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Whether you need a lighter 720p copy of a 4K clip or an exact 1080×1920 file for a vertical feed, this tool rescales the picture and saves a fresh MP4. A live preview shows the new framing before anything is encoded.
Processing locally on your device
Overview
Resolution is the number of pixels in each frame, and it drives file size more than anything else. A 4K frame (3840×2160) holds four times as many pixels as 1080p and nine times as many as 720p, so downscaling is one of the most effective ways to make a video lighter while it still looks sharp on a phone or laptop. The Resolution tab offers 2160p, 1440p, 1080p, 720p, 480p and 360p. Each preset sets the shorter side and keeps the aspect ratio, so a vertical 1080p video becomes 1080×1920 rather than being squeezed into a landscape frame.
Custom size lets you type an exact width and height between 16 and 7680 pixels. With the link icon on, changing one value updates the other to keep the original proportions. Social shortcuts fill in 1080×1920 (9:16), 1080×1080 (1:1) and 1280×720 (16:9). When the new shape differs from the source, you choose how to handle it: Fit shows the whole frame and adds bars in black, white or any colour you pick; Fill covers the frame and crops what overflows; Stretch squeezes the picture to the new shape, which distorts it. The preview updates instantly, and the tool warns you if the settings would enlarge the video, since upscaling can't add detail.
Scaling uses FFmpeg's Lanczos filter, which keeps edges and text crisp, and dimensions are rounded to even numbers as H.264 requires. The video is re-encoded to H.264 MP4. A quality slider sets the CRF value from 16 to 34, with 23 as the default: lower numbers keep more detail and make bigger files, higher numbers make smaller files. Audio from MP4, MOV, M4V and 3GP files is copied unchanged; audio from WebM, MKV and other containers is converted to AAC so the MP4 plays everywhere.
FFmpeg 5.1 runs inside your browser as WebAssembly. It downloads once (about 31 MB) and is cached, and your video is read from disk instead of being uploaded. Re-encoding is CPU-bound: downscaling a few minutes of 1080p to 720p usually runs around real time on a modern laptop, while large 4K sources take longer.
| Preset | Landscape | Vertical | Typical use |
|---|---|---|---|
| 2160p (4K) | 3840×2160 | 2160×3840 | Large TVs, archiving |
| 1080p | 1920×1080 | 1080×1920 | YouTube, Reels, most sharing |
| 720p | 1280×720 | 720×1280 | Messaging, email, web embeds |
| 480p | 854×480 | 480×854 | Slow connections, older devices |
| 360p | 640×360 | 360×640 | Previews, very small files |
Drop a video into the resizer.
Pick a resolution preset, or switch to Custom size and enter a width and height.
For custom shapes, choose Fit, Fill or Stretch, and a bar colour for Fit.
Adjust the quality slider if you want a smaller or sharper file.
Click Resize, check the result and download the MP4.
Use cases
Phones record 4K by default, which makes huge files. A 1080p or 720p copy is a fraction of the size and still looks clean on the small screens most people watch on.
Turn a landscape clip into a 1080×1920 or 1080×1080 video. Fit keeps the whole frame with bars, while Fill crops to the centre for a full-screen look.
Course platforms, ad managers and kiosks often want an exact size such as 1280×720. Type the numbers and the output matches exactly.
A 480p or 360p version streams smoothly over weak mobile data and plays on older tablets and TVs that struggle with high resolutions.
Pro tips
Answers to common questions about the video resizer.
Not with the resolution presets, which set the shorter side and scale the other to match. In Custom size, keep the link icon on to preserve proportions, or choose Fit or Fill to control what happens when the shape changes.
CRF sets H.264 quality. Around 18 is close to visually lossless, 23 is a balanced default, and values near 30 give small files with visible softening. Lower numbers mean bigger files.
Yes, up to 7680 pixels per side, but enlarging can't create detail that wasn't recorded. The tool shows a warning with the enlargement factor so you know when that's happening.
Audio from MP4, MOV, M4V and 3GP sources is copied as it is. For WebM, MKV and other sources it is converted to AAC at 160 kbps so the resulting MP4 plays on every device.
It depends on the length, the source resolution and your computer, because every frame is decoded and encoded again in the browser. Short phone clips take seconds; long 4K videos can take many minutes.
No. ToolEnhancer processes files on your own device inside the browser. They are never sent to, stored on or seen by our servers.
Yes. The video resizer is free to use with no sign-up, no watermarks and no daily limits.