Caption and character limits by platform, from the documented source
A caption that fits on one platform can be rejected on another, because "character" does not mean the same thing everywhere. Here is what each platform actually counts, with the document that says so.
此文章尚未提供您的语言版本，正在显示英文版本。
In short
- A character limit is not one universal number. Each platform defines its own ceiling and its own counting method.
- Some platforms count Unicode code units, some count grapheme clusters, so an emoji or a flag can cost a different amount depending on where it is posted.
- Check a real draft against every platform at once with the checker below rather than counting by hand.
280
Why the same caption can cost a different number of characters
A plain ASCII sentence costs the same everywhere. The disagreement starts with anything else: an accented letter, an emoji, a flag built from two regional indicator symbols, or a link. Some platforms count in UTF-16 code units, so a character outside the common range can cost two. Some count grapheme clusters, the units a person would actually call a character, so a family emoji built from several code points still costs one. A caption that measures fine on one platform can measure differently on another for exactly this reason, before either platform's length ceiling even enters the picture.
Links complicate the count further. Some platforms rewrite every link to a fixed width regardless of the URL's real length; others count the URL exactly as typed. A 90 character link can cost the same as a 20 character one on a platform that rewrites, and cost 90 characters on one that does not.
What each platform documents
X documents a 280 character ceiling using its own weighted counting scheme, where certain characters and every link cost a fixed 23 characters regardless of the URL's real length. Instagram documents a 2,200 character caption ceiling, counted by grapheme, with no separate weighting for a link. LinkedIn and TikTok each publish their own ceiling and their own counting rule in their API documentation, and neither matches X's scheme or each other's exactly. None of the four documents a universal Unicode standard as the rule; each states its own.
粘贴帖子正文。链接会被自动识别，以便按平台分别应用其成本。
各平台的结果
没有阻碍项，没有警告。
Why does an emoji sometimes count as more than one character?
A platform that counts UTF-16 code units, rather than grapheme clusters, charges for every code point an emoji is built from. A simple emoji is usually one code point, but a flag, a skin tone modifier or a family emoji is built from several, and a code unit counter charges for each of them.
Does a link always cost a fixed number of characters?
Only on a platform that documents a fixed link weighting. X states 23 characters for every link regardless of its real length. A platform that does not document a fixed weighting counts the URL as typed, so a long link costs more of the ceiling than a short one.
来源
- X API: Create a post 阅读于 2026年8月4日
- LinkedIn Posts API 阅读于 2026年8月4日
- Instagram Platform content publishing 阅读于 2026年8月4日
- TikTok Content Posting API 阅读于 2026年8月4日