Overview
Mattermost-Bot is the crawler Mattermost uses when a workspace generates a website link preview. Paste a URL into a channel and the Mattermost server fetches the page, reads the metadata, and builds the preview shown under the message.
The important detail is that Mattermost is usually self-hosted. The request may come from a company server, a cloud VM, or a private network, not a single central Mattermost crawler fleet. If your server logs show Mattermost-Bot, treat it like a legitimate link preview fetch.
Mattermost admins can turn link previews off or restrict previews for specific domains. That changes debugging compared with Facebook or LinkedIn. The page can be correct and still show no preview because the workspace configuration blocks it.
User-Agent String
Mattermost Bot identifies itself with the following user-agent string:
Mattermost-Bot/1.1How Mattermost Bot Handles OG Images
Mattermost fetches website metadata for link previews. Standard Open Graph tags are the safest target.
Meta Tags Read
og:imageog:titleog:descriptionog:urlog:site_name| Preferred Size | 1200 × 630 |
| Minimum Size | No public strict minimum |
| Cache Duration | Not publicly documented |
Caching Behavior
Server/workspace-level behavior. Mattermost does not provide a public cache debugger; changing the URL with a query parameter is the practical way to force a fresh fetch.
Fallback Behavior
If OG tags are missing, Mattermost may still show a basic title or text preview when it can read the HTML. Without an accessible image URL, expect a text-only preview.
Things to Know
- The fetch comes from the Mattermost server, so private network access, firewalls, and outbound proxy rules matter.
- Workspace admins can disable link previews globally or restrict previews for selected domains.
- Self-signed or broken TLS certificates can prevent previews from working.
- Because Mattermost is self-hosted, source IPs vary by installation. User-agent detection is more useful than IP allowlisting.
robots.txt
Allow Mattermost-Bot if you want Mattermost workspaces to generate rich previews for your links. Blocking it can make shared links appear as plain URLs or text-only previews.
User-agent: Mattermost-Bot
Allow: /How to Test
Mattermost has no public debugger. Test by pasting the URL into a Mattermost channel where website link previews are enabled.
- Check server logs for Mattermost-Bot/1.1 after pasting the URL.
- If no request appears, ask the workspace admin whether website link previews are enabled or restricted for your domain.
- Append a query parameter (e.g., ?v=2) after changing OG tags to avoid reusing a cached preview.
- Make sure the Mattermost server can reach both the page URL and the og:image URL over HTTPS.
You can also use the MyOG OG Preview tool to check how your OG tags are configured before testing with Mattermost Bot.
FAQ
What is Mattermost-Bot?
Mattermost-Bot is Mattermost's link preview crawler. When someone shares a URL in a Mattermost channel, the Mattermost server can fetch the page and read its metadata to generate a preview.
Why is Mattermost-Bot hitting my site?
Someone likely shared your URL in a Mattermost workspace with website link previews enabled. The request is part of link unfurling, similar to Slackbot or Discordbot.
How do I fix a missing Mattermost link preview?
Check that the page has absolute HTTPS Open Graph tags, the og:image URL is public, the Mattermost server can reach your site, and the workspace has website link previews enabled for your domain.
Related Bots
Test Your OG Images
Check how your Open Graph images appear to bots and crawlers. Preview your link cards before sharing.
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