Fit a video to the shape each platform wants without stretching it: fill the space with a blurred copy, crop to fill, or add colour bars. A live preview shows the result before you start.
Every frame is redrawn into the new shape and saved as an H.264 MP4. To make a file smaller in MB instead, use Compress video. Runs on your device: the video is never uploaded. Works in Chrome, Edge, Opera and Samsung Internet (Android and computers), Safari 16.4 or later (iPhone, iPad and Mac; sound needs Safari 26), and Firefox 130 or later on computers. Firefox for Android can't encode video yet.
How to resize a video
Choose a video, then the shape: 9:16 for Reels, TikTok and Shorts, 4:5 or 1:1 for feed posts, 16:9 for YouTube.
Choose how to fill the frame: blurred background, crop to fill (and where to crop), or colour bars. The preview updates as you change them.
Pick Full HD or HD, press Resize, then download the MP4.
Which shape for which platform
Shape
Size (Full HD)
Use it for
9:16 vertical
1080×1920
Instagram Reels and Stories, TikTok, YouTube Shorts
4:5 portrait
1080×1350
Instagram and Facebook feed posts
1:1 square
1080×1080
Feed posts on any platform
16:9 landscape
1920×1080
YouTube, TVs and laptops
Example
A 1920×1080 landscape video made 9:16 at 1080×1920: with Crop to fill it is scaled to 3413×1920 and only a 1080-wide slice shows, so 68% of the picture is cut away. With Blurred background it is scaled to 1080×607.5 and placed 656 pixels from the top, with the blurred copy above and below.
Tips
Keep text and faces away from the edges: apps put buttons and captions over the bottom and right of vertical videos.
Video files are read and written with Mediabunny 1.61.3 (Mozilla Public License 2.0), loaded unmodified as a separate file, and coded by your browser's own video and audio encoders (WebCodecs). Licence and source code.
Frequently asked questions
What size is a Reel, TikTok or YouTube Short?
All three are vertical, 9:16. 1080×1920 is the usual full HD size; Meta recommends 1440×2560 for Reels ads, and YouTube Shorts are shown at up to 1080p. Instagram's feed shows portrait 4:5 (1080×1350) posts largest. Checked on 7 October 2026.
Blurred background, crop or bars: which is best?
A blurred background keeps the whole picture and fills the empty space with a soft, darkened copy of the video, the usual look for landscape clips posted vertically. Crop to fill uses the whole screen but cuts away the sides (68% of a 16:9 picture in a 9:16 frame); slide the crop position to keep the subject. Bars keep the whole picture on a plain colour.
Will my video be stretched?
No. The picture always keeps its shape; only the frame around it changes.
How long can a YouTube Short be?
YouTube says up to 3 minutes. The tool warns when a 9:16 video is longer; trim it first with Trim video.
Is my video uploaded?
No. Every frame is redrawn and encoded on your device with your browser's own H.264 encoder, so nothing leaves it.
