Cascading Style Sheets (CSS) files are added as an asset library through a theme’s libraries configuration file. HTML attributes, including classes and IDs, are commonly added in template files with Twig.

In Drupal’s core library there are a number of utility functions and classes that, as a module developer, you will find make your task easier or less tedious.

Drupal's Routing API maps the URL of an incoming request to the code responsible for generating the content that is rendered in response.

Services are objects that encapsulate the code for performing specific tasks in a reusable and decoupled way.

Plugins are one of the ways that module developers can write code that extends Drupal. The Drupal Plugin API allows a module to provide functionality in an extensible, object-oriented way.

Dependency injection is a design pattern commonly used in object-oriented software architectures in order to support Inversion of Control.

A content type is a subtype of the [content entity](link to Entity topic). When a content creator goes to add new content to the site, they are presented with a list of content types to choose from to get the appropriate form to fill out.

Drupal's content moderation and workflow tools allow you to configure and support a flexible multistep publication process.

An overview of some of our favorite Drupal documentation resources.

Fields are the building blocks of Drupal's powerful content modeling system. The Field API allows for the development of custom field types to suit almost any data display and collection needs.

Many sites require the ability to upload, manage, and display various assets like files, images, videos, and audio.

A multilingual site has more than 1 language that users interact with, either through the content, the user interface, or both.

Search engine optimization (SEO) is the process of optimizing your online content, so that your content will rank higher in organic (non-paid) search engine results.

Learn to use data from your Drupal site to create customized lists in various forms, such as bulleted lists, grids, calendars, or sliders.

Debugging is the practice of troubleshooting an application through the use of tools and processes in order to find and fix bugs, or better understand the underlying code.

Drupal manages information and access for all visitors to your site, called users, through a system of roles and permissions.

Search provides internal site keyword search for content and users.

Taxonomy in Drupal provides a way to classify your site’s content. Taxonomy vocabularies are created with terms within those vocabularies.

Upgrading is the process of moving your site from a previous major version of Drupal to a newer version, for example from Drupal 7 to Drupal 11.

Content modeling consists of identifying and constructing the different building blocks of data that compose the information on your site.