See what the app's interface will cover before you post
Your caption looks fine in the editor and then the app buries it under a username, a caption block and an action rail. Drop a video in below and you'll see the covered regions on your own frame — the file never leaves this tab.
Completely free & open source. No signups, no credit card required.
Your file never leaves this tab. No upload, no server-side processing, no model — the frame is read straight off your own disk.
Open your browser's network tab and you will see no file upload. What you will see: the page loads the same anonymous product analytics as the rest of this site, and the tool logs that a file was opened, which platform you picked and whether you exported. Those events never carry your file, its contents or its name.
Caption safe-zone previewer
Platform
Drop a file in to see where each app's interface will cover your frame.
OpenNolan lays captions inside these zones for you, on every export.
Every vertical feed reserves part of your frame for itself. Instagram stacks a username, a caption and an audio credit along the bottom and runs its action buttons up the right. TikTok does the same with a taller caption block. YouTube Shorts adds a title row and a progress bar. None of it is visible in your editor, which is why so much short-form ships with the punchline sitting under a share button.
This tool shows you the overlap on your own footage. Drop in a clip or a still, pick a platform, and the covered regions are masked over your frame with the safe area outlined in the middle. Then export a PNG with the masks burned in and send it to whoever is making the graphics.
It runs entirely in your browser. URL.createObjectURL hands the file straight to a <video> element — there is no upload endpoint, no analysis API and no server-side processing, so no byte of your footage is ever transmitted. (The page does load this site's ordinary anonymous product analytics; that is covered honestly in the FAQ below.) The reason is the same one that makes OpenNolan a Mac app rather than a web service: raw footage of an unlaunched product has no business on someone else's server.
Where the numbers come from
Safe-zone geometry is the whole point of a tool like this, so guessing would make it worse than useless. Two of the three platforms publish a safe-zone template you can download and measure, and that is exactly what these overlays are.
TikTok and YouTube both ship official overlay assets — TikTok as a template ZIP attached to its in-feed ad spec, Google as a transparent PNG on its YouTube video ad specs page. The rectangles here were measured out of the alpha channel of those files and scaled to a 1080×1920 frame. Instagram is different: Meta describes its safe zone in words and gives exactly one number (leave the bottom 40% clear if your Reels ad carries disclaimers), but publishes no pixel rectangle. The Instagram overlay here is therefore marked as an estimate in the tool, on the page, and in the dataset — because a confidently wrong safe zone is worse than none.
- TikTok — measured from TikTok's own In-Feed safe-zone template
- YouTube Shorts — measured from Google's own vertical safe-zone overlay PNG
- Instagram Reels — marked estimate; Meta publishes no pixel values
- Every value, source URL and verification date lives in the open spec dataset
What to do with what you see
The safe area is about half the frame. Design for that half.
The safe area is smaller than most people expect — roughly the middle half of the frame on all three platforms. That is not a reason to shrink your design into a stamp; it is a reason to be deliberate about which third of the frame carries meaning.
Put the thing the video is about in the safe rectangle and let the background bleed into the masked regions. Keep burned-in captions above the bottom block, not inside it, or the app's own caption will sit on top of yours. Keep logos and end cards off the right rail. And if your source is not 9:16, decide whether to reframe or accept the letterbox — the safe zone is measured against the full vertical frame, not against your footage.
Or skip the checking entirely
This tool tells you where the problem is. It does not fix it — you still go back to the timeline, move the text, re-export and check again.
OpenNolan places captions inside these zones as it builds the video. You drop in your clips, the agent cuts the reel, writes and positions the burned-in captions, adds B-roll and music, and exports 9:16 with the frame budget already respected. It runs natively on your Mac, your footage stays local, and you bring your own AI key. See how the agent builds a reel, or check the pacing of something you already cut with the reel pacing analyzer.
Frequently asked questions
Is my video uploaded anywhere?
No. The file is handed to a <video> element through URL.createObjectURL, which is just a pointer into your own machine's memory. There is no upload endpoint and no analysis API, so no byte of your file is transmitted — open your browser's network tab while you use the tool and you will see no file upload. To be straight about what you *will* see there: the page loads the same anonymous product analytics as the rest of this site, and the tool records that a file was opened, whether it was 9:16, which platform you selected and whether you exported a PNG. Those events never carry your file, its contents or its name.
Are these the official safe zones?
For TikTok and YouTube Shorts, yes — they were measured directly out of the safe-zone template files those platforms publish themselves. For Instagram Reels, no: Meta does not publish pixel values, so that overlay is the widely used community estimate and is labelled as an estimate everywhere it appears. The spec dataset lists every source URL and the date it was checked.
What if my video isn't 9:16?
It gets letterboxed or pillarboxed into a true 9:16 frame and the tool tells you which. That matches what the feed does. The safe zone is always measured against the full vertical frame, so bars count against you — a 16:9 clip dropped into Reels has very little usable safe area left.
Why won't my file load?
Browsers only decode a handful of codecs. ProRes, DNxHD, some HEVC variants and AV1 on older machines will fail, and the tool says so rather than spinning. Export an H.264 MP4 — what every phone records — and it will load.
Can I export what I'm seeing?
Yes. The export button draws the current frame plus the masks and the safe-area outline into a 1080×1920 canvas and saves it as a PNG, entirely locally. It is a useful thing to hand a designer or paste into a brief.