Facebook to Mastodon is the cliff direction for text: Facebook posts can run to 63,206 characters — long essays, event recaps, link roundups — while Mastodon’s default cap is 500, enforced by the server and non-negotiable unless your target instance has been configured to allow more. That means a typical long Facebook post must be cut by 99% or rebuilt as a thread, making the caption rewrite the central task, not an afterthought.
The culture inverts just as sharply. Facebook’s light touch on hashtags (one or two at most reads native) becomes a problem on Mastodon, where most servers run no algorithmic feed — hashtags are the primary way new readers encounter a post. Bringing a Facebook mindset straight to Mastodon means arriving with great content that almost nobody can find.
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Everything that changes between the two composers, side by side.
| Spec | Facebook (from) | Mastodon (to) |
|---|---|---|
| Primary canvas | 1080 × 1350 px · 4:5 (post) | 1200 × 675 px · 16:9 (post image) |
| Caption limit | 63,206 characters (feed truncates after a few lines with “See more”) | 500 characters by default — instance admins can raise it |
| Video length | Long feed uploads supported (hours); Facebook Reels are far shorter — check the composer for your account’s cap | Instance-dependent; default upload caps are modest, so keep clips short |
| Hashtags | Supported but lightly used — one or two at most reads native on Facebook | Count toward the limit and drive most discovery (most instances have no algorithmic feed) |
| Caption cliff | 63,206 characters (feed truncates after a few lines with "See more") | 500 characters by default — instance admins can raise it |
| Hashtag role | Supported but lightly used — one or two at most reads native on Facebook | Count toward the limit and drive most discovery (most instances have no algorithmic feed) |
| Link URL visibility | URL can be removed from copy once the preview card attaches | URL stays visible and counts toward the 500-character limit |
The good news
The fine print
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Tip 1
Write the Mastodon post first, not last: starting with the 500-character constraint forces you to find the sharpest version of the idea, and the longer Facebook post almost writes itself from the leftover context.
Tip 2
Use CamelCase hashtags for accessibility: #OpenSource reads more naturally with a screen reader than #opensource, and Mastodon’s culture genuinely cares — leading with accessible formatting also signals that you understand the community.
Tip 3
Check whether your target instance raises the limit: some subject-specific Mastodon servers (tech, academia, art) run with limits above 500 — if you’re posting to one of those, confirm the actual character budget before you cut.
FAQ
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Almost certainly not without heavy editing. Facebook allows up to 63,206 characters while Mastodon’s default cap is 500 — some instances raise the limit, but you must confirm the target server’s actual setting. The only path for long content is a deep rewrite or a thread where each reply carries one idea within the 500-character budget.
Yes, for reach. On Facebook, the algorithm surfaces posts to people who don’t follow you; most Mastodon instances run no equivalent algorithmic feed. Hashtags are how new readers encounter your content — 3–6 specific, relevant tags placed at the end of the post is the standard practice on most servers.
Mastodon does generate Open Graph preview cards, but the behavior depends on the instance — some servers enable it, some don’t. Unlike Facebook, where you can remove the URL text once the card appears, the URL in a Mastodon post remains visible and counts toward your 500-character limit. Budget for it.
Not through any native Facebook export — the platforms have no direct bridge. A scheduler like SocialKit lets you compose once and publish to both networks, with separate captions per network so the Facebook version keeps its full length while the Mastodon variant is rewritten to fit the 500-character default and adds the hashtags Mastodon discovery depends on.
Compose once, customize the caption per network, and let SocialKit publish to Facebook, Mastodon, and 9 more platforms on schedule — no re-uploading, no copy-paste.
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