A TikTok video caption holds 2,200 characters and so does an Instagram caption, but that is where the likeness ends. TikTok refuses a link in a caption, advises five hashtags and cuts a photo post's title at 90 characters; Instagram refuses more than 30 hashtags and 20 mentions, and takes only pictures between 4:5 and 1.91:1. A caption written for one often breaks a rule of the other, which is the reason to know both before writing it once for both.
The figures below are what Preflight enforces when it publishes to each network through its API, checked against the code on 20 October 2026. They are the API's rules, which are not always the app's: the TikTok app takes five hashtags in its own editor, for example, and the API has no hashtag rule at all.
Captions side by side
| TikTok | ||
|---|---|---|
| Caption length | 2,200 characters on a video; 4,000 on a photo post | 2,200 characters |
| Title | A photo post shows its first line as a title, cut at 90 characters | None |
| Hashtags | No limit in the API; the app takes 5, and past 5 they only spend caption | More than 30 is refused |
| Mentions | No rule | More than 20 is refused |
| Links | Refused: TikTok's guidelines forbid a link or promotional text in what an integration shares | Counted in full, character by character |
Two details decide most captions. The TikTok link rule is a refusal, not a warning: Preflight stops the post and says why, because breaking it can lead to deleted content or a disabled account. And hashtags are the opposite way round: Instagram refuses a caption over 30, TikTok only wastes characters past five, so a caption with 12 hashtags is fine on one and weak on the other. You can count a draft against both on the character counter.
Video side by side
| TikTok | Instagram (Reel) | |
|---|---|---|
| Length | 3 seconds to 10 minutes; a creator may be held to less, often 3 or 5 minutes | 3 seconds to 15 minutes |
| File size | Up to 4 GB | Up to 300 MB |
| Format | MP4, MOV or WebM | MP4 or MOV |
| Frame rate | 23 to 60 fps | 23 to 60 fps |
| Dimensions | 360 to 4,096 pixels on each side | Ratio from 0.01:1 to 10:1, 9:16 recommended; width up to 1,920 pixels |
| What a video becomes | A video post | A Reel; the API has no other kind of video post |
The shared rule is the frame rate. Both networks take 23 to 60 frames per second, both measure it after the file is processed, and a phone recording at 120 fps or a screen capture at 15 passes the upload and fails afterwards. The file that fits both is a 9:16 MP4 at 30 fps, under 300 MB and under 3 minutes, which is why one export usually serves both. The limits pages have the full tables for TikTok and Instagram, and a file can be checked in the video checker.
Pictures side by side
Instagram feed pictures must be between 4:5 (portrait) and 1.91:1 (landscape) and are JPEG only; a phone photo at 3:4 is below the 4:5 floor and is refused, so it has to be cropped. A carousel holds up to 10 items. TikTok photo posts take up to 35 pictures, as JPEG, and the platform fetches them itself from a verified domain rather than accepting uploaded bytes, which is why a scheduler needs that domain set up before photo posts work at all. A post is a photo post or a video post on TikTok, never both: one that leads with a picture goes out as the pictures and the video is left out.
Writing one post for both
Write for TikTok first, then see what Instagram adds. Keep links out of the caption (put them in the profile), use up to five hashtags, and keep the first line of a photo post under 90 characters. That caption also passes Instagram's rules unchanged. Where you want more on Instagram, such as extra hashtags or a mention, give Instagram its own text: a scheduler that supports a different caption per network lets one video go to both with a caption each. Preflight checks both against their rules before the post leaves, and the caption preview shows where each fold falls. For the walkthrough of each network, see how to schedule TikTok posts and how to schedule Instagram posts; if a TikTok post fails, the codes are on TikTok API errors.
Questions people ask
- What is the TikTok caption limit compared with Instagram?
- Both allow 2,200 characters for a video caption. TikTok photo posts allow a 4,000-character description with a 90-character title shown from the first line. Instagram has no separate title.
- How many hashtags can I use on TikTok and Instagram?
- Instagram refuses a caption with more than 30 hashtags. TikTok's API has no hashtag limit, but its own app takes five and hashtags past five add nothing except used-up caption characters.
- Can I put a link in a TikTok caption?
- Not through the API: TikTok's content sharing guidelines forbid links and promotional text in what an integration shares. On Instagram a link in a caption is allowed and counts in full towards the 2,200 characters.
- Can one video file go to both TikTok and Instagram Reels?
- Yes, if it is an MP4 at 23 to 60 frames per second, under 300 MB and under 3 minutes, preferably 9:16. That fits both networks. Longer or larger files may fit only one.
- Why was my Instagram photo refused when TikTok took it?
- Instagram feed pictures must be between 4:5 and 1.91:1 and must be JPEG. A phone photo at 3:4 is narrower than 4:5, so Instagram refuses it until it is cropped. TikTok photo posts have no such ratio rule.