---
title: "Feature: #90899 - Introduce AssetRenderer pre-rendering events"
manual: "TYPO3 Core Changelog"
version: "main"
permalink: "https://docs.typo3.org/permalink/changelog:changelog-feature-90899-introduceassetprerenderingevents"
source: "Changelog/10.4/Feature-90899-IntroduceAssetPreRenderingEvents.rst"
typo3-version: "10.4"
typo3-major: 10
type: "feature"
issue: 90899
forge: "https://forge.typo3.org/issues/90899"
tags: ["PHP-API", "ext:core"]
rendered: "2026-09-20T18:31:11+00:00"
---

# Feature: #90899 - Introduce AssetRenderer pre-rendering events {#changelog-feature-90899-introduceassetprerenderingevents}

See [forge#90899](https://forge.typo3.org/issues/90899)

## Description {#description}

AssetRenderer is amended by two events which allow post-processing of
AssetCollector assets.

These new PSR-14 events are introduced:

-   `\TYPO3\CMS\Core\Page\Event\BeforeJavaScriptsRenderingEvent`
-   `\TYPO3\CMS\Core\Page\Event\BeforeStylesheetsRenderingEvent`

Both stem fom the abstract base class
`\TYPO3\CMS\Core\Page\Event\AbstractBeforeAssetRenderingEvent` and provide
these public methods:

-   `getAssetCollector(): AssetCollector`
-   `isInline(): bool`
-   `isPriority(): bool`

`inline` and `priority` refer to how the asset was registered with
[AssetCollector](https://docs.typo3.org/permalink/changelog:changelog-feature-90522-introduceassetcollector).

The events are fired exactly once for every combination of
`inline`/`priority` before the corresponding section of JS/CSS assets
is rendered by the AssetRenderer.

To make the events easier to use, the `AssetCollector::get*()` methods
have gotten an optional parameter `?bool $priority = null` which when given a
boolean only returns assets of the given priority.

> [!NOTE]
> post-processing functionality for assets registered via
> TypoScript `page.include...` or the `PageRenderer::add*()`
> functions are still provided by these hooks:
>
> -   `$GLOBALS['TYPO3_CONF_VARS'][TYPO3_MODE]['cssCompressHandler']`
> -   `$GLOBALS['TYPO3_CONF_VARS'][TYPO3_MODE]['jsCompressHandler']`
> -   `$GLOBALS['TYPO3_CONF_VARS'][TYPO3_MODE]['cssConcatenateHandler']`
> -   `$GLOBALS['TYPO3_CONF_VARS'][TYPO3_MODE]['jsConcatenateHandler']`
> -   `$GLOBALS['TYPO3_CONF_VARS']['SC_OPTIONS']['t3lib/class.t3lib_pagerenderer.php']['render-preProcess']`
>
> Assets registered with the AssetCollector (and output through the
> AssetRenderer) are not included in those.

## Example {#example}

As an example let's make sure jQuery is included in a specific version and
from a CDN.

1.  Register our listeners

    `Configuration/Services.yaml`

    ```yaml
    services:
       MyVendor\MyExt\EventListener\AssetRenderer\LibraryVersion:
        tags:
          - name: event.listener
            identifier: 'myExt/LibraryVersion'
            event: TYPO3\CMS\Core\Page\Event\BeforeJavaScriptsRenderingEvent
    ```
1.  Implement Listener to enforce a library version or CDN URI

    ```php
    namespace MyVendor\MyExt\EventListener\AssetRenderer;

    use TYPO3\CMS\Core\Page\Event\BeforeJavaScriptsRenderingEvent;

    /**
     * If a library has been registered, it is made sure that it is loaded
     * from the given URI
     */
    class LibraryVersion
    {
        protected $libraries = [
            'jquery' => 'https://code.jquery.com/jquery-3.4.1.min.js',
        ];

        public function __invoke(BeforeJavaScriptsRenderingEvent $event): void
        {
            if ($event->isInline()) {
                return;
            }

            foreach ($this->libraries as $library => $source) {
                $asset = $event->getAssetCollector()->getJavaScripts($event->isPriority())
                // if it was already registered
                if ($asset[$library] ?? false) {
                    // we set our authoritative version
                    $event->getAssetCollector()->addJavaScript($library, $source);
                }
            }
        }
    }
    ```

## Impact {#impact}

Existing installations are not affected.

If using the AssetCollector API, these new events should be used for asset
postprocessing.

## Related {#related}

-   [Feature: #90522 - Introduce AssetCollector](https://docs.typo3.org/permalink/changelog:changelog-feature-90522-introduceassetcollector)