Starting with Contao 4.0, we will be using semantic versioning.
What does this mean?
- Bugfix releases must only contain backwards compatible bug fixes.
- Minor releases can contain new backwards compatible features.
- Any incompatible API change must be release as a new major version.
Not everything that is backwards incompatible is also an API change! The API
includes the public and the protected methods of the Contao PHP classes, unless
they are declared as
Template files are explicitely not part of the API and thus can be changed in minor and bugfix releases, even if the change might break a customized version of the template or require to adjust CSS code to the new markup.
Using semantic versioning also means that new major version might be released more often than in the past.