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Video & Audio Tools

Video Aspect Ratio Converter

Make one video fit every platform. Convert landscape video to vertical 9:16 for Reels, TikTok and Shorts, to square or 4:5 for feeds, or vertical video back to 16:9 for YouTube. Keep the whole picture with a blurred background or coloured bars, fill the frame by cropping, or stretch if you must. The output keeps the source detail without needless enlargement.

  • Files stay on your device
  • No sign-up
  • Free to use

How to use Video Aspect Ratio Converter

  1. Drop a video onto the page.
  2. Choose the new aspect ratio.
  3. Choose blur, bars, crop or stretch.
  4. Convert and download the MP4.

Video Aspect Ratio Converter features

Social formats

9:16, 1:1, 4:5, 16:9, 4:3, 21:9.

Blurred background

The popular look for vertical video.

Bars in any colour

Classic letterbox or pillarbox.

Crop to fill

Centre crop.

Size shown

Output dimensions before converting.

Private

Processed on your device; the video is never uploaded.

When to use Video Aspect Ratio Converter

  • Posting YouTube videos as Reels, TikToks and Shorts.
  • Using phone videos in landscape presentations.
  • Square videos for feeds and ads.
  • Letterboxing for cinematic looks.

Video Aspect Ratio Converter FAQ

Which fit should I choose?

Blurred background keeps everything visible and looks natural on phones; crop fills the screen but cuts the sides; bars are neutral and classic; stretch distorts and is rarely a good idea.

What size is the output?

For blur and bars the frame grows around the original so no pixels are lost; for crop the frame fits inside the original. Sizes are limited to 4K.

Can I choose what part is kept when cropping?

The centre is kept. For a different area, use the Video Cropper.

Is the sound kept?

Yes, the audio is kept and encoded as AAC.

Why does the first run take longer?

The media engine, FFmpeg compiled to WebAssembly (about 32 MB), is downloaded once and then cached by your browser.

Is my video uploaded?

No. FFmpeg runs as WebAssembly in your browser, so the video stays on your device.

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Fitting video into another shape

Different platforms favour different shapes: YouTube and TVs are 16:9, phones held upright are 9:16, social feeds prefer square or 4:5. Re-shooting for every platform is rarely possible, so videos are converted, and there are only a few ways to do it.

Fitting the whole picture into a different shape leaves empty areas. Classic bars – letterboxing above and below or pillarboxing at the sides – fill them with a solid colour. The blurred background fills them with an enlarged, blurred copy of the video itself, which keeps the colours and movement of the scene and has become the standard look for landscape clips on vertical platforms.

Cropping instead fills the frame and cuts off what does not fit. It works well when the subject is in the centre; for a different area, crop manually first. Stretching changes the proportions of everything in the picture and is rarely acceptable.

The converter computes the output size from the source so that no detail is wasted: fit modes grow the frame around the original, crop mode stays inside it. Dimensions are rounded to even numbers and capped at 4K.

All processing happens in your browser.

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