Bluesky character limit: 300 graphemes, links, media

A Bluesky post can have 300 graphemes of text, and no more than 3,000 bytes of it. A grapheme is one character as a person sees it, so a flag, a family emoji and a letter with an accent each count as one, whatever they weigh in code. Both limits are in the post schema itself, so they apply to every app and every tool that writes to Bluesky.

That one sentence is the whole answer for most posts. The rest of this page is for the cases where it is not: emoji-heavy text, long links, pictures that are too large and a video the documents disagree about. Figures checked against Bluesky's own schemas and documents on 8 October 2026.

The limits at a glance

Longer pieces go in a thread. Threads, the Meta network, has a different shape: 500 characters, with emoji counted by the byte.

What a grapheme is, and why it is not a character

A grapheme is what you would circle with a pen if asked to mark one character on a printed page. Computers store text in layers, and the layers disagree about what one character is:

• Code points are the Unicode numbers, one per building block.
• UTF-16 units are what JavaScript's .length counts.
• UTF-8 bytes are what is stored and sent.
• Graphemes are the building blocks glued together into what you see.

Bluesky's 300 is counted in the last of these. These are measured with Intl.Segmenter in Node, the same call the app and our counter use:

Three things follow. A counter built on .length calls the family emoji eleven characters, where Bluesky counts one, so it tells you to cut a post that is fine. A counter that counts emoji as two characters, as several pages on this subject do, is wrong the other way for every flag and every joined emoji. And Czech is cheap: a caption of 300 Czech letters is about 340 to 450 bytes, nowhere near the byte limit, even though every accented letter costs two bytes.

The second limit, 3,000 bytes, is the one that is almost never mentioned. It only matters when the average grapheme weighs more than 10 bytes, which is true of long joined emoji and little else. A row of 120 family emoji is exactly 3,000 bytes and 120 graphemes; the 121st is refused for its bytes although the post is nowhere near 300 graphemes. A post of 300 ordinary letters, accents and CJK included, never gets there.

The character counter counts a caption this way in your browser, per network.

Links, mentions and hashtags

Bluesky stores text as plain text. A link, a mention or a hashtag is clickable only when the post also carries a facet: a byte range of the text plus what it points to. The range counts UTF-8 bytes, not string positions, which is why the schema warns developers whose language indexes text in UTF-16. A tool that measures with the wrong unit will underline the wrong words as soon as a post contains an accent or an emoji before the link.

What each costs against the 300:

• A link counts as the text in the post. The schema says the visible URL "may have been simplified or truncated" while the facet keeps the complete address, so a client can store a short display form and link it to the long one. Preflight does not shorten anything: the address you type is the address in the text, at full length. A 75-character link counts as 75.
• A mention counts as the handle with its @. The facet names the account's permanent identifier rather than the handle, so Preflight looks the handle up first; one that does not resolve stays plain text and the post still goes out.
• A hashtag counts as the # and the word. The facet carries the tag; the schema caps a tag at 64 graphemes, and Preflight skips a tag that is longer or that is only digits.

Pages that give a fixed number for links (22 or 23 characters) disagree with each other, and neither figure appears in the schema, which is the thing that actually refuses a post. We found no rule in the lexicon that gives a link a fixed cost, and we do not claim one.

Preflight does not send a link preview card. The link is clickable and has no image under it.

What the API takes and what it refuses

Access. Preflight connects with an app password and your handle, not with OAuth. An app password is created under Settings, App Passwords, and can be revoked without touching your login. It opens a session; the session and refresh tokens are stored, not the password. The details are on the Bluesky integration.

Rate limits. From Bluesky's rate-limit guide:

The API is free to call and the guide lists no price. A schedule never approaches these; a bulk import can. The one that bites is the login limit: log in once and reuse the session. Preflight renews it rather than logging in again. A request over a limit gets a 429, and Preflight tries again later rather than at once.

What it refuses.

• Text over 300 graphemes or 3,000 bytes. The error comes from the server; Preflight stops the post before it gets there and names the number.
• A picture over 2,000,000 bytes. Bluesky refuses the upload itself. Preflight resizes to a JPEG copy up to 2,000 pixels on the long side and says so; your original is not changed.
• A fifth picture, or a picture next to a video. The post has one embed, so Preflight warns and sends what fits.
• An empty post. The schema allows empty text only when there are embeds.

The video figures disagree. Preflight accepts one MP4 up to 100 MB and 3 minutes, the limit Bluesky's app has had since March 2025. We have not found that limit in a Bluesky document we could open. The video schema now says 300,000,000 bytes, "formerly limited to 100mb", and the rate-limit guide gives 50 MB (52,428,800 bytes) as the blob size on a server. We have not tested what a 50 to 100 MB file does through a server, so we enforce the smaller of our own checks and show Bluesky's message if its server says no. If you need a rule you can rely on, keep video under 50 MB.

Scheduling. A post record has a createdAt field the client fills in, described as the time the post was originally created. It is not a publish time and nothing on the network holds a post until a date. A scheduled post is held by the tool and written when the time arrives; how scheduling works walks through it.

How Preflight checks a Bluesky post

Before a post leaves, on every plan including the free one at pricing, Preflight runs these checks and shows the result under the box, as you type:

• Text measured in graphemes against 300, with the same function in the composer and on the server, so the number you see is the number that decides.
• Text measured in bytes against 3,000, checked when the grapheme count is within bounds.
• Each thread part measured on its own against 300, with the error naming which part.
• Pictures: JPEG, PNG or WebP, at most four, each held to 2,000,000 bytes.
• Video: MP4 only, one, 100 MB and 3 minutes.
• Alt text per picture, sent with the post. No length is enforced because the schema sets none.

The same checks run through the API and, for the fields, the post reference. The connection steps are on the integration page and the scheduling walkthrough is here. Other networks, side by side, are on the limits page; for comparison, Instagram allows 2,200 characters and LinkedIn 3,000.

Bluesky's rules for automated posting

A short summary of what the platform's documents say, not legal advice:

• Scheduled posting is welcome. The bot guide says automated accounts that post at a regular interval are welcome.
• Label automated accounts. The guide says bot accounts should identify themselves with a self-label on the profile. A brand account that posts only through a tool should consider adding it.
• Respect the rate limits. The guide says bots must, and singles out logging in repeatedly as the way to trip them.
• Do not interact unprompted. The guide asks bots to like, repost or reply only to people who tagged them, and warns that unsolicited interaction may be treated as spam.
• Spam. The community guidelines are the final word on flooding people with unwanted posts and repeating posts in disruptive ways. Do not schedule the same post many times over.

Sources: post schema, rate limits and the bots guide. The wider list of what the platform asks is under "The platform's rules in short" on the integration page.

Verified 8 October 2026 against the schemas and documents above and the limits Preflight enforces. All networks: the limits page.