Video resizer: resize video to the exact size you need
This video resizer changes the width and height of MP4, MOV, WebM and MKV videos right in your browser. Type exact pixels with the aspect ratio locked, scale by a percentage, or pick a ready-made size such as 1080p, 720p, a 1080 × 1920 vertical frame or a 1080 × 1080 square. A live preview shows one frame of the result before anything is encoded.
When the new size has a different shape from your clip, you decide what happens: fit the whole picture with colour bars, fit it over a blurred copy of itself, crop to fill the frame and drag to choose the part that stays, or stretch it. The file is decoded and re-encoded on your own device by the browser’s WebCodecs encoders, driven by the open-source Mediabunny library (MPL-2.0), so the video is never uploaded.
How to use the Video Resizer
- Drop a video on the upload area or click it to choose one. The panel shows its resolution, duration, codecs and file size.
- Choose Exact pixels and type a width (the height follows while “Lock aspect ratio” is ticked), Percentage to scale both sides, or Presets for standard sizes.
- If the new shape differs, pick Fit · colour bars, Fit · blurred fill, Crop to fill or Stretch. In crop mode, drag the preview to frame your subject; move the “Preview frame at” slider to check other moments.
- Under “Save as” keep MP4 · H.264 for the widest compatibility, set the quality and decide whether to keep the sound.
- Press “Resize video”, watch the progress bar (you can cancel at any time), then compare Before and After and press Download.
Video Resizer features
Three ways to set the size
Exact pixels with an aspect-ratio lock, a percentage, or presets from 360p to 4K plus vertical, square and 4:5 portrait frames.
Four fit modes
Colour bars in any colour, a blurred fill, crop to fill with a draggable focus point, or a plain stretch when you really want one.
Live frame preview
See the composed output frame before encoding and scrub through the clip to check that nothing important is cut off.
Even sizes handled for you
H.264 and most codecs need even widths and heights, so odd numbers are rounded and a badge shows the final size.
Choice of codec
Save MP4 with H.264, HEVC or AV1, WebM with VP9, or MOV — whatever your browser can encode is offered.
Private by design
Decoding and encoding run locally; you can cancel part-way and nothing is ever sent to a server.
Choosing a size: common video dimensions
Most video sizes come from a handful of standards. Pick the row that matches where the video is going; if your clip has a different shape, the fit mode decides how it is framed.
| Name | Pixels | Shape | Typical use |
|---|---|---|---|
| 2160p (4K UHD) | 3840 × 2160 | 16:9 | Large TVs, high-quality uploads |
| 1080p (Full HD) | 1920 × 1080 | 16:9 | YouTube, presentations, most screens |
| 720p (HD) | 1280 × 720 | 16:9 | Email-friendly clips, websites, older phones |
| 480p | 854 × 480 | 16:9 | Small previews, slow connections |
| Vertical 1080p | 1080 × 1920 | 9:16 | Reels, Shorts, TikTok, Stories |
| Portrait feed | 1080 × 1350 | 4:5 | Instagram and Facebook feed posts |
| Square | 1080 × 1080 | 1:1 | Feed posts, ads, profile videos |
Fit, crop or stretch — what each mode does
- Fit · colour bars scales the whole picture until it touches the frame edges and fills the rest with a solid colour. Nothing is lost; black bars give the classic letterbox (top and bottom) or pillarbox (left and right) look.
- Fit · blurred fill does the same but fills the empty space with a blurred, slightly darkened, zoomed-in copy of the video, so a vertical clip in a landscape frame looks intentional rather than boxed in.
- Crop to fill scales the picture until the frame is completely covered and trims what sticks out. Drag the preview to keep the important part — for exact cuts in pixels use Crop Video.
- Stretch forces the picture into the new shape. People and circles look squashed, so use it only to undo footage that was already distorted.
Will resizing make my video file smaller?
Usually, yes. Fewer pixels need fewer bits, and the quality setting chooses a bitrate that suits the new frame size, so a 4K phone clip resized to 1280 × 720 typically shrinks a lot. A video that was already heavily compressed can still come out larger, because it is re-encoded at a healthy quality rather than squeezed further. If you need a standard resolution rather than custom pixels, the video resolution converter picks the numbers for you.
Making a video bigger than the original never adds detail. The encoder has to invent the new pixels by blending existing ones, so a 480p clip blown up to 1080p looks soft — enlarge only when a platform insists on a minimum size.
Video Resizer FAQ
How do I resize a video without losing quality?
Keep the aspect ratio locked, choose “High” or “Very high” quality and avoid making the video larger than the original. Every re-encode loses a tiny amount of detail, but at high quality the difference is not visible in normal viewing.
Can I resize a video to 1080 × 1920 for Reels or TikTok?
Yes. Choose Presets → Vertical 9:16 · 1080 × 1920. For a landscape clip, “Fit · blurred fill” keeps the whole picture, while “Crop to fill” fills the screen and lets you drag the crop onto the subject.
Why did my width change by one pixel?
H.264 and most other codecs store colour at half resolution, so widths and heights must be even numbers. The video resizer rounds odd values to the nearest even number and shows the final size in the badge above “Save as”.
Is my video uploaded to a server?
No. The video is read, decoded, resized and encoded inside your browser tab using WebCodecs and the Mediabunny library.
Which video formats can I resize?
MP4, M4V, MOV, WebM and MKV files with H.264, HEVC, VP8, VP9 or AV1 video work, as long as your browser can decode that codec. Older formats such as AVI or FLV need converting to MP4 first.
How long does resizing take?
It depends on the length, the resolution and your device. Short HD clips usually finish in seconds on a laptop; long 4K files can take several minutes. The progress bar shows the percentage and an estimate of the time left, and Cancel stops it at once.