RunToolRunVideo Resolution Changer
Change video resolution.
How to Change Video Resolution
Select a video
Click the upload area or drop an MP4, MOV or WebM file.
Pick the target resolution
Choose 1080p, 720p, 480p — or vertical 9:16 and square 1:1 presets for social media.
Download the resized video
Save the re-encoded MP4 at the new resolution, processed in your browser.
Downscaling works, upscaling does not
Reducing resolution combines several source pixels into each output pixel. Information is discarded deliberately and the result looks correct — a well-made 720p version of a 1080p file is genuinely sharp.
Increasing resolution has nothing to draw on. The extra pixels are interpolated from neighbours, so the output is larger and softer, never more detailed. A 720p file scaled to 4K is a blurry 4K file, and it is also four times the size for no benefit.
Resolution and bitrate together
Halving both dimensions removes three-quarters of the pixels, and the file shrinks accordingly — but only if the bitrate is allowed to fall with it. Keeping a 1080p bitrate on a 720p encode wastes space without improving anything visible.
Conversely, dropping resolution while keeping the bitrate very low produces a small, soft, blocky file. The two settings work together, and adjusting one without the other is where disappointing results come from.
Choosing a target
Match the destination. A video embedded in a slide or a page at a few hundred pixels wide gains nothing from 4K. Video for a phone feed rarely benefits above 1080p. Archival footage should stay at its native resolution.
The common mistake is treating the highest number as the best choice. Higher resolution costs upload time, storage, playback battery and — on a slow connection — the viewer's patience.
Frame rate is a separate decision
Resolution and frame rate are independent, and lowering frame rate is a legitimate way to reduce size for content that does not need smoothness — a talking head, a screen recording of static content.
Converting between frame rates is where it gets awkward. Going from 30 to 24 frames per second means dropping frames, which produces visible judder in panning shots. Where the source frame rate suits the content, leaving it alone is usually right.
Aspect ratio must be preserved
Changing width and height independently stretches the picture, and viewers notice immediately on faces even when they cannot name what is wrong. Standard resolutions share the same 16:9 shape, which is why moving between them is safe.
Changing the shape of the frame is a cropping operation rather than a resolution one, and treating it as a resolution setting is how videos end up subtly squashed.
Encoding locally
Re-encoding runs through FFmpeg compiled to WebAssembly in your browser. Nothing is uploaded, which matters for personal and confidential footage, and it is single-threaded, so a long high-resolution file is a genuine wait.
Downscaling is faster than upscaling and produces a better result. If you are unsure, downscaling from the highest-quality original you have is almost always the right move.