Free tool
Video spec checker
Drop a video and see whether it will post to Instagram Reels, TikTok, YouTube Shorts, Facebook Reels, LinkedIn, X (Twitter), Threads and Bluesky. Each platform gets a pass, a warning or a fail, the reason in plain words and the fix. The check runs in your browser, so the file never leaves your device.
Video specs by platform
What each platform publishes for video, next to what Socialync posts. Pick a platform for its full specs.
| Platform | Size and shape | Length | File size | Formats | Socialync posts |
|---|---|---|---|---|---|
| Instagram Reels | 9:16 recommended, at least 720 pixels | 3 seconds to 15:00 | Up to 300 MB | MP4 and MOV | Up to 3:00, files up to 4 GB |
| TikTok | 360 to 4,096 pixels on each side | Up to 10:00 | Up to 4 GB | MP4, WebM and MOV | Up to 3:00, files up to 4 GB |
| YouTube Shorts | Vertical or square, up to 1080p | Up to 3:00 | Up to 256 GB | MP4, MOV, WebM, AVI and more | Up to 3:00, files up to 4 GB |
| Facebook Reels | 1080x1920 (9:16) recommended | No limit | Not published | MP4 and MOV | Up to 3:00, files up to 4 GB |
| 256x144 to 4096x2304 | 3 seconds to 15:00 | 75 KB to 5 GB | MP4, MOV, AVI, WebM and more | Up to 3:00, files up to 4 GB | |
| X (Twitter) | 720x1280 recommended for vertical | 0.5 seconds to 2:20 | Up to 512 MB | MP4 and MOV | Up to 2:20 without X Premium, files up to 512 MB |
| Threads | 9:16 recommended, up to 1,920 pixels wide | Up to 5:00 | Up to 1 GB | MP4 and MOV | Up to 5:00, files up to 1 GB |
| Bluesky | Not published | Up to 10:00 | Up to 300 MB | MP4, MPEG, WebM and MOV | Up to 10:00, files up to 300 MB |
Platform numbers come from each platform's own help and developer pages, checked October 11, 2026. Socialync's numbers are the limits it checks before it publishes.
- Instagram Reels: Instagram API reference, Reel specifications, Instagram Help Center, reel size and aspect ratios, Instagram Help Center, reel length
- TikTok: TikTok Content Posting API, media transfer guide
- YouTube Shorts: YouTube Help, three minute Shorts, YouTube Help, get started with Shorts, YouTube Help, upload size and length, YouTube Help, supported file formats
- Facebook Reels: Facebook Help Center, what are reels, Meta Newsroom, making it easier to create videos on Facebook, Meta for Developers, Reels publishing guide, Facebook Help Center, video file formats
- LinkedIn: LinkedIn Help, video specifications
- X (Twitter): X Help Center, videos on X, X developer docs, media best practices
- Threads: Threads API overview, video specifications
- Bluesky: Bluesky app source, video limits, AT Protocol lexicon, video embed
Frequently asked questions
Does the checker upload my video?
No. Your browser reads the file size, type, length and frame size on your device, and nothing is sent anywhere.
How long a video can Socialync post?
Up to 3:00 on Instagram, TikTok, YouTube, Facebook and LinkedIn. Up to 5:00 on Threads. Up to 10:00 on Bluesky. On X, up to 2:20 for accounts without X Premium.
What size should a vertical video be?
Instagram Reels, Facebook Reels and Threads recommend 9:16. A Short is vertical or square and uploads at up to 1080p, which is 1080x1920 in 9:16. Meta recommends 1080x1920 (9:16) for reels, and at least 540x960.
Is this the same check Socialync runs?
Yes. The verdict comes from the same preflight Socialync runs before it publishes, which is also what AI assistants call through the validate_post tool on Socialync’s MCP server.
What if the checker cannot read my video?
Some browsers cannot play HEVC (H.265) video, which iPhones record when the camera is set to High Efficiency. The checker still checks the file size and says what it could not read. Open the page in Safari, or export the video as an H.264 MP4, to check everything.