How to Resize a Video (Any Size, No Upload)

Open [Resize Video](/resize-video), drop in your file, pick a size preset, pick a fit mode, and download the MP4. The presets are 1080p, 720p, 480p, 360p, plus three social shapes: 9:16 vertical (1080×1920), 1:1 square (1080×1080), and 4:5 portrait (1080×1350). The default is 720p. The tool runs ffmpeg.wasm inside your browser tab, so the video is never uploaded. Output is always MP4, whatever you put in. The one decision that matters is the fit mode, because it controls what happens when your video and the target size have different shapes. The next section covers that.

Use Fit when nothing can be cut off. It keeps the whole picture and adds black bars where the shapes differ. Use Fill when the frame must be full. It scales the video up until it covers the frame, then crops whatever spills over the edges. Use Stretch almost never. It forces the picture to the new size and distorts it whenever the shapes differ, so faces get wide or thin.

If your source and target share the same shape, for example 4K to 1080p, all three modes give the same result. The choice only matters when the aspect ratios differ. A slideshow, screen recording, or anything with text near the edges belongs in Fit. A talking-head clip with empty space around the subject usually works in Fill.

Pick the preset that matches where the video will be posted. 9:16 (1080×1920) is for Reels, TikTok, and YouTube Shorts. 1:1 (1080×1080) is for square Instagram and Facebook posts. 4:5 (1080×1350) is for Instagram feed portrait posts.

The catch is that most source footage is 16:9 landscape, so the crop math is harsh. Filling a 1920×1080 clip into 9:16 keeps only about 32% of the width, because the picture is scaled to 1920 tall and then cropped to 1080 wide. Square keeps about 56%, and 4:5 keeps about 45%. If people or text sit at the sides, Fill will cut them out. Choose Fit instead and accept the black bars, or trim the shot first with [Crop Video](/crop-video) so the subject sits in the middle. For sizing rules beyond video, see [social media image sizes](/blog/social-media-image-sizes).

Choose 1080p (1920×1080) for full HD, 720p (1280×720) for a lighter HD copy, 480p (854×480) for standard definition, and 360p (640×360) as the smallest landscape option. In the tool, 720p is described as about half the file size of 1080p, and 480p as small enough for most email limits. Those are the practical use cases: 720p for messaging apps and quick sharing, 480p when an attachment has a size cap.

All output dimensions are even numbers. That is deliberate: the H.264 encoder with yuv420p output rejects odd widths and heights, so every preset is built from even values. If you ever resize by hand in another tool and get an error about dimensions divisible by 2, this is the reason.

Resizing changes the number of pixels. Compressing changes how aggressively those pixels are encoded. Fewer pixels usually means a smaller file, which is why 720p is lighter than 1080p, but the two are separate controls. If you only need a smaller file at the same dimensions, use [Compress Video](/compress-video) instead, and see [compress video online](/blog/compress-video-online) for how that works.

One caution in the other direction: upscaling does not add detail. Turning a 480p clip into 1080p gives you a bigger frame with the same information in it, and the file usually gets larger, not better. Resize up only when a platform demands a minimum size. Otherwise, keep the original resolution and resize down.

Resizing a video always re-encodes it, unlike removing audio, which can copy the video stream untouched. The tool rewrites every frame with the libx264 encoder at CRF 23, a moderate quality setting, so the output is not a lossless copy of the original. Expect a small generational loss, and avoid resizing the same file repeatedly. Keep the original and resize from it each time.

Audio is copied through untouched when the MP4 container can hold it. If it cannot, the tool falls back to AAC at 192k instead of failing. Sources with non-square pixels are set to square pixels on output so they do not play back stretched. One known limit: anamorphic sources are fitted using their coded size, so a widescreen clip stored in a squeezed frame may not come out in the shape you expect.

The resize runs entirely in your browser with ffmpeg.wasm. The file is read into your tab's memory, processed there, and handed back as a download. Nothing is sent to a server, and there is no account or watermark. That is useful for client footage, unreleased material, or anything personal.

The result is named after your original file with the new size added, for example holiday-1280x720.mp4. Because processing happens on your own device, how long it takes depends on your computer and the length of the clip. If you only need part of a long video, run it through [Trim Video](/trim-video) first so the resize has less to process.