The Best Open Source Alternatives to Microsoft Teams

Mattermost as a Microsoft Teams alternative

Mattermost details

Mattermost is the pragmatic exit from Teams for organisations that adopted it because it came bundled with Microsoft 365 rather than because they chose it. Channels and threads work the way a chat tool should, the desktop and mobile clients are quick, and none of it depends on a tenant, a licence count, or the rest of the Microsoft estate staying where it is.

Rocket.Chat as a Microsoft Teams alternative

Rocket.Chat details

Rocket.Chat is the closest match for what Teams is actually used for in regulated environments: internal channels, external conversations, and an audit trail, all in one deployment you host. Unlike Teams it can encrypt rooms end to end for messages, not only for one-to-one calls, and it does not route your conversations through a tenant in a jurisdiction someone else chose.

Zulip as a Microsoft Teams alternative

Zulip details

Zulip is worth a look precisely if Teams feels chaotic rather than merely disliked. Its channels are subdivided into named topics, so a thread about one incident does not get buried under an unrelated conversation, and a message can be followed weeks later without reconstructing context. It is the structural fix for the complaint people most often have about Teams channels.

Element as a Microsoft Teams alternative

Element details

Element replaces Teams with something built on an open standard rather than a vendor's tenant model. Messages are end-to-end encrypted by default — Teams encrypts only unscheduled one-to-one calls, and never chat — and because Matrix federates, other organisations can join a conversation from their own server instead of being issued guest accounts in yours.