How Short-form Preflight works

The problem it checks

A subtitle or caption you position for one short-form platform can land somewhere different on another. YouTube Shorts, Instagram Reels and TikTok each draw their own UI — buttons, captions, usernames — in slightly different places over the same 9:16 video frame. A subtitle that clears one platform's UI can still sit under another's action rail or caption block. This tool checks one placement against all three at once, instead of you guessing per platform.

Step by step

1. Load local media. Choose an image or video from your device. It's read with a browser File object and shown via a local Object URL — nothing is sent anywhere. See Privacy for the full explanation.
2. One Subtitle, three previews. A single rectangle — the Subtitle — is drawn on identical copies of your media in three preview frames, one per platform. Drag, resize, or nudge it with arrow keys in any one preview and all three update together, because it's one shared position and size, not three separate ones.
3. Per-platform collision check. Each platform has a set of reference regions taken from documented evidence, not guesswork — measured UI areas for Reels and TikTok, and a published source's edge margins for Shorts (see the platform guides). The tool checks whether the Subtitle's rectangle overlaps or comes within a small margin of each region, and reports Safe, Warning, or Overlap per platform, with the specific region named.
4. Find safer position. If any platform isn't Safe, this searches for the nearest position — same size, not shrunk or stretched — that clears every platform's regions at once. If no such position exists for the current size, it says so and suggests resizing, rather than silently picking something that still overlaps.
5. Adjust and recheck. Any manual drag, resize, or keyboard move after that immediately clears the old "after" comparison, so you're never looking at a stale result next to a placement you've since changed.

What "Safe" actually means

Safe means: for the platform reference regions currently loaded, the Subtitle's rectangle doesn't intersect them and clears a small margin. It is a geometry check against the evidence this tool has — not a guarantee that your caption will be visible in every install of every app, on every device, for every viewer. See the platform guides for what each platform's reference is actually based on, and FAQ for the most common follow-up questions.

Demo data vs. reference data

The Data selector above the preview switches between two very different things. MOCK / DEMO is synthetic geometry, useful for trying the tool without waiting on real evidence — it's labeled DEMO everywhere in the main interface for that reason. Reference · Organic switches to the platform evidence described in the guides — first-party phone captures for Reels and TikTok, and an independent secondary measurement for Shorts. Each preview's source details show where its reference came from. The two datasets are never averaged or mixed.