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Posting to Bluesky, Threads and Mastodon: what is different

Bluesky, Threads and Mastodon look alike at first: short posts, replies and reposts. Under the surface, limits, tags and etiquette differ. Here is what changes and how to adapt one idea for all three.

By the Postocial team · · 7 min read

At a glance

How the three networks compare

The main posting differences side by side. The sections below explain what each one means for your posts.

Posting limits and features on Bluesky, Threads and Mastodon
FeatureBlueskyThreadsMastodon
Text limit300 characters500 characters500 by default, set by each server
How it countsCharacters as people see them, so most emoji count as oneThe API counts emoji in bytes, so they can use more of the limitEvery link counts as 23, and only the username part of a mention counts
TagsHashtags in the text, plus up to 8 tags that do not appear in itOne topic tag per post, 1 to 50 charactersHashtags of letters, numbers and underscores
LinksLink cardsUp to 5 per postFull URLs, each counted as 23 characters
ImagesUp to 10 in the official app, 4 in the older format many apps useCarousels of 2 to 20 images and videosUp to 4 per post
VideoUp to 10 minutes and 300 MBUp to 5 minutes and 1 GBOne per post, up to 99 MB
Worth knowingA custom domain can be your handleText attachments of up to 10,000 charactersContent warnings and per-post visibility

Information as of . Sources are listed at the end of the article. Networks change their limits from time to time, so check before you rely on an edge case.

Key takeaways

  • Bluesky allows 300 characters, Threads 500 and Mastodon 500 by default, though each Mastodon server can set its own limit.
  • Tags work differently: Bluesky and Mastodon use hashtags, while Threads uses one topic tag per post.
  • Alt text is good practice everywhere, and on Mastodon media descriptions and content warnings are part of the culture.
  • Write one idea, then a version for each network. Do not paste the same text three times.

Bluesky: short posts and an identity you own

Bluesky's limit is 300 graphemes, which means characters as people see them, so most emoji count as one. It is the tightest of the three, and it rewards one clear point per post.

  • Tags: hashtags in the text become clickable, searchable tags of up to 64 characters each. A post can also carry up to 8 extra tags that do not appear in the text.
  • Images: the official app allows up to 10 images through its newer gallery format, and since June 2026 posts with five or more show as a swipeable carousel. Many other apps still use the older format, which allows 4. The app resizes images to at most 4,000 pixels on the longest side and 2 MB.
  • Video: up to 10 minutes and 300 MB, with up to 20 caption files per video so it works with the sound off.
  • Alt text: the official app allows up to 2,000 characters of alt text per image. Use it.
  • Identity: a custom domain can be your handle, such as @yourbrand.com, which shows people the account really belongs to you.

If an idea needs more than 300 characters, write a short version for Bluesky that links to the full piece, and save the detail for networks with more room.

Threads: conversational, with room for long-form

Threads posts can be up to 500 characters. Emoji can take up more of that than you expect, because the API counts them in bytes, so keep emoji-heavy posts well inside the limit.

  • One topic tag: instead of a stack of hashtags, a post gets one topic tag of 1 to 50 characters, without periods or ampersands. If a post contains several tags, only the first valid one counts, so place it on purpose.
  • Links: up to 5 per post. Since December 22, 2025, the API rejects posts with more.
  • Long-form: text attachments hold up to 10,000 characters, for writing that does not fit in a post.
  • Media: carousels of 2 to 20 images and videos, and vertical video of up to 5 minutes.
  • Replies: replies are posts too, and they keep a thread active. Plan time to answer.

Mastodon: every server has its own rules

Mastodon is not one site but many independent servers that talk to each other. Postocial connects to accounts on any server, and that independence is the main thing to plan for.

