Character Limits Across Platforms: Twitter/X, SMS, and More

X (Twitter)

• Standard post: 280 characters. X Premium subscribers can post up to 25,000.
• Bio: 160 characters — coincidentally the same length as a classic SMS.
• Display name: 50 characters. Username: 15 characters.
• Direct messages: 10,000 characters.

X uses a weighted counting system, not a simple one-character-per-letter count: most Latin characters count as 1, but emoji and CJK (Chinese, Japanese, Korean) characters count as 2 each. Any URL, regardless of its actual length, is shortened and counted as exactly 23 characters. This is why a post that visually looks well under 280 characters can still be flagged as too long — the weighting adds up faster than it appears.

SMS

A traditional single SMS message is limited to 160 characters. This historical limit is actually the origin of Twitter's original 140-character cap — the platform reserved 20 characters out of a 160-character SMS for a username, leaving 140 for the message itself, since Twitter originally supported posting via text message.

Meta Descriptions (SEO)

Search engines typically display roughly 150-160 characters of a meta description before truncating it with an ellipsis, though the exact cutoff varies by device and by how wide individual characters render. Keeping a meta description within that range helps ensure the full intended text displays in search results.

Instagram

• Caption: 2,200 characters, though typically only the first roughly 125 characters show before a "more" link.
• Bio: 150 characters.

The General Pattern

Most character-limited platforms exist for practical reasons — SMS was constrained by the underlying protocol, while social platforms often use limits deliberately to encourage concise writing. Checking your text against the specific platform's actual limit, ideally accounting for weighted counting where it applies, avoids an unpleasant surprise when publishing.