Resize MP4 for Free Online
Change the shape of an MP4 right in your browser for free. Pick vertical, square, horizontal, or portrait, and export it. There's nothing to install.
Over 1 million creators use Flixier every day including brands like:
How to Resize MP4 Videos
Resize an MP4 for Any Platform
Pick a Target Ratio
There are four ratios to choose from: 9:16 for vertical, 1:1 for square, 16:9 for horizontal, and 4:5 for portrait. Choose one in the video resizer and it works out the output resolution itself, so you don't need to know what numbers it has to be.
Crop or Letterbox It
Changing ratio means something has to give at the edges. Crop to fill trims away whatever sits outside the new frame, while Letterbox keeps the whole picture and pads it with bars. You can switch between the two and drag the crop box around until the right part of the shot is inside it.
Process It Locally
Some footage you just can't upload. Unreleased product shots, client work under NDA, anything with a face in it you haven't cleared yet. The resizer runs on your own computer, so none of that has to go near a server just to come out in a different shape.
Edit After Resizing
A resize doesn’t fix pacing or sound. Open the project in the full Flixier video editor to trim the opening, add captions, or enhance the audio, then export at the ratio you already set, so you don't run the resize twice.
Everything you need to create
and finish AI videos
Who This Is For
Marketers
Most ad sets need the same footage in three or four shapes before anything can run. Resizing a cut that's already been approved is faster than commissioning new versions, and it keeps the message identical wherever it's placed.
See How It WorksEducators
Business Owners
Social Creators
Still have questions?
We got you!
Can I resize an MP4 without losing quality?
The resizer exports at a set resolution for each ratio, so a vertical export comes out at 1080 by 1920 whatever you put in. How that looks depends on your source. Crop to fill also drops whatever sits outside the new frame. If it's a smaller file you're after, the MP4 compressor handles that.
Can I change the aspect ratio of an MP4?
Yes. Pick one and the output resolution follows automatically. The X, Y, W and H fields let you nudge the crop region in pixels when the default framing doesn't catch what you wanted.
What other video formats can I resize?
Alongside MP4, the resizer takes WebM, MOV, and MKV with no conversion step first, so whatever came off your camera or screen recorder goes straight in. If you'd rather start from a page built around your own format, there's a dedicated WebM resizer doing the same job.
