Documents & Productivity — entry 014 of 30

Mattermost

Verified Aug 2026

Mattermost is an open-source, self-hostable Slack alternative whose REST API covers channels, posts, users, and integrations, authenticated via personal access tokens or OAuth2. The server and API are free and open-source to self-host, with paid Cloud and Enterprise tiers for managed hosting and advanced admin features.

open-sourceteam-chatself-hostedoauth
AuthenticationOAuthRequires an OAuth flow; expect app registration.
HTTPSSupportedTraffic is encrypted in transit.
CORSDisabledBrowser calls need a server-side proxy.
PricingFreemiumA usable free tier exists, with paid plans for more volume.
FormatsJSONResponses can be requested as JSON.

GreatAPIs Score

Score54out of 100
Authentication8/25OAuth flow required
Pricing17/20Freemium tier available
Docs0/20No docs or spec available
Formats9/15Single response format
Freshness20/20Verified within 6 months

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Scored 54 on greatapis.com
<a href="https://greatapis.com/api/mattermost/"><img src="https://greatapis.com/badge/mattermost.svg" alt="Scored 54 on greatapis.com"></a>

Auth quickstart

  1. Register an app / run the OAuth flow to obtain a bearer token.
  2. Send it as an Authorization headerAuthorization: Bearer <token>
Stored keyNo key stored

Your key is stored only in this browser (localStorage) and sent directly to the API — never to greatapis.