1f..06837d007ef 100644
--- a/addons/web/static/tests/legacy/helpers/test_utils.js
+++ b/addons/web/static/tests/legacy/helpers/test_utils.js
@@ -123,7 +123,6 @@ odoo.define('web.test_utils', async function (require) {
     // to load xml files that are normally lazy loaded by specific widgets).
     await Promise.all([
         session.is_bound,
-        ajax.loadXML('/web/static/src/legacy/xml/crash_manager.xml', core.qweb),
         ajax.loadXML('/web/static/src/legacy/frontend/debug_manager/debug.xml', core.qweb),
         ajax.loadXML('/web/static/src/legacy/xml/dialog.xml', core.qweb),
         ajax.loadXML('/web/static/src/legacy/xml/translation_dialog.xml', core.qweb),