Video Resize Tool

Upload a video, type the exact width and height you need (or lock the aspect ratio so one follows the other), pick how the frame should fit the new dimensions, and export a resized MP4 or WebM with the original audio intact. Useful for matching a platform's required resolution, shrinking a file for upload limits, or standardizing dimensions across a batch of clips. Everything happens on-device via the browser's native WebCodecs API, no upload to a server involved.

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Reviewed by Vincenzo Manto, Founder & Lead Developer · Last updated October 11, 2026

How it works

  1. 1

    Upload a video file and let it load in the player.

  2. 2

    Enter the target width and height, or lock the aspect ratio to keep proportions.

  3. 3

    Choose a fit mode: fill, contain, or cover.

  4. 4

    Pick MP4 or WebM and export. The tool re-encodes the file at the new size with its original audio.

Pixel-exact resizing, no plugins or uploads needed

Rather than relying on a heavyweight WebAssembly build of FFmpeg, this tool uses the browser's own native WebCodecs API to read, resize, and re-encode your video directly, including its audio track, producing a real MP4 or WebM file at precisely the dimensions you set without ever sending your video to a server.

Aspect-ratio lock keeps proportions sane

Toggling the aspect-ratio lock recomputes the other dimension automatically whenever you change width or height, based on the loaded video's natural proportions, so you can target a specific width (say, for a web embed) without manually working out the matching height.

Frequently asked questions

Will resizing distort my video?

Only if you pick 'fill' with dimensions that don't match the source aspect ratio, or disable the aspect-ratio lock while setting a mismatched size. Use 'contain' to letterbox without distortion, or 'cover' to crop and fill without stretching.

What's the difference between fill, contain, and cover?

Fill stretches the frame to exactly match your width and height, possibly distorting it. Contain scales the video to fit inside the box, adding letterbox bars if the aspect ratios differ. Cover scales the video to fill the box completely, cropping any excess.

Does the resize happen on a server?

No. Reading the file, resizing, and re-encoding all happen entirely client-side in your browser tab using WebCodecs, so the video is never uploaded anywhere.

Will the exported video have audio?

Yes. The original audio track is preserved and re-encoded alongside the video (as AAC for MP4 or Opus for WebM).

Can I upscale a small video to a larger resolution?

Yes, you can type any width and height larger than the source. Keep in mind upscaling can't add detail that wasn't in the original, so very small source videos will look soft at large target sizes.

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