How to Cross-Post from Mastodon to Slack Automatically

Post natively on Mastodon and Ferryman automatically syncs every new post to Slack — no copy-paste, no workflow change. Set up in under two minutes.

Start cross-posting free

Why cross-post from Mastodon to Slack

Mastodon and Slack reach genuinely different audiences. Mastodon is federated, instance-driven communities — strong technical, academic, and open-source presence. Slack, by contrast, is teams and communities that use Slack channels to keep launches, updates, and shared resources visible.

A Slack channel turns published updates into timely team context without another manual copy-and-paste step. If you're already putting in the effort to write good posts on Mastodon, there's no reason that work shouldn't reach a Slack audience too — except that maintaining two presences manually is exhausting and easy to abandon. That's the problem Ferryman exists to solve.

Key differences between Mastodon and Slack

Cross-posting isn't just a copy-paste. The two platforms have different limits and conventions, and Ferryman handles each difference so you don't have to think about it.

Capability	Mastodon	Slack
Character limit	500	4,000
Images per post	4	4
Alt text on images	Yes	Yes
Video support	Yes	Yes
Native threading	Yes	No

Slack's 4,000-character limit gives you 3500 more characters than Mastodon's 500. Posts that fit on Mastodon always fit on Slack.

What gets synced

Original posts (replies and quote posts are off by default and can be enabled)
Images up to 4 per post, with alt text preserved
Videos up to platform-second length on Slack (Creator plan)
Links — Ferryman preserves URLs and link cards where Slack supports them
Hashtags and mentions are preserved as-is; platform-specific mention syntax is rewritten
Posts fit Slack's 4000-character limit without splitting

Set up Mastodon → Slack cross-posting

Sign in to Ferryman with your X account. This is how Ferryman authenticates you — you can still set Mastodon as your origin platform afterwards.
Go to Settings and connect your Mastodon account. This is the platform you'll post on natively.
Connect your Slack account in Settings. See the Slack integration guide for the exact steps.
Set Mastodon as your origin platform and check Slack as a target. Toggle cross-posting on, and Ferryman will sync new Mastodon posts to Slack within a few minutes.

Edge cases worth knowing

Skip a specific post: include #noferry anywhere in your Mastodon post and Ferryman won't sync it to Slack.
Replies and quote posts: off by default. You can enable them in Settings if you want your Mastodon conversations to appear on Slack too.
Threads on Mastodon: Slack doesn't have native threading, so Ferryman joins thread parts into a single longer post where it fits.
Editing or deleting: Ferryman doesn't propagate edits or deletions automatically. Each platform keeps its own copy once posted.
Scheduling: Use Ferryman's planner to schedule a post and Ferryman publishes to Mastodon and Slack at the same time.

Manual cross-posting vs. Ferryman

Task	Manual	Ferryman
Cross-post a new Mastodon post	Copy text, re-upload images, rewrite mentions	Automatic, within minutes
Handle character-limit differences	Rewrite or split by hand	Posts fit Slack's 4000-character limit without splitting
Preserve alt text on images	Retype every time	Carried over automatically
Skip specific posts	Remember to not cross-post	Add #noferry and you're done

Frequently asked questions

How long does it take for a Mastodon post to appear on Slack?

Ferryman checks for new Mastodon posts every few minutes and syncs them to Slack as they arrive. Most cross-posts go live on Slack within five minutes of the original Mastodon post.

What happens if my Mastodon post is too long for Slack?

Slack's 4,000-character limit gives you 3500 more characters than Mastodon's 500. Posts that fit on Mastodon always fit on Slack.

Are images and videos preserved when cross-posting from Mastodon to Slack?

Yes. Images attached to your Mastodon post are uploaded to Slack automatically, up to Slack's limit of 4 per post. Alt text is carried over so your posts stay accessible on both platforms. Videos are preserved when both platforms support them (Creator plan).

Can I cross-post one Mastodon post but skip another?

Yes. Include #noferry anywhere in a Mastodon post and Ferryman will skip syncing it to Slack (and any other connected platforms).

Does Ferryman cross-post my Mastodon replies and quote posts?

By default, only original posts are cross-posted. You can opt in to syncing replies, quote posts, or reposts from your Ferryman settings.

Is cross-posting from Mastodon to Slack free?

Every account starts with a 7-day free trial, so you can try cross-posting between Mastodon and Slack before you're billed. Cancel anytime before the trial ends and you won't be charged.

Related cross-post guides

Start cross-posting from Mastodon to Slack

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