Facebook lets you write up to 63,206 characters — long enough for a short story, a multi-paragraph product update, or an event announcement complete with directions and disclaimers. Bluesky gives you 300 graphemes. That is not a trim; it is a structural rewrite. Every URL you paste into Bluesky text burns its full character length (not a flat-rate shortener), and the hashtag culture that barely exists on Facebook becomes a deliberate grapheme spend on Bluesky.
The reverse direction — Bluesky to Facebook — is usually a copy-paste. This direction forces you to decide what the post is actually about, and then say only that. This guide maps what survives the compression, what requires a full rewrite, and how SocialKit lets you maintain one source draft while keeping distinct copy for each network.
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Everything that changes between the two composers, side by side.
| Spec | Facebook (from) | Bluesky (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”) | 300 graphemes (visual characters — emoji count once) |
| Video length | Long feed uploads supported (hours); Facebook Reels are far shorter — check the composer for your account’s cap | Short clips — Bluesky has been raising limits (around 3 minutes as of early 2026) |
| Hashtags | Supported but lightly used — one or two at most reads native on Facebook | Plain-text hashtags count toward the 300-grapheme limit |
| Post length ceiling | 63,206 characters (feed truncates after a few lines with "See more") | 300 graphemes (visual characters — emoji count once) |
| Link cost in text | URLs paste as visible text; Facebook wraps them in its own preview on render | URLs count at full grapheme length — use a link card to recover the budget |
| Hashtag norms | Supported but lightly used — one or two at most reads native on Facebook | Plain-text hashtags count toward the 300-grapheme limit |
The good news
The fine print
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Tip 1
Lead Facebook posts with a standalone hook: if the first 280 characters of your Facebook post work as a complete thought, that hook doubles as your Bluesky draft and the rewrite time drops to near zero.
Tip 2
Build a link destination habit for long content: blog posts, landing pages, and event pages make Facebook posts richer and make Bluesky cross-posting trivial — the post becomes a card, not a paste.
Tip 3
Treat Bluesky threads as your long-form format: a reply-to-yourself thread lets you publish a full story across multiple 300-grapheme posts. If your Facebook update truly needs multi-paragraph depth on Bluesky, a thread is the native answer.
FAQ
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No — Bluesky’s composer will not publish a post that exceeds 300 graphemes. The post will error rather than auto-truncate. You need to actively shorten the copy to fit before publishing.
Facebook allows up to 63,206 characters; Bluesky allows 300 graphemes (visual characters, where emoji count once). That is a reduction of more than 99 percent. Think of it as moving from an article format to a headline format, not from one caption to a slightly shorter one.
Yes — unlike some platforms that use a URL shortener with a flat character cost, Bluesky counts every character of a raw URL against the 300-grapheme budget. The workaround is to attach a link card (paste the URL, let the preview attach, then delete the raw URL from the text). The card remains clickable and you recover the graphemes.
Rarely. Facebook hashtags are lightly used by the platform’s audience and often carry little discovery value. Bluesky hashtags count toward your 300-grapheme budget and drive real discovery through custom feeds and search — so use one or two that accurately describe the content rather than copying a long tag list from Facebook.
Compose once, customize the caption per network, and let SocialKit publish to Facebook, Bluesky, and 9 more platforms on schedule — no re-uploading, no copy-paste.
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