---
title: "Breaking: #96575 - Update to CodeMirror 6"
manual: "TYPO3 Core Changelog"
version: "main"
permalink: "https://docs.typo3.org/permalink/changelog:breaking-96575-1663324432"
source: "Changelog/12.0/Breaking-96575-UpdateToCodeMirror6.rst"
typo3-version: "12.0"
typo3-major: 12
type: "breaking"
issue: 96575
forge: "https://forge.typo3.org/issues/96575"
tags: ["Backend", "JavaScript", "NotScanned", "ext:t3editor"]
rendered: "2026-09-24T21:45:06+00:00"
---

# Breaking: #96575 - Update to CodeMirror 6 {#breaking-96575-1663324432}

See [forge#96575](https://forge.typo3.org/issues/96575)

## Description {#description}

TYPO3 Core now ships with CodeMirror v6.
CodeMirror is used as editor in the TYPO3 Backend for editing
HTML records, TypoScript templates and plaintext files in the file module.

## Impact {#impact}

Existing CodeMirror v5 addons and modes need to be adapted for CodeMirror v6
which brings a completely rewritten plugin infrastructure.

## Affected installations {#affected-installations}

TYPO3 Installations with third-party extensions that register
custom CodeMirror addons or modes.

## Migration {#migration}

Please consult [https://codemirror.net/docs/migration/](https://codemirror.net/docs/migration/) for details on
CodeMirror migration itself.

The TYPO3 integration has been adapted to reflect the changed modes and
addons in the `T3editor` configuration files:

Adapt the mode configuration in `Configuration/Backend/T3editor/Modes.php`
to use `JavaScriptModuleInstruction` statements that pick ES6 module
for a specific language mode. A RequireJS module like
`codemirror/mode/css/css` is now shipped in `@codemirror/lang-css`:

```php
use TYPO3\CMS\Core\Page\JavaScriptModuleInstruction;

return [
    'css' => [
        'module' => JavaScriptModuleInstruction::create('@codemirror/lang-css', 'css')->invoke(),
        'extensions' => ['css'],
    ],
];
```

Addons no longer bring `cssFiles` or `options`, but only consist
of a `module` and an optional `keymap` statement, as the `options`
interface is gone in CodeMirror v6 and stylesheets are to be embedded into
JavaScript.

See following example for the registration of the history addon via
`Configuration/Backend/T3editor/Modes.php`:

```php
use TYPO3\CMS\Core\Page\JavaScriptModuleInstruction;

return [
    'history' => [
        'module' => JavaScriptModuleInstruction::create('@codemirror/commands', 'history')->invoke(),
        'keymap' => JavaScriptModuleInstruction::create('@codemirror/commands', 'historyKeymap'),
    ],
];
```