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.

PHP
The latest version of MediaWiki runs on any version of PHP 5.2.3 or greater, apart from 5.3.1 which has a serious bug which renders it incompatible with MediaWiki.

The latest versions of MediaWiki contain features which are not supported by PHP 5.0 and 5.1; attempts to run with these versions will fail.

PHP 4 is unsupported since MediaWiki 1.7, and attempts to run it will fail. If you are unable to upgrade your environment to PHP 5, you must use MW 1.6; note that this release has security issues and is no longer supported by the MW community (neither is PHP 4 supported by the PHP one).

MediaWiki 1.18 and later may additionally target the HipHop compiler, which will impose a few additional constraints on compatibility and coding style.

Database
MediaWiki is compatible with a variety of database servers, although support is strongest for MySQL.

Support for any other database software ranges from dubious to stable; architectures for which classes exist have at least some support. Anything other than MySQL is not recommended for production use at this point.

Web server
MediaWiki is broadly compatible with all major web servers that can invoke PHP. Compatibility is strongest for Apache and IIS. So long as the webserver version supports the required php version based on the matrix outlined here.

Grade A
All current major web browsers are compatible with most versions of MediaWiki. "Grade A" functionality is maintained for the following browser requirements:
 * Internet Explorer 9+
 * Firefox 3.6+
 * Safari 5.0+
 * Opera 11.6+
 * Chrome 17+

Grade B
Basic compatibility is maintained for legacy versions of web browsers until they fall to a sufficiently low level of utilisation (typically under 0.01%). In particular, compatibility is currently maintained for:
 * Internet Explorer 6+
 * Firefox 2.0+
 * Safari 3.0+
 * Opera 10.0+
 * Chrome 9+

Browsers which are not explicitly marked as incompatible are often generally compatible. Support is not guaranteed for old non-standards compatible browsers and issues with those browsers might not be resolved. Security vulnerabilities affecting any browser will be addressed if possible.

Mobile browsers
In addition, MediaWiki supports reading and navigation (but not necessarily contributing) in several mobile browsers. Be aware that mobile versions of Safari, Firefox, and Opera are not quite the same as their desktop equivalents. While built on the same rendering engines, they may lack support for some features, add support for other mobile-specific features (such as touch events), or alter the display of pages to better fit on a small screen.

CSS
MediaWiki is compatible with user agents which do not process CSS3 markup. Some additional features are available to browsers which can process these styles.

JavaScript
MediaWiki is accessible to user agents which do not process JavaScript. MediaWiki degrades gracefully and all essential functionality works without JavaScript, although some things might be less convenient.

Text-only browsers
MediaWiki is accessible to text-only user agents such as Lynx, and to interpreters such as JAWS. Some functionality is reduced.

Note that older text-only browsers like Lynx are not representative of text-to-speech assistive tools like JAWS and other screen readers, which tie into browsers such as Internet Explorer and Firefox though their accessibility interfaces and make use of CSS styles, dynamic JavaScript, etc.