Resize Video Online

Make videos smaller or fit a target layout

Video dimensions matter when you are preparing a clip for a web page, learning platform, email, documentation page or social post. A 4K recording may be too large for a quick preview, while a wide screen recording might need a smaller width before it is embedded in an article. This tool resizes the picture to a target width and lets ffmpeg calculate the matching height so the image does not stretch.

Everything stays in your browser. The selected video is copied into the ffmpeg.wasm engine only after you press the button, processed in memory and returned as a local download. No upload, account or remote worker is involved. That makes it practical for private drafts, unpublished lessons, bug recordings and internal demos that you do not want to send to a conversion service.

Choosing a useful width

The presets provide quick targets for common web-friendly sizes: 1080 pixels for larger previews, 720 pixels for a balanced default and 480 pixels for compact clips. You can also choose custom and enter any positive width. The scale filter uses an automatic even height, which helps video encoders create compatible output while preserving the original aspect ratio.

Quality and runtime expectations

Resizing requires re-encoding the video, so it takes longer than a simple file copy. Runtime depends on the original resolution, duration and your device. The first resize may pause while the WebAssembly media engine downloads, then subsequent runs in the same tab can start faster. Always preview the downloaded MP4 before deleting the original, especially when resizing text-heavy screen recordings where small details can become harder to read.

Examples and details

A 3840×2160 clip resized to a width of 1280 becomes 1280×720, because the height is computed to keep the 16:9 shape. A vertical 1080×1920 phone video resized to 720 becomes 720×1280. The value you enter is always the width, so for vertical footage pick the width of the final vertical frame, not the long side. Custom widths should be even numbers; the field steps in twos for that reason.

The scale filter can also enlarge a video, but upscaling only adds pixels and never adds detail, so the picture looks softer and the file grows. Use resizing mainly to go smaller. Output is H.264 at CRF 23 with AAC audio at 160 kbps in an MP4 container, which plays in nearly every browser and phone. If you care mostly about file size instead of exact dimensions, the video compressor gives you a CRF control as well.