Compatibility

MediaWiki strives to maintain broad compatibility between versions, and with a range of current and legacy software. At the same time, the constantly-evolving codebase and features of the latest MediaWiki development mean that it is not possible to maintain compatibility with legacy software indefinitely.

Browsers
There is an ever-growing number of different web browsers in the world.

Too many to actively test and support each one.

To guide our practices around browser support, we have three levels of support.

Each tier represents a different category of browsers.

Modern
This group (also known as Grade A) represents the highest level of support. Features take advantage of capabilities in modern browsers, while allowing a graceful fallback for older browsers. All features provided by the software (whether or not in a degraded form) must work in these browsers.

Browsers in this category are known (listed below) and actively tested against. Problems users perceive in these browsers are addressed with high priority.

Basic
The group (also known as Grade C) is provided the core functionality of the MediaWiki platform. Our HTTP responses are compatible with these browsers (e.g. HTTP features we rely on, character encoding, and image formats used by the content; must work in these browsers). In the front-end this means content is presented in a readable manner, and to some extent user actions can be performed.

Browsers in this category are known (listed below) and identified via [https://phabricator.wikimedia.org/diffusion/MW/browse/master/resources/src/startup.js$34 a blacklist] in the startup module.

Problems users perceive in these browsers are addressed with high priority. Issue handling focuses mainly on ensuring provided functionality is not broken; if acceptable from a product perspective, this may result in the functionality (whether or not temporarily) no longer being provided for these browsers.

MediaWiki may serve these browsers a JavaScript-less environment. The environment may lack certain visual features and extra functionality. The core functionality for these browsers must be maintained via traditional client-server interaction with full GET/POST page loads.

Unknown
This group (also known as Grade X) represents all other browsers. This includes browsers that are no longer developed or browsers not popular enough to justify the added maintenance cost for software development.

Browsers not included in any other group belong to this category.

Problems users perceive in these browsers only are given low priority.

MediaWiki handles these browsers the same as Modern (Grade A) browsers and are thus assumed to be capable. This principle provides various important benefits:
 * New versions of modern browsers may temporarily be considered Unknown if they are not yet tested against by us. Treating Unknown browsers as capable ensures optimal user experience in these browsers.
 * Users of new and evolving browsers are given a chance to have a modern experience.
 * Users of less popular browsers based on, or derived from, known modern browsers are not negatively impacted (e.g. Iceweasel).

In practice the only difference between Unknown and Modern browsers is that we don't actively test against Unknown browsers.

These browsers are given the full feature set.

Browser support matrix
While the principles and different grades described above apply to MediaWiki core and extensions alike, the below browser support matrix applies to MediaWiki core only (and extensions that decide to follow it). Individual extensions may have their own support matrix distributing browsers among the different levels of support.

Browser support matrix (mobile)
(Last updated: March 2017)

Mobile-specific skins e.g. Minerva skin provided by MobileFrontend and/or extensions designed to run on mobile devices have a different support matrix. The support matrix is compiled from the data provided by the analytics user agent breakdown dashboard. Where browser usage is over 5% a modern experience is supported. Basic support is provided for anything over 0.1% over the 12 months. In mobile a Grade B is maintained where we send modern code to browsers but do not test to the same level as A, thus we prioritise bug fixes lower.

PHP
The latest stable branch of MediaWiki () runs on any version of PHP  to PHP 7.

Please note that MediaWiki is not yet fully compatible with PHP 7.1, and will phab>phab:T153505|emit warnings, but most functionality should work as expected.

The Wikimedia Foundation runs MediaWiki on HHVM.

Features that are not used on Wikimedia wikis might not work correctly on HHVM.

MediaWiki 1.23 and 1.27 will continue to receive security updates until their respective end-of-life dates (see version lifecycle) and retain compatibility with their respective versions of PHP.

Database
MediaWiki is compatible with a variety of database servers, although support is strongest for MySQL. (MariaDB can also be used.)

Support for any other database software ranges from dubious to stable.

MediaWiki provides database abstraction layers for PostgreSQL and SQLite, which are generally well-maintained.

The included abstraction layers for Oracle and Microsoft SQL Server are essentially unmaintained and are unlikely to work out of the box.

Running MediaWiki on anything other than MySQL or MariaDB is not recommended for production use at this point.

Web server
MediaWiki is broadly compatible with all major web servers that can invoke a compatible version of PHP.

Apache is the most used and tested.

HHVM and nginx are good choices as well.