Rotate Video

Why videos end up sideways

A phone's camera sensor is always landscape. When you film holding the phone upright, most phones still record landscape frames and add a rotation instruction to the file — a display matrix in MP4 and MOV — telling the player to turn the picture by 90° when showing it. The video is not stored portrait; it is stored landscape with a note.

Most modern players read that note. But some do not: older Windows players, some smart TVs and set-top boxes, some editing applications, and occasionally the processing pipeline of a website you upload to. They show the raw landscape frames, and your portrait clip appears on its side.

The other cause is the phone guessing orientation wrong — filming while lying down, or pointing straight down at a table — so the rotation note itself is wrong, and even players that obey it get it wrong.

Rotating the pixels, not the flag

There are two ways to rotate a video. One changes only the rotation note, which is instant and lossless — but the result looks right only in players that honour the note, and the players that ignore it are usually the reason you are here. Desktop ffmpeg can do that with a stream copy, if it is what you need.

This tool does the other: it turns the actual pixels. ffmpeg decodes each frame, rotates it with the transpose filter (or flips it with hflip or vflip), and encodes a new H.264 MP4 with no rotation note at all. A 1920×1080 frame becomes a genuine 1080×1920 one, upright in every player, editor and upload pipeline, because there is nothing left for any of them to misread.

Any rotation note already in the file is applied first. The rotation you choose is therefore relative to how the video plays now in your browser — what you see in the preview is what you get.

Which option to choose

90° clockwise or counter-clockwise: the video is lying on its side. Look at the preview and choose the direction that brings the top of the scene to the top.

180°: the video is upside down — typically from a phone held the wrong way up, or a camera mounted inverted on a bike or a ceiling.

Flip horizontally: mirror the picture left to right. Front-facing cameras often save a mirrored image, so text on a T-shirt or a sign reads backwards; flipping fixes it. Flip vertically turns the picture over top to bottom without mirroring sideways, which is occasionally needed for footage from scanners, microscopes or mirrors.

Cost: time and a re-encode

Because every frame is decoded and encoded again, rotating takes as long as compressing the video — single-threaded in the browser, roughly eight minutes per minute of 1080p at the default setting on a recent desktop, three to four for 720p, and about a third of that with Fastest.

A re-encode also costs a little quality. At the default CRF 23 it is hard to see; choose Higher quality (CRF 20) if the video will be edited further. The audio is copied untouched when it is AAC or MP3, and converted to AAC otherwise.

If you also need the video shorter or smaller, combine jobs to avoid encoding twice: trim it first in the Video Trimmer's fast mode, which copies without re-encoding, then rotate the shorter clip here.

Rotating on the phone first

If the video is still on your phone, its photo app can usually rotate it. On an iPhone, open the video in Photos, tap Edit, choose the crop tool and tap the rotate button until it is upright. In Google Photos on Android, open Edit, then Crop, and use Rotate. Menus differ between versions, but the crop view is where rotation lives in both.

Those apps also save a re-encoded copy, so the result behaves like the one made here. This page is for videos already on a computer, for formats a phone app will not open — MKV, AVI, WebM — and for clips whose rotation flag a particular player or site keeps getting wrong.

Your video stays here

The rotation runs in ffmpeg compiled to WebAssembly, inside this browser tab. Nothing is uploaded; the only download is the engine itself, about 32 MB, on first use.