Resize your video for every feed.

Drop a video and get it back as 9:16 for TikTok, Reels and Shorts, 4:5 or 1:1 for a feed post, or 16:9 for YouTube: cropped to fill with the part you choose in frame, or fitted whole.

Your video never leaves this device. Your browser reads it and writes the new file right here. Nothing is uploaded or saved.

How to resize a video for TikTok, Reels and YouTube

No account, nothing to install.

Drop your videoAn MP4, MOV or WebM from your phone, camera or screen, up to 5 minutes long. A sample shows until you do.
Pick a shape9:16 for TikTok, Reels and Shorts, 4:5 for a feed post, 1:1 for a square and 16:9 for YouTube.
Choose how it fitsCrop to fill and drag the picture to keep your face in frame, or fit the whole picture over a blurred copy of itself or black bars.
Make and save itYour browser writes an MP4 with 1080 pixels on the short side and your original sound. Save it, then upload it where you post.

The sizes it writes:
9:16 is 1080 × 1920, 4:5 is 1080 × 1350, 1:1 is 1080 × 1080, 16:9 is 1920 × 1080

Resizing videos, answered.

Should I crop or fit?

Crop when you or your product sit in one part of the frame: the video fills the shape, and you drag the picture to keep the right part in. Fit when the edges matter, as in a screen recording or a wide shot: the whole picture stays, over a blurred copy of itself or black bars.

Does cropping lower the quality?

It enlarges part of the frame. A 9:16 crop of a 1920 × 1080 video keeps about 608 × 1080 pixels and stretches them to 1080 × 1920, so it looks softer than the original. Film in 4K, or in the shape you’ll post, for a sharp crop.

What file does it make?

An MP4 of H.264 video at 1080 pixels on the short side, at your video’s own frame rate, with your sound. It’s named after your file and the shape, so clip.mov comes back as clip-9x16.mp4. Where each shape is posted is in the aspect ratio guide.

Does it keep the sound?

Yes. AAC sound, what phones record, is copied into the new file untouched; other sound, such as a WebM’s Opus, is encoded as AAC. If your browser can do neither, the tool says so and makes nothing, rather than a silent video.

Which browsers and files work?

Current Chrome and Safari 26 on a Mac, with MP4, MOV and WebM files up to 5 minutes long. The finished file is held in this tab’s memory until you save it, which is why longer videos are refused. A browser that can’t write video says so here and still previews each shape.

Is my video uploaded?

No. Your browser decodes it, redraws every frame in the new shape and writes the MP4 on this device, with WebCodecs and the open-source Mediabunny library (MPL-2.0). Nothing is sent or saved.

Can I get 9:16, 4:5 and 1:1 at once?

This tool makes one shape at a time. Bang AI’s Export Pack makes 9:16, 4:5 and 1:1 at once, each with and without captions, on iPhone and the Mac.

Want the whole video cut for you?

Film your script and press Auto Edit. Bang AI cuts the ums, pauses and false starts, adds captions and drops in your product shots. Bang AI is on iPhone, the web and the Mac.

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