Slack is the hosted team chat tool built around channels, threads and app integrations. Its free plan hides old message history and the paid tiers are billed per user, so teams self-host to keep full searchable archives, control retention, and keep internal conversations off a third-party service.
9 open-source alternatives to Slack you can host yourself, ranked by GitHub stars and updated daily.
| # | App | Category | Stars | Language | Updated |
|---|---|---|---|---|---|
| 1 |
mattermost/mattermost
|
Chat & Messaging | 39,587 | TypeScript | today |
| 2 |
zulip/zulip
|
Chat & Messaging | 26,211 | Python | today |
| 3 |
element-hq/element-web
|
Chat & Messaging | 13,654 | TypeScript | today |
| 4 |
tinode/chat
|
Chat & Messaging | 13,565 | Go | 17d |
| 5 |
sdelements/lets-chat
archived
|
Chat & Messaging | 9,789 | JavaScript | 12mo |
| 6 |
element-hq/synapse
|
Chat & Messaging | 4,786 | Python | today |
| 7 |
msgbyte/tailchat
|
Chat & Messaging | 3,648 | TypeScript | 1mo |
| 8 |
stoatchat/self-hosted
|
Chat & Messaging | 2,684 | JavaScript | 1d |
| 9 |
DamageLabs/kandan
|
Chat & Messaging | 2,683 | TypeScript | 7mo |