vBulletin is commercial forum software written in PHP. It powered a large share of the web’s big forums through the 2000s and is still sold and developed.
How it models content
- Forums hold threads and can be nested
- Threads hold posts
- Posts are individual replies
- Users with usergroups and permissions
Counters matter here. vBulletin stores running totals for post counts, thread counts and last-post details rather than counting live, so after an import or a direct database change those figures can be wrong. See rebuilding vBulletin forum data.
Versions are not interchangeable
There are separate lines of vBulletin with different architectures, and add-ons for one will not work on another. If you are dealing with an existing install, establish which line it is on before planning anything. It changes what is possible.
What moves cleanly
- Threads, posts and users transfer to most other forum software
- Private messages sometimes transfer, depending on the destination
- Attachments may be in the database or on disk, and you need to know which
- Usergroup permissions rarely map. Plan to rebuild them.