Why this rotate video tool is fast on Clipy
The honest fix for a sideways video is to bake the rotation into the actual pixel grid — and that means re-encoding. Browser-wasm rotate tools spend most of their wall-clock time on the H.264 encode in a single CPU thread, which is why a 30-minute screen recording can take 10+ minutes to rotate in a browser tab. We run native ffmpeg on dedicated workers. The encoder uses every available core, and the upload + download legs ride your nearest Backblaze B2 POP via presigned URL — closest edge in and Bunny CDN out. A long iPhone clip that would crash a browser-side tool just finishes here.
What this tool does, exactly
Output is an MP4 with H.264 video (CRF 22, visually transparent) and the original audio track copied byte-for-byte. A 90° rotation swaps width and height — a 1920×1080 source becomes 1080×1920, which is the point if you wanted a vertical clip and got a sideways one. Flips don't change dimensions at all. The rotation is written into pixels via the transpose filter (90° CW = transpose=1, 90° CCW = transpose=2) so every player gets it right — including the ones that ignore the source's rotation metadata atom. Audio uses -c:a copy so the audio bytes are unchanged.
Why phone videos play sideways in the first place
Phones record sensor data the same way regardless of how you're holding them, then write a rotation flag into the file metadata describing which way is up. Most modern players read that flag and rotate on the fly — but plenty of them don't. PowerPoint embeds, older Windows Media Player, some Slack previews, corporate VPN-routed video tools, half the embedded players on niche CMSes. The fix is to bake the rotation into the actual pixel grid so every player renders it correctly regardless of whether it respects the metadata flag. That's what this tool does — and why running a file through it makes "sideways on Windows" bug reports go away.
Sister tools
Rotated output is often the start of a pipeline. Need to drop a webcam corner that ended up in the new orientation? Crop video cuts the frame down. Going to ship it as an autoplay-muted social embed? Mute video strips the audio as a stream-copy. Joining several rotated clips? Merge videos handles the concatenation. Need a specific aspect ratio after rotating? Resize video. Output too big? Video compressor. Recording fresh? Clipy lets you pick orientation at capture so you never have to come back here.
After rotating, double-check the aspect ratio
Rotating 90° swaps width and height — a 1920×1080 source becomes a 1080×1920 output. That's probably what you want (you wanted a vertical video, not a sideways one), but if your destination needs a specific shape, run the result through the aspect ratio converter afterwards. Flipping doesn't change dimensions at all, so flip-then-upload is usually the whole pipeline.