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WordPress Codex

WordPress Codex: The Complete Reference for WP Site Owners

The WordPress Codex is the official manual for WordPress — covering functions, template tags, hooks, and admin guides that site owners and developers rely on when building or maintaining a WordPress site.

What it is

What is the WordPress Codex?

The WordPress Codex at codex.wordpress.org is a wiki-style reference maintained by the WordPress community. It documents everything from first-time installation to advanced plugin and theme development.

WordPress has been gradually migrating newer documentation to developer.wordpress.org, which now covers blocks, REST API, and modern theme development. The Codex remains the most complete reference for legacy topics, template tags, and classic admin workflows.

Key sections

Most-used sections of the WordPress Codex

Getting Started

Installation, first steps, and the WordPress admin interface.

Working with WordPress

Posts, pages, media, categories, menus, widgets, and users.

Template Tags

PHP functions used in themes to display dynamic content.

Plugin API

Hooks, actions, and filters — the foundation of plugin development.

Theme Development

Structure, template hierarchy, and best practices for building themes.

Security

Core hardening steps, file permissions, and login protection.

For site owners

What site owners actually need from the Codex

Most WordPress site owners reach the Codex when they encounter a specific problem: a hook they need to modify, a template tag to add, or a plugin function to understand. The most practical sections for non-developers are:

  • User Roles and Capabilities — understanding what editors, authors, and contributors can and cannot do
  • Shortcodes — how to embed dynamic content in pages and posts
  • Custom Fields — storing extra data on posts and pages
  • Hardening WordPress — the most important security steps for any site
  • Writing Posts — the full guide to post editing, categories, and tags

Codex vs developer.wordpress.org

Which reference should you use?

Use Codex for legacy admin topicsUse developer.wordpress.org for blocks and REST APIUse both for plugin development

The Codex is most reliable for WordPress 4.x–5.x era topics. For block editor (Gutenberg), block themes, and the REST API, the newer developer docs are more accurate and better maintained.

Quick reference

Codex bookmarks every site owner should have

  1. 01

    codex.wordpress.org — the main Codex index

  2. 02

    developer.wordpress.org — block, plugin, and REST API reference

  3. 03

    developer.wordpress.org/reference — full PHP function and hook reference

  4. 04

    wordpress.org/support — community forums for non-developer questions

  5. 05

    make.wordpress.org — development blogs and release notes

Common uses

When to open the Codex

  • Looking up a template tag like get_the_title()
  • Understanding a plugin hook or filter
  • Reviewing user role capabilities before adding a new user
  • Finding the right function to add to a child theme
  • Checking the correct way to register a custom post type

Common mistakes

What to watch for

  • Using deprecated functions still listed in old Codex entries
  • Copying code snippets without checking the WordPress version
  • Ignoring the newer developer.wordpress.org for block-related work
  • Adding template tag code to page content instead of theme files
  • Editing core files instead of using hooks from the Plugin API