What is video resolution?

A video's resolution is its size in pixels, such as 1920 × 1080 for Full HD or 1280 × 720 for HD. Resolutions are often named by the short side, so 1080p means 1080 pixels tall for a landscape video. Lowering the resolution makes the file smaller and easier to send, upload, or play on slow devices, while raising it makes a small video fit a larger frame, although it can't add detail that wasn't there.

Tool description

This tool resizes a video in your browser. Pick a standard size from 240p to 2160p (4K), or enter your own width and height, and download the resized video as an MP4. The menu shows the exact size each preset gives your video, and the original and new sizes are shown side by side. Nothing is uploaded: the video is processed on your device with FFmpeg compiled to WebAssembly.

Features

  • Presets for 2160p, 1440p, 1080p, 720p, 480p, 360p, and 240p
  • Presets apply to the short side, so portrait phone videos get the right size too
  • Custom width and height, with the other side filled in from the aspect ratio when you leave it empty
  • Exact sizes when you enter both, for example a square 1080 × 1080 video
  • Saves as MP4 with H.264 video and AAC audio, which plays almost everywhere
  • Shows the output file size and a preview before you download

How it works

The tool reads the video's size in the browser and works out the new size, rounding each side to an even number because H.264 needs even dimensions. FFmpeg then scales every frame with the Lanczos filter, which keeps edges sharp, and encodes the video again. When you enter both a width and a height that don't match the original shape, the picture is stretched to fill the new size.

Tips

  • To make a video smaller for sharing, 720p is usually a good balance between file size and quality.
  • To change the shape of a video without stretching it, crop it instead of entering both a width and a height.
  • Re-encoding in the browser is slower than in a desktop app, so long or high-resolution videos can take several minutes.
  • The first run downloads FFmpeg, about 30 MB. Later runs on the same page start right away.