X Thread Splitter

Naive splitters cut every 280 characters and leave you with posts that end halfway through a word. This one works down a hierarchy: it keeps whole paragraphs together where it can, falls back to sentence boundaries, and only breaks on words when a single sentence is longer than the limit by itself.

It also counts the numbering. A "12/14 " prefix costs six characters, and if a thread grows from nine parts to ten, every prefix gets longer. The splitter reserves that room up front so no post silently goes over once the numbers are added.

Character counting uses the same weighted rules X applies, so emoji cost two and links cost a flat 23.

Numbering sets an expectation, which cuts both ways. "1/9" tells a reader the piece is finite and worth starting. It also tells them there are eight more posts to go, which is a reason to scroll past.

The pattern that tends to work is numbering longer threads, where the reader wants to know how much they are committing to, and leaving short ones unnumbered so each post has to earn the next on its own. If you do number, put the numbers at the start so they survive truncation.

Almost nobody reads post four of a thread they did not want to read post one of. The opening post is not an introduction, it is the entire pitch, and it should make a specific claim rather than promise that a claim is coming.

"Here is what I learned building X" promises value later. "We cut our build time from 11 minutes to 40 seconds by deleting one line" delivers it immediately and makes the next post feel earned. Write the first post last, once you know what the thread actually says.