Shorts Safe Zone & Pre-flight Checker
Check a Short before you post it: safe-zone overlay for YouTube Shorts, TikTok and Reels, plus format, loudness (LUFS), silent intro, black opening frame, cuts and loop point. Runs in your browser.
published
- [FREE]
- [NO_SIGNUP]
- [NO_UPLOAD]
A Shorts safe zone checker that works on your actual video, not a screenshot. Drop a vertical video and it overlays the areas the YouTube Shorts, TikTok or Instagram Reels app covers with buttons and captions, then runs the checks that catch most bad uploads: aspect ratio, resolution, length, a black opening frame, silence at the start, loudness in LUFS, clipping, cuts and the loop point. Everything runs in your browser. Nothing is uploaded.
If you cut Shorts out of longer footage, the same check is built into the Video Splitter & Joiner: every clip it exports has a Check button.
What it checks
| Check | What it looks for | Why it matters |
|---|---|---|
| Aspect ratio | 9:16 vertical | Horizontal uploads are not treated as Shorts on YouTube; non-9:16 vertical gets bars |
| Resolution | 1080 px or more on the short side | 720p uploads look soft next to 1080p Shorts |
| Length | 3 minutes or less | The cap on YouTube Shorts and Reels (TikTok allows 10 minutes) |
| Opening frame | Not black, not one flat colour | The first frame is what viewers see as they swipe in |
| Silence at the start | Sound within 0.3 s | Dead air at the start gives people a reason to swipe away |
| Loudness | About −14 LUFS integrated | Quiet uploads are not turned up and sound weak in the feed |
| Peaks | Below full scale | Audio at 0 dBFS is almost certainly clipping |
| Cuts | First cut and average shot length | Approximate, shown for information |
| Loop point | Last frame against the first | Matching frames make the replay seamless |
Pass, warn and fail are deliberately conservative. Cuts and the loop point are shown as information only: plenty of good Shorts are one continuous shot or do not loop.
Safe-zone margins
None of the three platforms publishes an official safe zone for regular posts, and the guides you will find disagree. These are the margins cited most often for a 1080×1920 frame:
| Platform | Top | Bottom | Left | Right |
|---|---|---|---|---|
| YouTube Shorts | 288 px | 672 px | 48 px | 192 px |
| TikTok | 240 px | 660 px | 60 px | 140 px |
| Instagram Reels | 270 px | 670 px | 65 px | 120 px |
| All three | 288 px | 672 px | 65 px | 192 px |
The bottom margin is the big one: the title, channel name, audio credit and navigation bar take roughly the lower third of the screen. The right margin holds the like, comment, share and remix buttons. Captions placed in the usual “lower third” of a horizontal video end up under the Shorts UI, which is the most common safe-zone mistake.
Loudness, measured properly
The loudness reading follows ITU-R BS.1770, the same standard behind broadcast loudness meters and FFmpeg’s ebur128 filter: the audio is resampled to 48 kHz, K-weighted, measured in 400 ms blocks every 100 ms, then gated at −70 LUFS and at 10 LU below the average, so silence does not drag the number down. Tested against ebur128 on 22 real Shorts, every reading agreed to within 0.05 LU.
YouTube is widely measured to play videos at about −14 LUFS. Louder uploads are turned down, so pushing a mix to −8 LUFS gains nothing and loses punch. Quieter uploads are left alone, so a −25 LUFS Short plays noticeably quieter than the ones around it.
How cut detection works
Every 0.2 seconds the checker grabs a frame, shrinks it to 48×48 greyscale, and compares it with the previous one in two ways: the average pixel difference, and the shift in its brightness histogram. A cut is a jump that is big on its own and at least 2.5 times bigger than the changes around it, so a fast pan or a muzzle flash does not count as an edit. Spikes less than 0.6 seconds apart are merged into one cut.
Against FFmpeg’s scene filter on 22 gameplay Shorts, it found 14 of 16 cuts and flagged 2 moments FFmpeg did not. That is why cuts are reported as information, with approximate timings.
Privacy
The video never leaves your device. The preview plays from a local blob: URL, frames are read from a canvas, and the audio is decoded with the browser’s Web Audio API. There is no upload, no account and no watermark. You can confirm it in DevTools → Network.
Related tools
- Video Splitter & Joiner — cut a long video into Shorts-length clips, with a pre-flight check on every clip.
- YouTube Shorts & TikTok Converter — reformat any video to 1080×1920 vertical MP4.
- Video Compressor — shrink a video before sharing it.
Frequently asked questions
What is the YouTube Shorts safe zone?
It is the part of the 1080×1920 frame that the Shorts player does not cover. The like, comment and share buttons run down the right edge, and the title, channel name and audio credit sit across the bottom. The most commonly cited margins are 288 px at the top, 672 px at the bottom, 48 px on the left and 192 px on the right. Keep faces, captions and on-screen text inside that box.
Are these official YouTube, TikTok or Instagram templates?
No. None of the three platforms publishes an official safe zone for regular posts, and the published guides disagree by a hundred pixels or more. The overlay uses the margins cited most often, and the "All three" preset combines the strictest margin from each platform. Treat it as a guide and check the post in the app.
Is my video uploaded anywhere?
No. The video plays from your own device, frames are read with a canvas element and the audio is decoded with the Web Audio API, all inside the tab. Open DevTools → Network while it runs: no request carries your video.
What loudness should a Short be?
About −14 LUFS integrated. That is the level YouTube is widely measured to play videos at: louder uploads are turned down, quieter ones are not turned up. Much below −18 LUFS sounds weak next to other Shorts in the feed, and much above −10 LUFS only costs dynamics.
How accurate is the loudness reading?
It implements ITU-R BS.1770 (K-weighting, 400 ms blocks, absolute and relative gating) on the audio resampled to 48 kHz. On 22 real Shorts it matched FFmpeg's ebur128 filter to within 0.05 LU on every file.
How are cuts detected?
The checker samples five frames a second, shrinks each to 48×48 greyscale and scores how much the picture and its brightness histogram change between samples. A jump that is large on its own and large next to the motion around it counts as a cut. On 22 real gameplay Shorts it found 14 of the 16 cuts FFmpeg's scene filter found, with 2 extra, so treat cut timings as approximate.
Why does a black first frame matter?
The first frame is what people see as they swipe into your Short. Opening on black or on a fade gives them nothing to stop for. Start on the subject.
Can a horizontal video be a YouTube Short?
No. YouTube only treats square or vertical uploads of up to three minutes as Shorts. Reformat horizontal footage to 1080×1920 with the YouTube Shorts & TikTok Converter first.
Which formats can I check?
Anything your browser can play: MP4 (H.264) works everywhere, and WebM and MOV work in most browsers. Audio checks are skipped for videos over 10 minutes, which is far past every platform's cap anyway.