Resize Video for TikTok, Reels and Shorts
Turn a horizontal video into 9:16, square or 4:5 in your browser. Crop to fill the frame and drag the crop where you want it, or fit the whole picture on a blurred, black or coloured background. Your file never leaves your device.
How to resize a video
-
Choose your video
Pick a file or drop it on the box. MP4 and MOV from phones and cameras work best; WebM and MKV open too if your browser can decode them. The file is read in place, not uploaded.
-
Pick the shape
9:16 for TikTok, Reels and YouTube Shorts, 4:5 for the Instagram feed, 1:1 for square posts, or 16:9 to go back to widescreen.
-
Crop or fit
Crop to fill keeps a window of the picture and fills the frame. Drag the box on the source, or use the slider, to keep the speaker in shot. Fit keeps the whole picture and fills the empty space with a blurred copy, black or a colour you choose.
-
Resize and download
Press Resize video. A progress bar shows how far along it is and you can cancel at any time. When it finishes, preview the result and download the MP4.
Which size for which platform
The tool uses these sizes when you pick 1080p. 720p halves the file size and is enough for most phone viewing.
| Shape | 1080p output | Use it for |
|---|---|---|
| 9:16 | 1080 × 1920 | TikTok, Instagram Reels, YouTube Shorts, Stories |
| 4:5 | 1080 × 1350 | Instagram and Facebook feed posts |
| 1:1 | 1080 × 1080 | Square feed posts; also counts as a YouTube Short |
| 16:9 | 1920 × 1080 | YouTube, websites, presentations |
Sizes from our guides to TikTok video size, Instagram Reels size and YouTube Shorts size, which also cover length limits and caption safe zones.
Crop or fit: which one to use
Both give you the right shape. They differ in what you lose.
Crop to fill
Fills the whole phone screen, so it looks native in the feed. You lose the sides of a horizontal video: from 16:9 to 9:16 you keep about a third of the width. Best for one person talking to camera.
Fit, blurred background
Keeps every part of the picture. The empty space above and below is filled with a soft, darkened copy of the same shot, so it looks deliberate rather than letterboxed. Best for screen recordings, slides and wide shots.
Fit, black or colour
The same as blurred, with a flat background. Leaves clean space to add a title or captions in an editor afterwards. Pick a brand colour with the colour picker.
Quality, formats and file size
The video is re-encoded once, at high quality, using your browser’s built-in encoder (WebCodecs). Chrome, Edge and Safari write MP4 with H.264 video, the format every platform accepts. The tool shows the exact format before you start. If your browser has no H.264 encoder, it writes WebM instead and tells you.
Sound is kept. If it is already AAC, as it is from almost every phone, it is copied across untouched. Browsers that cannot encode audio and receive a file with another audio format will produce a silent video, and the tool says so before you download.
Picking Source pixels avoids upscaling. A 1920 × 1080 video cropped to 9:16 has a 608 × 1080 window of real detail; stretching it to 1080 × 1920 adds no detail but matches what the platforms recommend. If you record with vertical clips in mind, record in 4K: the 9:16 crop from 3840 × 2160 is 1215 × 2160.
Speed depends on your device, and the progress bar shows how far along it is. Big files open fine because they are read in pieces; in Chrome and Edge you can also save the result straight to disk so it does not have to fit in memory.
Tips for reframing horizontal video
- Check the whole clip. A fixed crop that frames the speaker at the start may cut them off when they move. Play the preview through before you export, or use Fit for clips with lots of movement.
- Two people in frame? A single 9:16 window rarely holds both. Use Fit with a blurred background, or let Short.now follow whoever is speaking.
- Leave room for the app’s buttons. The bottom and right edge of a vertical video are covered by captions and icons. Our Shorts size guide has the safe zone.
- Trim first. If you only need 30 seconds of a long recording, cut it with the video trimmer first, which copies without re-encoding, then resize the short clip.
Resizing a long video by hand? Let Short.now reframe it.
Short.now takes a long horizontal video, finds the best moments and reframes each one to 9:16 with face tracking, so the crop follows the speaker instead of sitting still. Captions are added for you.
Questions
Choose 9:16 for Reels and Stories or 4:5 for a feed post, pick Crop to fill or Fit with a blurred background, and press Resize video. You get a 1080 × 1920 or 1080 × 1350 MP4 ready to upload.
No. The video is processed by your browser on your own device and nothing is sent to a server. Once you have picked a file, you could disconnect from the internet and it would still finish.
No. The tool is free and the output has no watermark or logo.
Yes. Choose one of the Fit options. The whole picture is kept and the empty space is filled with a blurred copy of the video, black, or a colour you pick.
Any browser with WebCodecs video encoding: Chrome and Edge 94 or later, Safari 16.4 or later on Mac, iPhone and iPad, and Firefox 130 or later on desktop (per MDN browser compatibility data, checked November 2026). Firefox for Android does not support it yet.
There is no fixed limit, because nothing is uploaded. Files over 2 GB work but take a while, and the result must fit in memory unless you save straight to disk (Chrome and Edge).
