---
title: "Deprecation: #63974 - Deprecate CSS compressor callback method"
manual: "TYPO3 Core Changelog"
version: "main"
permalink: "https://docs.typo3.org/permalink/changelog:deprecation-63974"
source: "Changelog/7.4/Deprecation-63974-CssCompressorCallbackAndCompressCssString.rst"
typo3-version: "7.4"
typo3-major: 7
type: "deprecation"
issue: 63974
forge: "https://forge.typo3.org/issues/63974"
tags: ["PHP-API"]
rendered: "2026-09-17T12:41:04+00:00"
---

# Deprecation: #63974 - Deprecate CSS compressor callback method {#deprecation-63974-deprecate-css-compressor-callback-method}

See [forge#63974](https://forge.typo3.org/issues/63974)

## Description {#description}

The callback method `compressCssPregCallback()` as defined in
EXT:core/Classes/Resource/ResourceCompressor.php has been marked as deprecated due to the overhauled regular expressions.

## Impact {#impact}

Usage of the mentioned method is discouraged and will break as of CMS 8.

## Affected installations {#affected-installations}

All installations or extensions using the `compressCssPregCallback()` callback method.

## Migration {#migration}

No migration possible for the callback method.