How to Resize a Video Online for Free in Your Browser

To resize a video, drop it onto the Resize Video tool, pick a resolution preset like 720p or enter a custom width, then click Resize video — the height is set automatically to keep the aspect ratio and you get a compatible MP4 to download. It runs entirely in your browser, so nothing is uploaded and there are no size limits or accounts.

This guide walks through each step, explains the presets, and shows how the in-browser engine works so you know what to expect. Scaling a video down is the simplest way to shrink a file, meet an upload limit, or match a platform's expected dimensions.

What resizing a video actually does

Resizing changes the resolution — the number of pixels in each frame. Going from 1080p to 720p, for example, reduces the frame from 1920 by 1080 down to 1280 by 720, which means far fewer pixels to encode and usually a much smaller file. The tool re-encodes with H.264 video and AAC audio into a standard MP4, so the result plays almost anywhere.

Step-by-step: resizing your video

1. Add your video — drag it onto the drop box or click to browse and select a file.
2. Choose a size — pick a preset (1080p, 720p, 480p or 360p) or select Custom width and type an exact value.
3. Click Resize video and let the in-browser engine work. A short clip finishes quickly; long or high-resolution files take longer because every frame is re-encoded on your own device.
4. Preview and download the resized MP4 once it is ready.

Choosing the right preset

Only the width is set from the preset or your custom value; the height is calculated automatically to preserve the original aspect ratio, so the picture never stretches or squashes.

Why it runs in your browser

The tool uses a WebAssembly build of ffmpeg, which means all processing happens locally on your machine. Your video is never uploaded to a server, there is no account to create, and once the page has loaded it works offline. That makes it ideal for private footage you would rather not send anywhere.

Try the Resize Video — free and 100% in your browser.

Frequently asked questions

What formats can I resize?

Common video files work as input, and the output is always a standard MP4 with H.264 and AAC for wide compatibility across phones, browsers and editors.

Will resizing lower the quality?

Scaling down reduces resolution, so a smaller frame naturally holds less detail. For most sharing and previews the trade is worth it, and the aspect ratio is always preserved so nothing looks distorted.

How do I hit an exact width a platform requires?

Choose the Custom width option and type the exact value. The height adjusts automatically to keep proportions, giving you the precise width without manual math.

Why does a long video take a while?

Because every frame is re-encoded using your own CPU rather than a server. Short clips are fast; long or high-resolution videos take longer, so a modern desktop browser is best for big files.

Related free tools

• Compress Video — shrink file size further after resizing.
• Trim Video — cut a clip to the part you need.
• Video Converter — change the file format.
• MP4 to GIF Converter — turn a clip into a GIF.

Built by ByteVancer

ByteTools is a free product of ByteVancer, a software and web development studio building web apps, SaaS and custom software. If private, browser-based media tools appeal to you, explore what ByteVancer can build for your team.