mimicWhat it checks
- 1
Length
Read from the file's metadata, to the hundredth of a second.
- 2
Resolution and shape
The decoded frame size, the ratio (9:16, 4:5…) and whether it's vertical.
- 3
Frame rate
Estimated by playing one second muted and offscreen and timing the frames your browser shows.
- 4
Size and bitrate
File size from your device; average bitrate is size × 8 ÷ length.
- 5
Platform fit
Each number against 8 sets of upload rules: green fits, amber needs a look, red won't upload.
The limits it checks against
Each limit comes from the platform's own help, developer or ads page, checked on October 28, 2026.
| Platform | Max length | Max file | Shape |
|---|---|---|---|
| TikTok (TikTok Studio upload) | 30 min | 10 GB | Not stated; 720×1280 or higher |
| TikTok (posted from another app) | 3 min | 4 GB | Any; 360 to 4096 px per side |
| TikTok In-Feed ad (non-Spark) | 10 min | 500 MB | 9:16 (recommended), 16:9 or 1:1; 9:16 at least 540×960 |
| Instagram Reels | 20 min | not stated | Between 9:16 and 1.91:1 |
| Instagram Reels ad | 15 min | 4 GB | 9:16 (1440×2560 recommended) |
| YouTube Shorts | 3 min | not stated | Square or vertical |
| YouTube (regular video) | 12 h | 256 GB | Any; 16:9 is standard |
| LinkedIn post | 15 min | 5 GB | Between 1:2.4 and 2.4:1 |
Why the frame rate is an estimate
Browsers don't expose a video's frame rate directly. The checker times about 40 frames as they're presented and takes the median gap, then snaps to a standard rate (23.976, 24, 25, 29.97, 30, 50, 59.94, 60) if it's within 3%.
iPhone and Android footage is often variable frame rate, and a busy computer can drop frames, so treat it as close. A media tool like MediaInfo reads the exact value from the file.
Worked example
A 1080×1920 clip, 2 min 10 s, 30 fps, 310 MB.
TikTok Studio: fits (under 30 min, under 10 GB, at least 720×1280).
Instagram Reels: fits, and under 3 minutes, so it can be recommended to new audiences.
YouTube Shorts: fits (vertical, under 3 minutes).
TikTok In-Feed ad: fits (under 10 min, under 500 MB).
Sources
- TikTok Support, Creator tools on TikTok (TikTok Studio upload requirements)
- TikTok for Developers, Content Posting API: media transfer guide (video restrictions)
- TikTok Ads Help, Auction In-Feed ad specifications (In-Feed Standard safe zone file, 720×1280)
- Instagram Help Center, Record a reel (up to 20 minutes; over 3 minutes not recommended to new audiences)
- Instagram Help Center, Reel size and aspect ratios
- Meta Ads Guide, Instagram Reels video ads (safe zone, size, length)
- YouTube Help, Shorts up to three minutes (square or vertical)
- YouTube Help, Upload videos longer than 15 minutes (256 GB or 12 hours)
- LinkedIn Help, Video sharing troubleshooting (video specs)
Questions
Is my video uploaded?
No. The browser opens the file from your device with a local link, reads its details and plays a second of it muted and offscreen. Nothing is sent anywhere.
Why can't it read my .mov file?
Your browser has to be able to decode the video to measure it. iPhone .mov files are usually HEVC (H.265), which Safari plays and other browsers play only on some computers. Try Safari, or export as H.264 MP4.
How long can a TikTok video be?
TikTok Studio uploads can be up to 30 minutes and under 10 GB. Videos posted to TikTok from other apps are limited to 3 minutes for every creator, with 5 or 10 minutes for some accounts.
How long can an Instagram Reel be?
Up to 20 minutes, but Instagram says reels over 3 minutes won't be recommended to new audiences.
What makes a video a YouTube Short?
A square or vertical video up to 3 minutes long, uploaded after October 15, 2024. Anything longer or wider is a regular video.
What's a good bitrate?
YouTube recommends 8 Mbps for 1080p at 24–30 fps and 12 Mbps at 48–60 fps. The video file size calculator has the full table.