TYPO3 v8 has reached its end-of-life March 31st, 2020 and is not maintained by the community anymore.
You can order Extended Long Term Support (ELTS) here: TYPO3 ELTS.
The transformation of the content can be configured by listing which transformation filters to pass it through. The order of the list is the order in which the transformations are performed when saved to the database. The order is reversed when the content is loaded into the RTE again.
Transforms the content with regard to most of the issues related to
content elements types 'Text' and 'Text & Images'. The mode is
optimized for the content rendering of the static template "content
(default)" which uses old
<font> tag style rendering.
The mode is a "hybrid" mode which tries to save only the necessary HTML in the
database so that content might still be easily edited without the RTE.
For instance a text paragraph will be encapsulated in
<p> tags while
in the database it will just be a single line ended by a line break
This transformation produces rather old style output and you should avoid it.
Like "ts_transform", but producing a modern markup.
This mode is optimized for the content rendering done by "css_styled_content".
Converts the list of preserved tags - if any - to
<span> tags with a
custom parameter 'specialtag' which holds the value of the original
Checks if any images on the page is from external URLs and if so they are fetched and stored in the uploads/ folder. In addition 'magic' images are evaluated to see if their size has changed and if so the image is recalculated on the server. Finally absolute URLs are converted to relative URLs for all local images.
Converts the absolute URLs of links to the TypoScript specific <LINK>-tag. This process is designed to make links in concordance with the typolink function in the TypoScript frontend.
Meta transformations are special modes that include several filters.
Includes the following filters: "ts_transform", "ts_preserve", "ts_images", "ts_links". Obsolete.
Includes the following filters: "css_transform", "ts_images", "ts_links". Recommended transformation. Use this for your RTE-enables fields and you should be safe.
In addition, it is possible to define custom transformations can be created allowing your to add your own tailor made transformations with a PHP class where you can program how content is processed to and from the database.