280 is a constraint, not a vibe
A general character counter includes line breaks the same way, but it will not warn you at 280 or offer a thread. This page is built around the X composer: standard vs Premium, remaining characters, and a split when you overflow the free cap.
Emoji and most languages are counted as single graphemes so a flag or a CJK character does not surprise you the way UTF-16 length can.
When to use Premium length
Long posts are useful for a single argument. They are easy to skip. If the first 280 characters are not a complete thought, readers never reach word 2,000. Draft the opening as if you still had the old limit.
Frequently asked questions
Also useful: Instagram Character Counter · Character Counter