Why this aspect ratio converter is fast on Clipy
Reframing means scale + crop + re-encode — the encode is the expensive part. Browser-wasm ffmpeg runs it in a single CPU thread inside a browser tab, which is why competing free tools take minutes for any clip longer than a few seconds. We run native ffmpeg on dedicated workers, where the H.264 encoder can use every available core. The upload leg goes straight to the nearest Backblaze B2 POP via a presigned URL, and the finished MP4 ships through Bunny CDN. No browser memory ceiling, no shared queue, no transatlantic upload — just a clean reframe in seconds.
What this tool does, exactly
Pick a target ratio from the toggle and the encoder behind it runs the right ffmpeg filter chain. Crop uses scale + crop to fill the new frame edge-to-edge, trimming whatever spills past the target rectangle. Fit uses scale + pad to keep every source pixel and add black bars to make up the difference. Output is always H.264 (CRF 22, visually transparent) + AAC 160 kbps inside an MP4 with +faststart and yuv420p pixel format — the combination that autoplays on every modern platform. Default output sizes are 1080×1920 (9:16), 1080×1080 (1:1), 1080×1350 (4:5), and 1920×1080 (16:9).
Crop vs letterbox vs scale — when to pick each
There are only two honest ways to put a 16:9 clip into a 9:16 frame, and pure scale (squashing) isn't one of them — that just distorts faces and text. Crop (scale-to-fill) is right when your subject is centered, like a person on camera or a UI element in the middle of the screen. It looks native on TikTok and Reels because the algorithm rewards full-frame vertical content. Letterbox (fit-with-bars) is right when nothing in the frame can be sacrificed — a slide, a dashboard, a chart with axis labels at the edges. The bars hurt engagement on vertical feeds but are safer when the alternative is cropping out information. Scale (stretch-to-fit) is wrong for video almost always; don't use it unless the source aspect was already correct and you just need a different resolution.
Sister tools
For pixel-level dimension control rather than ratio presets, use resize video. For trimming the frame down to a specific region first, crop video. If you also need to fix orientation, rotate video. Reframed output is bigger than you want? Video compressor. Stitching multiple reframed clips into one? Merge videos.
Record vertical in the first place
Reframing is always a compromise — you're either throwing away pixels (Crop) or adding empty space (Fit). The cleanest vertical clip is one that was framed vertical from the start. If you make a lot of short demos for social, Clipy lets you record a region or a window so your subject is already composed for 9:16 — then you skip the crop guesswork entirely.