Hard caps, visible-text folds, and overflow behavior for every platform PostTruncate previews. The numbers below are the same constants the live editor checks against.
| Platform | Hard limit | Fold (mobile) | Fold (desktop) | Notes |
|---|---|---|---|---|
 LinkedIn | 3,000 | ~140 | ~210 | Text past the fold hides behind “…see more”. |
 X (Twitter) | 280 | No fold | No fold | No fold — over 280 characters splits into a thread; every link counts as 23 characters. |
 Threads | 500 | ~250 | 500 | Links count in full; copy past 500 characters chains as numbered replies. |
 Instagram | 2,200 | ~125 | ~125 | Caption folds behind “more”; aim for ~5 hashtags (hard cap 30). |
 Facebook | 63,206 | ~125 | ~480 | Feed posts collapse behind “See more” well before the technical cap. |
 TikTok | 4,000 | ~100 | ~100 | Caption folds behind “…more” at the first line break or ~100 characters; emojis and hashtags count. |
 SMS (GSM 7-bit) | 160 | No fold | No fold | 160 characters in a single message; 153 per segment once it splits. |
| SMS (Unicode) | 70 | No fold | No fold | One emoji or non-GSM character switches the whole message to Unicode. |
LinkedIn allows 3,000 characters per post but folds the feed view after roughly 140 characters on mobile and 210 on desktop — everything else hides behind “…see more”. Line breaks count, and the first sentence carries almost all of the click-through, so front-load the hook and keep links below the fold.
X enforces a hard 280-character cap per post and shows no fold at all. Every URL is wrapped by the t.co shortener and always costs 23 characters regardless of its real length, and many emoji weigh as two characters. Longer drafts must be split into a thread — PostTruncate does this automatically at word boundaries.
Threads allows 500 characters per post and, unlike X, counts links at their full length. On mobile the feed folds long posts at about 250 characters. Anything past the cap has to continue as numbered reply posts chained under the first one.
Instagram captions can run to 2,200 characters, but the feed shows only about the first 125 before the “more” link. For hashtags, ~5 is the recommended sweet spot — going higher still posts but reads as spam. The hard cap is 30 (caption plus first comment); past it the post fails to publish.
Facebook’s technical cap is 63,206 characters, but feed posts collapse behind “See more” at roughly 125 characters on mobile and 480 on desktop. Engagement drops sharply on long unbroken blocks, so the practical limit is the fold, not the cap.
TikTok allows 4,000 characters per caption when you post natively in the app, with emojis and hashtags counting in full — but the TikTok API and third-party schedulers (Buffer, Hootsuite, Later) still cap captions at 2,200, so stay under that if you don’t publish by hand. Because the video fills the screen, the feed collapses the caption behind “…more” at the first line break or about 100 characters — whichever comes first — so the opening line is all most viewers read. The video frame is full-screen vertical 9:16 (1080×1920).
A single SMS holds 160 characters in GSM 7-bit encoding, dropping to 153 per segment once the message splits. Any emoji or non-GSM character switches the entire message to Unicode — 70 characters per single message, 67 per segment — and some GSM symbols (€, brackets, the pipe) count as two.
