Most caption problems aren’t in the text. They’re in how the text sits on screen — and that’s precisely the part almost nobody checks before delivery.
A TTML, WebVTT, SCC, or STL file is just a set of instructions: this text, at this time, positioned here, styled like this. Whether it renders the way you intended depends on how the player interprets those instructions — and different destinations interpret them differently. A caption positioned fine in one player might overlap a lower-third graphic in another. Styling that looks correct in your authoring tool might render with the wrong font weight, wrong background opacity, or wrong safe-area positioning somewhere else in the chain.
The only way to actually know is to look at it rendered — not read the raw file, not trust the authoring software’s preview pane, but scrub through the real timing and positioning the way a viewer would see it.
What the Timed Text Renderer does
Load a TTML, WebVTT, SCC, or STL file and scrub through a live, composited preview of exactly how the captions will render — positioning, styling, and timing all together. You can composite over a plain checkerboard or solid colour to isolate the caption styling itself, or load the actual video underneath to see it in context — which is where you catch the problems that actually matter, like a caption sitting directly over a burned-in graphic or dropping off the edge of the safe area on a particular aspect ratio.
Why this catches things a text-only review never will
Reading a caption file tells you the words are right. It tells you nothing about whether line 340 renders three lines high and clips off the bottom of frame, or whether a speaker change happens half a second before the audio actually changes speaker. Those are exactly the kind of issues that get flagged in QC — and exactly the kind that are far cheaper to catch yourself first.
This tool is built for that first-pass visual check. Full compliance QC — accessibility standards, reading speed limits, regional formatting rules — is a deeper pass, and it’s the kind of thing we run as part of QC & Compliance for anything going to a specific platform or broadcast spec. But for “does this actually look right,” this gets you there in a couple of minutes, entirely locally.
All FooEngine tools run locally in your browser. No files are uploaded to any server.