Why videos end up sideways — and how rotation works
Phones always record in the sensor’s orientation and add a rotation flag (display matrix) that tells players how to turn the picture. If the phone guessed wrong — for example when you started filming flat on a table — the video appears sideways or upside down.
For MP4 and MOV, the lossless mode simply writes a new rotation flag. The video data is copied unchanged, so it takes seconds and there is no quality loss. All modern phones, browsers, VLC, QuickTime and social networks respect the flag.
Some older TVs, video editors and players ignore the flag. For them choose Re-encode: every frame is rotated and encoded again, so the picture is upright no matter where it plays. WebM and MKV files are always re-encoded because these formats have no rotation flag.
Which rotation do I need?
| Your video looks… | Choose | Result |
|---|---|---|
| Turned to the left (top is on the left) | Rotate right (90°) | Upright |
| Turned to the right (top is on the right) | Rotate left (270°) | Upright |
| Upside down | 180° | Upright |
| Mirrored (text reads backwards) | Mirror | Correct side |
| Correct on the phone, sideways elsewhere | Re-encode with no extra rotation | Upright everywhere |
Tips
- Check a file’s rotation flag with the Video Metadata Viewer.
- After rotating, crop away black bars with the Video Cropper.
- Turning a landscape video into a vertical one for TikTok? Use the TikTok / Reels / Shorts Converter.
- If a video plays correctly on your phone but sideways on a TV, use Re-encode.