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Resize video

Shrink a video to fit a target resolution or an exact size. Everything runs in your browser; your file never leaves your device.

How Resize video works

Video resize changes the pixel dimensions of a clip using ffmpeg's scale filter, entirely inside your browser. Pick a resolution preset (1080p, 720p or 480p, source aspect ratio preserved), a percentage of the source size, or an exact custom width and height, and ffmpeg re-encodes the video stream at the new size while copying the audio untouched.

Every mode is even-dimension safe: the standard yuv420p pixel format that most players expect requires width and height divisible by two, so preset and percentage mode use ffmpeg's own even-rounding (the -2 scale value), and custom mode rounds an odd input down to the nearest even number rather than failing the encode.

Written by Bastien Sulyan

How to use Resize video, step by step

  1. Drop or select the video you want to resize.
  2. Choose a mode: a resolution preset, a percentage of the source size, or a custom exact width and height.
  3. Pick the target value (e.g. 720p, 50%, or 640x360).
  4. Click Start and let ffmpeg re-encode the video at the new size on your device.
  5. Download the resized file once processing finishes.

Common use cases

  • Shrinking a 4K phone recording to 1080p or 720p before sharing it to save bandwidth.
  • Reducing a video to a small custom size to embed as a lightweight background loop on a web page.
  • Matching a batch of clips to the same resolution before merging them elsewhere.
  • Cutting a large recording down to a percentage of its size to fit an upload limit.

Frequently asked questions

Is my video uploaded anywhere to resize it?

No. ffmpeg compiled to WebAssembly runs the scale filter inside your browser tab. The file is read into memory on your device, resized there, and the result is offered as a local download. Open your browser DevTools Network tab while running the tool: no request carries your video.

Does resizing preserve the aspect ratio?

In preset and percentage mode, yes: only one dimension is set directly (the target height for a preset, the target width for a percentage) and the other is derived to keep the source proportions. In custom mode you set both width and height yourself, so an aspect ratio that does not match the source will stretch or squeeze the image; that trade-off is stated in the tool.

Why does resizing require odd dimensions to be rounded to even numbers?

The yuv420p pixel format used by the H.264/VP8 encoders this site relies on samples chroma at half resolution in both directions, which only works cleanly on even width and height. An odd value would fail the encode outright, so the tool rounds it down to the nearest even number automatically rather than erroring.

Does resizing change the video quality?

Downscaling (making the video smaller) generally looks clean since detail is being discarded, not invented. Upscaling (making it larger) does not add real detail, it only stretches existing pixels, so a video enlarged well beyond its source resolution will look soft rather than sharper.

What is the largest file I can resize?

Up to 500 MB, the same ceiling as the other one-shot ffmpeg video tools on this site. A memory-constrained mobile device gets a lower limit automatically to protect the browser tab.

Does video resize work offline?

Mostly, yes. The resize itself always runs on your device, so your video never leaves your machine. The one caveat: ffmpeg's engine is a sizeable download fetched from this site the first time you use any ffmpeg-based tool. Once that download and the page have both completed, you can disconnect from the network and resizing still works.