Categories in the address book have been requested since 2001, however, they were never implemented. Outlook has them, the CardBook add-on provides them, but an implementation attempt of 2022 stalled over some UI discussion.
Some noteworthy quotes:
- We definitely want this, not sure how soon but definitely before next ESR. - 22nd Sept. 2022
- I will work on mock-ups today. - 5th Oct. 2022
Just goes to show what promises by the Thunderbird folks are worth.
We've dusted off the solution that was presented back in 2022, but it's only 40% finished. You can capture categories, as the image shows, but there are not visible elsewhere, like in the list view or in search results (Edit > Find > Search Addresses...). So if you're interested in the feature, please get in touch and pledge your financial support.
Update: We added the missing bits: List view, both as cards and table; search, both quick and advanced.
Download: Use "latest build" from the Release Notes page. It will ship officially in version 140.7.0.
Update 11th Dec. 2025: We've tested this now on a real CardDAV server at our hosting provider Hetzner with NextCloud using vCard 4.0. It works. Just for general information, here a table of what works and what doesn't:
| Provider / Server | CardDAV Support | vCard Version | Categories Support | Notes / Caveats |
|---|---|---|---|---|
| Yes | vCard 4.0 (server-side labels) | ❌ `CATEGORIES` ignored | Uses “labels” internally; any `CATEGORIES` sent by client are dropped; not visible in web UI | |
| Apple iCloud | Yes | vCard 4.0 | ✅ Preserved | Supports multiple categories per contact; fully visible in web UI and macOS/iOS clients |
| Nextcloud (old versions) | Yes | vCard 3.0 | ❌ `CATEGORIES` dropped | vCard 3.0 doesn’t formally support `CATEGORIES`; any `CATEGORIES` sent by client are likely dropped |
| Nextcloud, SabreDAV | Yes | vCard 4.0 | ✅ Preserved | Supports multiple categories per contact |
| Outlook.com / Microsoft 365 | ❌ No native CardDAV | vCard export only | ✅ Inside Microsoft ecosystem | Categories exist in Outlook desktop/web/mobile, but not exposed via CardDAV/vCard; not interoperable |