OneTaskBy Tim King · Updated
Social Video Spec Checker
Will Your Video Upload to TikTok, Reels or X?
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How the Social Video Spec Checker works
This social video spec checker tells you whether a clip will upload and display well before you post it. Drop a video, pick the platform, and each limit is checked: format, length, file size, aspect ratio and resolution. Change the platform to compare. The file is read in your browser.
Upload failures are rarely explained well. A post stalls at 99%, a Reel is rejected as "unsupported" or an ad is bounced by review a day later. Almost every case comes down to one of five things, and all five can be read from the file before you try.
What the social video spec checker tests
| Check | What fails it | Fix |
|---|---|---|
| Format | A container the platform does not take, such as .mkv on X | Re-export as MP4 |
| Length | Over the cap for that account or placement | Trim, or split into parts |
| File size | Over the platform's published limit | Lower the bitrate, not the size |
| Aspect ratio | Outside the allowed range, such as 2.35:1 for a Reel | Crop or pad to the range |
| Resolution | Short side under the minimum, or a side too long | Resize the video |
A sixth line, Fills the screen, is advice rather than a rule. It compares the clip's shape with the shape that fills the platform's player: 9:16 for Reels, Shorts and TikTok, 16:9 for YouTube, X, LinkedIn posts and Facebook. Anything else uploads, but is shown with bars or cropped.
Where the limits come from
| Platform | Max length | Max size | Shape |
|---|---|---|---|
| Instagram Reel | 3 minutes | Not published | 1.91:1 to 9:16, 720 px+ |
| TikTok upload | 60 minutes | Not published | Any; 9:16 fills |
| TikTok in-feed ad | 10 minutes | 500 MB | 9:16, 1:1 or 16:9 |
| YouTube Shorts | 3 minutes | 256 GB | Square or vertical |
| YouTube (verified) | 12 hours | 256 GB | Any; 16:9 fills |
| X free account | 140 seconds | 512 MB | Shown at up to 1080p |
| X Premium (web, iOS) | 4 hours | 16 GB | Shown at up to 1080p |
| LinkedIn post (desktop) | 15 minutes | Not published | Any |
| LinkedIn video ad | 3 s to 30 minutes | 500 MB | 9:16 to 16:9, 360–1920 px |
| Facebook feed video | Under 4 hours | 10 GB | Any |
These match the platforms' own help pages as listed in the video upload limits table. Where a platform publishes no file size limit, the checker says so instead of guessing. Limits change and are sometimes rolled out to some accounts first, so a borderline result is worth a test upload.
Tips and pitfalls
Size problems are bitrate problems. A file over the limit almost always has a higher bitrate than the platform will keep. Re-encode at a lower bitrate; the platform would compress it anyway.
Phone clips report the turned size. Your browser applies the phone's rotation flag, so a vertical phone clip reads as 1080 × 1920, which is what platforms see too.
Variable frame rate. Screen recordings and some phone clips use a variable rate, which a few platforms reject or play out of sync. Check it with the video info inspector.
How to read the result
The verdict counts the hard failures. Each line then says Pass, Fail or Check, with the measured value and the limit. Check means the platform sets no rule, or the point is advice only.
FAQ
What are Instagram Reels video requirements?
An MP4 or MOV up to 3 minutes long, with an aspect ratio between 1.91:1 and 9:16 and a short side of at least 720 pixels. A 1080 × 1920 vertical clip at 30 fps fills the screen and is the safest choice for a Reel.
Why is my video too big to upload?
Its bitrate is higher than the platform needs. A 10-minute 4K phone clip can pass 3 GB. Re-encode it at around 8 to 10 Mbit/s for 1080p and the same clip drops to well under 1 GB with little visible loss once the platform compresses it.
Does the checker upload my video?
No. The file is opened by your browser only to read its length, size and dimensions. Nothing is sent to a server or to any of the platforms named here, so you can check unreleased videos safely.
Why does it say Check for file size?
Instagram, TikTok and LinkedIn posts do not publish a file size limit. The checker shows the size so you can judge it, but does not invent a limit. Very large files can still time out on slow connections, so trim or compress if the upload stalls.
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