Deprecation: #99170 - config.baseURL and <base> tag functionality

See forge#99170

Description

The TypoScript option config.baseURL has been deprecated.

The option allowed to set a fixed URL which was then added as <base> tag to the HTML <head> part of a website. This feature was particularly useful back in previous TYPO3 versions in combination with RealURL for providing absolute links.

However, TYPO3 v9 introduced site handling, which produces absolute URLs or absolute paths directly. In addition, with TYPO3 v12.1 the option config.forceAbsoluteUrls = 1 allows to generate absolute URLs completely for all links, images or assets, making the baseURL option obsolete, as it isn't as powerful as the mentioned alternatives: It only allows to define a static value rather than loading the information based on the current request. With the TypoScript setting this is only possible with having multiple variants of config.baseURL set via TypoScript conditions.

In addition to the TypoScript option, the related public PHP methods are now obsolete and have also been deprecated:

  • \TYPO3\CMS\Core\Page\PageRenderer->setBaseUrl()
  • \TYPO3\CMS\Core\Page\PageRenderer->getBaseUrl()
  • \TYPO3\CMS\Frontend\Controller\TypoScriptFrontendController->baseUrlWrap()

Impact

Setting the TypoScript option config.baseURL will trigger a deprecation message, but will continue to work in TYPO3 v12.

Calling any of the PHP methods directly in PHP code will also trigger a deprecation message.

Affected installations

TYPO3 installations using the config.baseURL option, which is common for projects which were started before TYPO3 v9.

Migration

Use the site configuration with fully-qualified domain names to achieve the same result, as rendering a <base> tag in HTML will not be supported out-of-the-box anymore by TYPO3 v13.

If you are already using the site configuration, but need to build fully-qualified URLs, you can safely remove the TypoScript option config.baseURL without any impact in 99% of the use cases.

In special cases the option config.forceAbsoluteUrls = 1 can help you to achieve the same result.

If you need to manually set a <base> tag, this is still possible via TypoScript:

page = PAGE
page.headTag.append = TEXT
page.headTag.append.value = <base href="https://static.example.com/">
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In general, it is recommended not to use the <base> tag, as certain crawlers cannot interpret this HTML tag properly.