Video Resizer

Change the resolution of a video: shrink a 4K phone clip to 1080p or 720p so it is smaller and easier to share, make a square or vertical version at an exact size for a website or app, or scale an old low-resolution clip up to 720p for an editing project. Presets work on the short side, so portrait videos stay portrait. The result is an H.264 + AAC MP4 made in your browser with the ffmpeg engine (about 30 MB, downloaded the first time); your videos are never uploaded.

How to use this tool

1. Pick a preset (2160p to 240p), a percentage, or an exact width × height.
2. For exact sizes, choose bars, crop, fit without bars or stretch, and the bar colour.
3. Choose one or more videos; resizing starts right away.
4. Compare the old and new resolution and file size, then download.

Formula

Preset p: short side = p, long side = p × long ÷ short (rounded to an even number)

Sizes use the picture as players show it: rotation is applied and non-square pixels are corrected, so the result has square pixels. H.264 needs even widths and heights, so every size is rounded to the nearest even number. "Fit inside with bars" scales the whole picture into the box and fills the rest with the bar colour; "Fill and crop" scales until the box is covered and trims the overflow evenly. Scaling uses the bicubic filter; AAC and MP3 sound is copied unchanged.

Example

A 3840 × 2160 clip at 720p becomes 720 × 3840 ÷ 2160 = 1280 × 720: a third of the width and height, so one ninth of the pixels, and a much smaller file. A 1080 × 1920 vertical video fitted into 1080 × 1080 with bars is scaled to 608 × 1080 and centred between two 236-pixel bars.