Video Resizer for Social

Resize a video for social media

Social networks show video in different shapes. A landscape video in a vertical frame leaves empty space above and below it, and a vertical video in a landscape frame leaves wide bars at the sides. This video resizer turns a video into the shape you need: vertical 9:16, square 1:1, portrait 4:5 or landscape 16:9, or any custom shape. You can crop it so the picture fills the frame, or fit the whole picture on a blurred or colored background. It all runs in your browser, so the video is never uploaded.

• Landscape to vertical: turn a 16:9 clip into a 9:16 video for Reels, TikTok, Shorts or Stories.
• Vertical to landscape: put a phone video on a 16:9 frame with a blurred background, for YouTube or a presentation.
• Square and 4:5: make feed posts that take up more height on a phone held upright than a landscape video at the same width.

Crop or fit with a background

Crop to fill cuts the sides (or the top and bottom) off so the picture fills the new shape. The tool takes the largest area of the new shape that fits in the video and lets you move it with the position slider or by dragging the frame in the preview: 0 percent is the left or top edge, 100 percent the right or bottom edge. Cropping a 1920 × 1080 video to 9:16 keeps a 608 × 1080 area, less than a third of the width, so place it on the part that matters.

Fit with background keeps the whole picture, scaled to fit, and fills the rest of the frame. With Blurred video, the background is the same video, enlarged to fill the frame, blurred and slightly darkened, so it moves with the picture. With Color, it is a solid color you pick, like black or white. This works well for screen recordings, slides and group shots where nothing may be cut off.

The preview shows a frame from your video with the crop area or the finished layout. Use the preview frame slider to check other moments, for example whether a person walks out of the cropped area later in the clip.

Output sizes and platform specs

For each shape the tool offers four sizes by the short side: 1440, 1080, 720 and 540 pixels, so 9:16 at 1080 is 1080 × 1920 and 4:5 at 1080 is 1080 × 1350. Widths and heights are always even numbers, the same rule mediabunny applies for video encoders. The size menu also lists the video sizes the platforms publish themselves. These come from the same sourced list as our social media image sizes page, checked October 2026:

A minimum is the smallest size the platform accepts and a maximum the largest; recommended is the size the platform suggests. YouTube does not publish a pixel size for Shorts, only that they are square or vertical. Specs can change, so check the linked help page before an ad campaign.

Choosing a size larger than the part of the video you use makes the tool enlarge it, which looks softer and adds file size without adding detail. The tool tells you when that happens. If the file is too big for an upload afterwards, the video compressor can make it smaller.

What happens to your video

The tool reads MP4, MOV, WebM and MKV files with mediabunny, an open-source media library, and uses the WebCodecs API of your browser to decode and encode the frames. In crop mode, mediabunny cuts and scales each frame. In fit mode, each frame is drawn onto a canvas with its background and handed back to the encoder with its original timestamp, so the timing and the sync with the sound stay as they were. The new file is an MP4 with H.264 video when your browser can encode it, otherwise a WebM with VP9. The picture is re-encoded, so it loses some fine detail. AAC sound in an MP4, or Opus or Vorbis sound in a WebM, is copied unchanged; other sound is re-encoded as AAC for MP4 or Opus for WebM. File sizes on this page use decimal units: 1 KB is 1,000 bytes and 1 MB is 1,000,000 bytes. Metadata tags of the original file are not copied.

Browser support and iPhone

According to MDN, the WebCodecs VideoEncoder is available in Chrome and Edge 94 or newer, in Firefox 130 or newer on computers and in Safari 16.4 or newer, which covers iPhone and iPad. Firefox for Android does not have it. Which codecs and sizes the encoder accepts depends on the device, so the tool asks the browser before it starts and tells you if something does not work.

On iPhone and iPad, two things work differently. Re-encoding sound needs the AudioEncoder, which MDN lists only from Safari 26, so on older versions sound that cannot be copied as it is gets left out, with a note. And MDN lists the canvas blur filter in Safari only behind a setting, so the tool blurs the background by shrinking and enlarging it there, which looks a little coarser. The finished video is held in memory until you download it, so very long videos can fail on phones; cut them shorter with Trim Video first.

How to use the video resizer

1. 1Drop a video on the box, or tap it to pick one from your files or photo library.
2. 2Pick the shape and choose Crop to fill or Fit with background. Move the crop area or pick the background, and check the preview at a few moments.
3. 3Choose the output size, press Resize video and wait until the bar is full. Watch the result and press Download video.

Open-source software

Reading, cutting, scaling and writing the video files is done by mediabunny, licensed under the Mozilla Public License 2.0 (MPL-2.0). The encoding itself is done by your browser.

Sources

• MDN: VideoEncoder: browser compatibility (Chrome and Edge 94, Firefox 130 on desktop, not Firefox for Android, Safari 16.4 including iOS)
• MDN: AudioEncoder: browser compatibility (Safari 26)
• MDN: CanvasRenderingContext2D.filter: Safari only behind a setting
• mediabunny: Converting media files: cropping, resizing and processing frames while keeping their timestamps
• mediabunny: Supported formats and codecs: MP4, MOV, WebM and MKV
• Platform video sizes: the help page linked in each row of the table above
• mediabunny license (MPL-2.0)

Built by Tobias Kurth, designer. Updated October 14, 2026.

Frequently asked questions