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Composer is a PHP package manager. It provides functionality similar to Drupal’s native dependency management and Drush make, but for any project—not just Drupal modules. Many Drupal 8 modules depend on generic PHP packages that must be included in the site’s codebase using Composer.

Which modules have Composer dependencies?

There are several ways to determine if a module has Composer dependencies:

In addition to installing modules via the user interface, you can also download and install modules from the command line:

The recommended method for installing themes is via Composer.

Drupal 8 places all core themes in a directory named /core/themes, and all contributed or custom themes in a directory named /themes (in the webroot). Check the detailed contents of the README.txt file in the /themes directory for more information.

Most contributed modules receive periodic updates that fix security issues, resolve functionality problems, add new features, or all three. It is recommended to regularly check for new versions of the modules you use and update them as new releases become available.

The module update process is well described in the User Guide — read Chapter 13.6: “Updating a Module”.

Go to the “Extend” page if you’re not already there.

On the “Extend” page, each row in the table corresponds to one module and starts on the left with a checkbox, immediately followed by the module name.

To the right of the module name is the third column containing the module’s description.

If you don’t see the descriptions

If you don’t see the description for each module next to its name, your admin theme’s “responsive” layout is hiding them.

Some modules actually don’t require you to do anything — they simply do their job behind the scenes. However, these modules likely don’t have configurable settings or serve only as dependencies for other modules.

Most of the time, the module you’re interested in is something for which you can configure permissions and settings. Some projects are easy to use — they are “intuitive,” and it’s relatively clear what you can configure and what needs to be done to make them work as intended.

This is a temporary placeholder. Some content from the section Installing Drupal 8 Modules | Drupal 8 Guide on Drupal.org should be moved here.

To remove an unused module, you must be certain that the module is not being used on your site so that it doesn’t affect any functionality.
You can use either Drush or the administrative interface to remove modules.

Using Drush

In addition to contrib modules that have gone through the project review process, there are less strictly reviewed modules known as sandbox modules. These modules are not included in Drupal's security review process and are not packaged for download. To install them, you must clone the project’s source code using git.

Run the Update Script and “Clear All Caches”

When my site behaves oddly, shows strange errors, or displays a blank page—especially right after enabling a module—the first thing I do is refresh the page I'm on.

After that, I’ve often found that “running the update script,” followed by “clearing all caches,” solves most problems.

“Clear all caches” is a simpler and quicker fix to try, and sometimes it’s effective, so it’s the first thing I do whenever my site is giving me trouble.

This section contains documentation comparing two or more core/contributed modules that provide similar functionality. See also the module comparison page in the old documentation, which has not yet been migrated here.