# Rotate Video > Fix a sideways video: rotate it 90°, 180° or 270° in your browser — no upload, no re-encoding. Only the orientation flag changes, so quality is identical. - URL: https://bytescope.dev/en/rotate-video/ - Locale: en · Also: [ja](https://bytescope.dev/ja/rotate-video.md) · [zh-Hant](https://bytescope.dev/zh-Hant/rotate-video.md) - Runs: Your files never leave your browser — all processing is local. - Requires: Any modern browser can rotate. Saving straight into a file you choose needs Chrome, Edge or Opera on desktop (File System Access API). Other browsers build the output in memory and stop around 1 GB. - Updated: 2026-09-08 ## What it does Drop an MP4, MOV, WebM or MKV file, press "Rotate left", "Rotate right" or "180°" until the preview looks right, and export. The whole thing takes a few seconds even for a long video, because nothing is decoded: the picture and sound inside the file are copied exactly as they are, and only the orientation flag in the container is rewritten. The file never leaves your computer. This is the fix for the phone video that plays sideways on a computer or TV, or the clip you shot holding the phone upside down. ### What the orientation flag is A phone does not turn the picture when you hold it sideways. The sensor records the frames the way it sees them, and the file carries a small note — "display this turned 90°" — that every player reads before drawing a frame. That is why a clip can look fine on the phone and sideways somewhere else: one player read the note, the other did not. This tool reads the note your file already has, adds the turn you chose, and writes the result back. Choosing 90° on a clip that already says 90° gives 180°, so the preview always shows what the final file will say. After exporting, the page reads the new file again and refuses to hand it over if the flag does not match what you asked for. ### Why WebM and MKV come out as MP4 MP4 and MOV have an orientation field that players have agreed on for years, so those files stay in their own container. WebM and MKV have no such field that players consistently honour, so a rotated WebM or MKV is written as an MP4 instead — the packets are still untouched, only the box around them changes. For now this only works when the video is H.264, HEVC, VP9 or AV1 and the audio is AAC, Opus, MP3 or FLAC. VP8 video and Vorbis or PCM audio can technically be put in an MP4, but many players do not expect them there, so the tool stops and names the codec instead of producing a file that might not play. ### Honest limits Because only the flag changes, the result depends on the player honouring it. Most players and phones do; some players, older TVs and some website upload pipelines may ignore it and still show the video sideways — we have not tested which. Actually rotating the pixels would need re-encoding, and this page never re-encodes. Rotation is limited to multiples of 90°: no free angles, no mirror or flip. One video per run. If the preview stays black, your browser cannot decode that codec (often HEVC on a computer without an HEVC decoder) — the rotation still works and the result plays wherever the original did. On desktop Chromium the output streams straight into a file you choose, so a large video never sits in memory; other browsers build it in memory with a limit of about 1 GB. The output is a fresh container that carries only the video and audio packets, not the source's descriptive tags such as title, date or GPS location. If you also want to cut the clip, Video Trimmer does the same copy with an in and out point; Mute Video drops the sound; Video Info shows what a file says about itself, including its current orientation. ## Limits Does not re-encode or turn the pixels, rotate by free angles, mirror, trim or compress; it rewrites the orientation flag. WebM and MKV come out as MP4. ## FAQ ### Does rotating reduce the video quality? No. The frames are not decoded or re-encoded — the compressed video and audio packets are copied bit for bit into a new file, and only the orientation flag in the container is different. Resolution, bitrate and codec are exactly what they were. ### Why does my rotated video still play sideways in some player? Because this tool changes the orientation flag, not the pixels, and that player is ignoring the flag. Most current players, browsers and phones honour it; some players, older TVs and some upload pipelines on websites do not, and we have not tested which. If you need a file that is right side up even for those, the pixels have to be re-encoded, which this page deliberately does not do. ### Why did my WebM file come out as MP4? WebM and MKV have no orientation flag that players reliably honour, while MP4 does. So the tool keeps your video and audio packets exactly as they are and writes them into an MP4 container, where the flag will be read. This works for H.264, HEVC, VP9 and AV1 video with AAC, Opus, MP3 or FLAC audio. VP8 video or Vorbis or PCM audio are refused for now, because many players do not expect them inside an MP4. ### Can I rotate by an angle other than 90°, or mirror the video? No. The orientation flag only knows four positions — 0°, 90°, 180° and 270° — and this tool only writes that flag. An arbitrary angle or a horizontal or vertical flip means changing every pixel, which requires re-encoding. ### Can I rotate iPhone or Android videos? Yes. Phone videos are the typical case: the file usually already carries an orientation of 90° or 270°, and the tool combines your turn with that value so the preview and the result agree. If your computer cannot decode HEVC the preview may stay black, but the rotation does not need to decode anything and the result plays wherever the original did. ### Is my video uploaded? No. The file is read from your disk in your browser and the result is written back to your disk; there is no server in between. That is also why there is no queue and no size limit on what you can open. ### How does this tool know the result is correct? After exporting, it opens the new file and reads the orientation back. If the value is not the one you asked for, the page tells you and does not offer the file for download — or, when it was streamed straight to disk, tells you to delete it. A wrong flag is never handed over silently.