  • Limits vary: 500 characters is the default, but server admins can change it. Check your server's limits before you write long posts.
  • Links count as 23 characters, however long they are. Post the full URL, not a shortener: a shortener hides the destination and saves nothing.
  • Mentions: only the username part counts toward the limit, not the server name.
  • Hashtags: letters, numbers and underscores, but not numbers only. Write multi-word tags in CamelCase, such as #SmallBusiness, so screen readers read them correctly.
  • Media: up to 4 images, or one video, GIF or audio file per post. Describe every attachment. On Mastodon, media descriptions are a strong norm.
  • Content warnings and visibility: a content warning hides a post behind a short summary, which suits spoilers and sensitive topics. Each post can also be public, quiet public, followers-only or a private mention.

Postocial supports threads on Mastodon, for points that need more than one post, and custom thumbnails for Mastodon videos.

One idea, three versions: a worked example

Say a small web design studio wants to share a free checklist for launching a website. Here is the same idea written for each network.

Bluesky version (180 of 300 characters)

Launching a website soon? We turned our pre-launch checklist into one free page: redirects, page titles, alt text, forms, the 404 page and a final check on a real phone. #WebDesign

Threads version (333 of 500 characters)

We have launched a lot of websites, and the launch-day problems are almost never about the design.

It's the boring stuff. Missing redirects. A contact form that emails nobody. Page titles that still say Home.

So we wrote down the checklist we use on every launch and made it free. What's the one thing you always forget? #WebDesign

Mastodon version (221 of 500 characters)

New free resource: our website pre-launch checklist.

It covers redirects, page titles, alt text, forms, the 404 page and a final check on a real phone. One page, no signup, no tracking.

#WebDesign #WebDev #SmallBusiness

Notice what changed. The Bluesky version keeps only the essentials and one hashtag. The Threads version is chattier and ends with a question, because replies keep a thread active. The Mastodon version is plain and descriptive, uses CamelCase hashtags and leaves room for the link, which counts as 23 characters however long it is.

In the Postocial composer, these are three versions of one post: the same idea and schedule, with separate text for each network. Check drafts with the Bluesky character counter, or paste them into the general character counter to see several limits at once.

Etiquette that travels well

Many people on these networks are wary of accounts that only broadcast. A few habits keep a brand welcome:

  • Reply like a person. Scheduling posts is fine. Scheduling and never answering is not. On Premium and higher plans, Postocial's unified inbox collects comments from Bluesky, Threads and Mastodon in one place.
  • Do not cross-post blindly. A post that says "link in bio" or ends in a block of hashtags looks out of place on all three.
  • Describe your media. Alt text helps people who use screen readers, and anyone whose images fail to load.
  • Use content warnings where people expect them, especially on Mastodon, for spoilers and sensitive topics.
  • Keep links honest. Say where a link goes and what people will find there.

Scheduling all three from one place

  1. Connect your accounts. Mastodon works with accounts on any server. The connecting accounts guide covers each network.
  2. Write the main version, then adjust length, tags and tone for each network.
  3. Add alt text to every image.
  4. Pick your times. Mastodon timelines and Bluesky's Following feed are chronological, so timing matters more there. Our guide to finding your best time to post shows how to choose.
  5. Schedule, then watch for replies once the posts go live, in the inbox on Premium and higher plans.

Sources

Network rules, limits and specs in this article come from these pages, checked on November 1, 2026. Networks change them from time to time.

Bluesky

Threads

Mastodon

FAQ

Questions about Bluesky, Threads and Mastodon

Can I post one message to Bluesky, Threads and Mastodon at the same time?

Yes. In Postocial's composer you create one post for all three and give each network its own version, then schedule them together. Each version can fit its network's limits and conventions.

Which Mastodon servers does Postocial work with?

Any server. Because each server can change its own limits, check your server's character limit and media rules before you write long posts.

Do I need a different strategy for each network?

You need different versions, not different strategies. Keep the same themes and posting rhythm, and adapt length, tags, links and tone to each network. Then watch the replies: they show which topics each audience cares about.

Post to all three from one calendar

Write once, adapt per network and schedule Bluesky, Threads and Mastodon side by side, with replies in one inbox on Premium and higher plans.

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