1# THIRD-PARTY MODULES 2 3Many webtrees functions are provided by “modules”. 4Modules allows you to add additional features to webtrees and modify existing features. 5 6## Installing and uninstalling modules 7 8A module is a folder containing a file called `module.php`. 9There may be other files in the folder, such as CSS, JS, templates, 10languages, data, etc. 11 12To install a module, copy its folder to `/modules_v4`. 13 14To uninstall it, delete its folder from `/modules_v4`. 15 16Note that module names (i.e. the folder names) must not contain 17spaces or the characters `.`, `[` and `]`. It must also have a 18maximum length of 30 characters. 19 20TIP: renaming a module from `<module>` to `<module.disable>` 21is a quick way to hide it from webtrees. This works because 22modules containing `.` are ignored. 23 24## Writing modules 25 26To write a module, you need to understand the PHP programming language. 27 28There are several example modules available at 29https://github.com/webtrees 30 31The built-in modules can be found in `app/Module/`. 32These contain lots of useful examples that you can copy/paste. 33