Paste a long post and the Twitter Thread Builder splits it into a numbered thread where every tweet fits the character limit — no manual counting, no words cut in half.
How the splitting works
The builder packs your text greedily, one word at a time, into tweets of at most your chosen limit (280 by default). A word is only ever broken if the single “word” is itself longer than the available space — otherwise breaks always land on whitespace. URLs are measured as 23 characters regardless of their real length, because Twitter shortens every link through t.co. That means a thread full of links won’t silently overflow.
If you choose a numbering style, the builder reserves space for the label before packing. Because the total tweet count can change once numbering is added, it re-packs until the count is stable — so a 12/12 label never tips the last tweet over the edge.
Forcing your own breaks
Want a tweet to end at a specific spot — a punchline, a section heading, a code block? Put a line containing only --- where you want the break. Everything before it becomes its own run of tweets, and everything after starts fresh.
Privacy
Everything runs in your browser. Your draft is never uploaded, logged, or sent to any server — open DevTools then Network and you’ll see zero requests while you type. When you’re done, copy a single tweet or the entire thread and paste it into X or your scheduler of choice.
Related tools
Check a single tweet’s exact length with the Twitter Character Counter, tune your tags with the Hashtag Analyzer, or style standout text with the Unicode Text Styler.