Tweet Thread Splitter

How to use

1. 1Paste your long post into the input area. Add blank lines between paragraphs so the splitter has clean breakpoints to work with.
2. 2Pick a platform preset (X free, X Premium, Bluesky, Mastodon, or Threads) to set the per-tweet limit, or type a custom limit between 20 and 100,000.
3. 3Choose a numbering style: 1/n at the end, (1/n) at the start, or no numbers (best for Bluesky and Mastodon, where the reply chain is shown by the platform).
4. 4Toggle Count URLs as 23 characters on for X (matches t.co shortening) and off for platforms that show the full URL.
5. 5Read the thread preview. Each part shows its real on-platform character count and turns red if it ends up over the limit.
6. 6Use the per-part Copy button to paste each tweet in order, or use Copy all to grab the full thread as a plain text block.

About this tool

Tweet Thread Splitter turns a long post into a numbered thread of platform-sized tweets that read in order. The splitter respects natural breakpoints in priority order: blank lines between paragraphs first, then sentence-ending punctuation followed by whitespace, then single line breaks, then word boundaries, then a raw character cut as a last resort. The result keeps sentences whole whenever the per-tweet budget allows, so the thread does not break mid-thought or strand a comma at the start of the next post. Platform presets cover the four caps that actually matter for cross-posting: 280 weighted units for X (Twitter) free, 25,000 for X Premium, 300 graphemes for Bluesky, 500 characters for Mastodon, and 500 characters for Meta's Threads. A custom-limit field overrides the preset when a contract, character meter, or in-app counter calls for a different cap. Numbering style is configurable to match how the platform handles thread context: a trailing 1/n is the canonical X style, a leading (1/n) lines up vertical thread previews neatly, and a no-numbers mode is the right pick for Bluesky and Mastodon where the platform shows the reply chain on its own and a counter is redundant. For X presets, URLs are normalized to 23 weighted characters because t.co rewrites every link on send; the toggle is off by default for Bluesky, Mastodon, and Threads, where the visible URL is what counts. Wide characters (CJK ranges, Hangul syllables, fullwidth forms, the common emoji blocks, and the supplementary plane CJK extensions) count as 2 weighted units under the X rule so a Japanese, Chinese, or Korean thread fits the real platform cap and does not get truncated mid-character. Each split part shows its real, on-platform weight against the active limit, flags any part that ended up over (rare; the splitter reserves headroom for the numbering suffix up front), and ships with a per-part copy button so the writer can paste each tweet without rewriting. A copy-all button assembles the thread into a plain text block separated by --- so the whole thread can move to a draft document. Useful for newsletter authors who want to repost on X, founders writing build-in-public threads, marketers turning a blog post into a teaser thread, researchers summarizing a paper in 5 to 10 posts, and anyone who has typed a long thought into the wrong textarea and watched the character counter go red. Everything runs locally in your browser. The text you paste here is not uploaded, logged, or shared.

Free to use. Works in your browser. No signup, no login.