The Co-Authors Plus plugin makes it easy to assign one or more bylines to a post. Upon activation, you'll be able to start assigning multiple bylines right away. In order for those bylines to appear on the frontend, you may need to make some small modifications to your theme.

Assign multiple bylines to posts, pages, and custom post types via a search-as-you-type input box. Co-authored posts appear on a co-author's archive page and in their feed. Co-authors may edit the posts they are associated with, and co-authors who are contributors may only edit posts if they have not been published (as is core behavior).

For installation and activation, see the README on the repository. Once the plugin is active:

• Every post, page, and supported custom post type gains a Co-Authors box in the editor sidebar. Start typing an author's name to assign them as a byline.
• Administrators can create guest authors — bylines that aren't tied to a WordPress user account — from Users → Guest Authors. See Creating and editing guest authors for how and why.
• Once authors are assigned, your theme needs the plugin's template tags (or the Co-Authors blocks, if you're on a block theme) to display them on the front end. See Template tags and Blocks for the display side.

• Creating and editing guest authors — managing bylines that aren't tied to a WordPress user account.

• Template tags — the theme-side API for outputting co-authors in single-post templates, archive queries and feeds.
• Blocks — the Co-Authors blocks for use in the block editor, including the repeating Co-Authors block and the per-author blocks (name, avatar, biography, image).

• Hooks and filters — every filter and action the plugin exposes, grouped by what they affect.
• REST API — the canonical /coauthors/v1/coauthors endpoints, the UI-facing /coauthors/v1/authors/* routes, and the coauthors field added to core post responses.
• Roles and capabilities — the four permission questions CAP asks, which capabilities answer them by default, and the filters for remapping.

• WP-CLI commands — the full wp co-authors-plus command surface: backfills, bulk reassignment, and import helpers.
• Backfilling coauthor terms for legacy posts — a deep-dive on create-author-terms-for-posts, the most common one.

• Development and contributing — environment setup, test suites, coding standards, plugin architecture, and the release process.

• User — a WordPress user account.
• Guest author — a Co-Authors Plus author profile that is not tied to a WordPress user account. Stored as a guest-author custom post type.
• Co-author — in the context of a single post, a guest author or user assigned to the post as one of its bylines.
• Author term — a taxonomy term in the plugin's author taxonomy that links a post to one of its co-authors. One term per author; a post's co-authors are the set of terms assigned to it. Slugs use the cap- prefix (e.g. cap-ada-lovelace).
• Mapped guest author — a guest author that has been linked to a WordPress user account, so changes to the user's profile flow through to the byline.

Co-Authors Plus can be network-activated on a WordPress multisite, or on a site-by-site basis. Guest authors, author terms and guest-author mappings are all per-site — if you need the same author across multiple sites on a network, create them on each site.

If a site has a large database, you may run into issues with heavier than usual queries. You can work around this by disabling compat mode and forcing the plugin to use simpler, tax-only queries, by adding the following to your theme:

// Use simple tax queries for CAP to improve performance.
add_filter( 'coauthors_plus_should_query_post_author', '__return_false' );

This requires the site to have proper coauthor terms set up for every post — see Backfilling coauthor terms for legacy posts for the WP-CLI command that does this, including all options and examples.

If you only want to use WordPress user accounts as bylines and don't need the guest author feature, add the following:

add_filter( 'coauthors_guest_authors_enabled', '__return_false' );

This removes the Guest Authors UI and the guest-author post type.

Co-Authors Plus 4.0.0 contained a bug that could silently replace guest authors with the original post_author on authenticated REST reads that narrowed the response (for example _fields=id). It was fixed in 4.0.1. If your site ran 4.0.0 at any point, see Recovering from the 4.0.0 REST backfill regression for how to detect affected posts and recover them.

• Questions, bug reports and feature requests go on the plugin's GitHub issue tracker. Please search first; the common ones have probably been asked.
• Release history and breaking changes are documented in CHANGELOG.md.
• Pull requests are welcome. See Development and contributing for the environment setup, test suites, coding standards and release process.

Co-Authors Plus is an almost complete rewrite of the Co-Authors plugin originally developed by Weston Ruter (2007). The original plugin was inspired by the 'Multiple Authors' plugin by Mark Jaquith (2005).