What is the difference between pad and crop mode?

Pad mode adds black letterbox or pillarbox bars so the entire original frame is preserved inside the new aspect ratio. Crop mode zooms the source so it fills the new ratio completely — useful when you want no bars, at the cost of clipping the edges.

Which target aspect ratios are supported?

Choose 16:9 (1280×720) for YouTube and TVs, 9:16 (720×1280) for TikTok/Reels/Shorts, 1:1 (720×720) for Instagram feed, 4:3 (960×720) for classic monitors, or 21:9 (2560×1080) for ultrawide cinematic framing.

Will the output keep the original resolution?

The output uses a fixed canvas size per preset (e.g. 1280×720 for 16:9). If your source is higher resolution, it will be scaled to fit the canvas — this keeps file size reasonable while staying compatible with every platform.

When should I use pad versus crop?

Use pad when preserving every part of the original is important — interviews, gameplay, captioned content. Use crop when the framing is flexible and you want a clean, edge-to-edge result for social feeds.

Does this re-encode the audio?

No. Only the video stream is re-encoded; audio is stream-copied. That keeps audio bit-perfect and makes encoding much faster than tools that re-encode the whole file.

Is the video uploaded?

No. ffmpeg.wasm runs entirely inside your browser. The file stays on your device — nothing is transmitted to any server.

Change Video Aspect Ratio

Convert any video to 16:9, 9:16, 1:1, 4:3 or 21:9 — pad with black bars or zoom to fill. All in-browser.

100% client-side · no upload

Video file (MP4, WebM, MOV…)

Load a video file to begin.

How to change a video's aspect ratio

Select your video file — MP4, WebM, MOV all work.
Choose the target aspect ratio you need for your platform.
Pick Pad to preserve the full frame with black bars, or Crop to fill and zoom.
Click Apply aspect ratio and download the result.

Common use cases

Landscape to vertical: Take a 16:9 YouTube recording and republish as a 9:16 TikTok or Reel.
Vertical to square: Reformat a portrait phone clip to 1:1 for the Instagram feed.
Wide cinema look: Crop a standard 16:9 clip to a 21:9 ultrawide cinematic frame.
Old footage rescue: Reformat 4:3 standard-definition content for modern 16:9 displays.

Related tools: Video Cropper · Video Resizer · Video Rotator · Video Compressor

常见问题

What is the difference between pad and crop mode?: Pad mode adds black letterbox or pillarbox bars so the entire original frame is preserved inside the new aspect ratio. Crop mode zooms the source so it fills the new ratio completely — useful when you want no bars, at the cost of clipping the edges.
Which target aspect ratios are supported?: Choose 16:9 (1280×720) for YouTube and TVs, 9:16 (720×1280) for TikTok/Reels/Shorts, 1:1 (720×720) for Instagram feed, 4:3 (960×720) for classic monitors, or 21:9 (2560×1080) for ultrawide cinematic framing.
Will the output keep the original resolution?: The output uses a fixed canvas size per preset (e.g. 1280×720 for 16:9). If your source is higher resolution, it will be scaled to fit the canvas — this keeps file size reasonable while staying compatible with every platform.
When should I use pad versus crop?: Use pad when preserving every part of the original is important — interviews, gameplay, captioned content. Use crop when the framing is flexible and you want a clean, edge-to-edge result for social feeds.
Does this re-encode the audio?: No. Only the video stream is re-encoded; audio is stream-copied. That keeps audio bit-perfect and makes encoding much faster than tools that re-encode the whole file.
Is the video uploaded?: No. ffmpeg.wasm runs entirely inside your browser. The file stays on your device — nothing is transmitted to any server.

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