The composer first respects your explicit breaks (double newlines). Within each paragraph, it splits on sentence boundaries (.!?) and only falls back to word-level splitting if a single sentence is longer than 280 characters.
Twitter/X wraps every link through t.co, which shortens URLs to exactly 23 characters regardless of the original length. The counter follows this rule so your tweets never exceed the real limit.
When enabled, the composer reserves ~7 characters per tweet for the prefix (e.g. '(1/10) ') and prepends it after splitting. Numbering makes threads easier to read on mobile and signals the total length.
No. It's a composer/splitter only. Copy each tweet and paste it into Twitter/X, or copy the full thread as one block.
The splitter works — just note that Mastodon's default limit is 500 chars and Bluesky's is 300. Bluesky doesn't auto-shorten URLs. For strict matches, use our logic as a guide and adjust manually.