If you limit the list to open-source forum software that is still actively maintained, a relatively small set dominates today. Many classic packages still exist, but only some have active development and modern stacks.
Below are the most widely used and actively maintained open-source forum platforms as of ~2025–2026.
Major actively maintained open-source forum software
1. Discourse
Language: Ruby (Rails) + PostgreSQL
Style: Modern discussion platform (not classic forum UI)
- Very active development by the Discourse team.
- Used by large communities (many tech companies and open-source projects).
- Real-time interface, infinite scrolling, notifications, trust system.
- Requires more server resources than traditional PHP forums.
Pros
- Modern design and features
- Very strong moderation tools
- Active ecosystem
Cons
- Heavy stack (Ruby + Redis + PostgreSQL)
- Not traditional forum layout.
2. phpBB
Language: PHP
Style: Traditional forum
- One of the oldest and most widely deployed forum packages.
- Still actively maintained by the phpBB Group.
- Classic threaded forum style.
Pros
- Extremely mature
- Large extension ecosystem
- Easy hosting (LAMP stack)
Cons
- Old architecture
- UI feels dated without themes.
Market share data still places phpBB among the top open-source forums globally. (Webmaster Tips)
3. Flarum
Language: PHP + JavaScript/TypeScript
Style: Modern minimalist forum
- Created from merging FluxBB and esoTalk projects.
- Focused on lightweight core + extensions.
- Active development; latest releases continue through 2025. (Wikipedia)
Pros
- Modern UI
- Lightweight compared to Discourse
- Very clean codebase
Cons
- Smaller extension ecosystem than phpBB.
4. NodeBB
Language: Node.js
Style: Modern, real-time forum
- Uses WebSockets for live updates.
- Can run on Redis or MongoDB.
- Actively developed and used by many communities.
Pros
- Real-time posts
- Modern architecture
- Good plugin ecosystem
Cons
- Requires Node stack (not typical shared hosting).
5. MyBB
Language: PHP
Style: Traditional forum
- Open-source forum system originally released in 2002.
- Supports MySQL, MariaDB, PostgreSQL, and SQLite. (Wikipedia)
Pros
- Familiar classic forum design
- Good plugin ecosystem
- Easy hosting
Cons
- Development slower than newer platforms.
6. Simple Machines Forum (SMF)
Language: PHP
Style: Traditional forum
Pros
- Mature and stable
- Lightweight
- Good moderation tools
Cons
- Smaller developer activity than phpBB or Flarum.
Other projects still alive but smaller
These exist but are less common:
- FUDforum – older PHP forum, still maintained but niche. (Wikipedia)
- Vanilla Forums (open‑source version) – original open source version exists, though the commercial SaaS dominates.
- FluxBB – lightweight but slow development.
Rough popularity tiers (open-source only)
Tier 1 (most active ecosystems)
- Discourse
- phpBB
Tier 2 (modern but smaller)
- Flarum
- NodeBB
Tier 3 (traditional but quieter)
- MyBB
- SMF
