Crop Video

About Crop Video

This online tool allows you to crop videos directly in your browser. Perfect for removing unwanted edges, zooming into specific areas, or changing aspect ratio for social media. Choose preset aspect ratios (1:1, 9:16, 16:9, 21:9) or define a pixel-exact custom crop, then downscale to a delivery resolution (4K, 1080p, 720p, 480p) and export a web-optimized faststart MP4 in one pass. All processing happens locally with FFmpeg.wasm for complete privacy.

What video formats are supported?

You can upload MP4, WebM, MOV, and other common video formats. The cropped video can be exported as MP4 or WebM.

How do I choose the crop area?

You can use preset aspect ratios (Square, Portrait, Landscape, Cinema) with automatic positioning, or define custom width, height, and position in pixels.

What aspect ratios are available?

Preset options include Square (1:1) for Instagram, Portrait (9:16) for TikTok/Stories, Landscape (16:9) for YouTube, and Cinema (21:9) for widescreen.

Can I position the crop area?

Yes! For preset aspect ratios, you can choose from 9 positions: center, corners, and edges. For custom mode, specify exact X and Y pixel coordinates.

Does cropping reduce video quality?

Cropping itself doesn't reduce quality - you're just selecting a region. However, re-encoding may slightly affect quality. Choose High quality setting for best results.

What happens to video duration?

Cropping only affects the frame dimensions, not the duration. The entire video is cropped from start to finish.

Is my video file safe?

Absolutely! All video processing happens directly in your browser using FFmpeg.wasm (WebAssembly). Your video is never uploaded to any server. Everything stays private on your device.

How long does cropping take?

Cropping time depends on video length and output quality. A 30-second video typically takes 30-60 seconds to crop and re-encode. Because everything runs in WebAssembly memory, very large or long clips (above ~200MB) may be slow or hit browser memory limits; downscale the output resolution to speed things up.

What is the faststart (web-optimized) MP4 option?

Faststart moves the MP4 moov atom to the front of the file. This lets the video begin playing and seeking before it is fully downloaded — essential for progressive streaming and web delivery. It is enabled by default for MP4 output and adds no quality loss.

Should I export H.264 (MP4) or VP9 (WebM)?

H.264 MP4 is the safest choice for universal playback, social uploads and faststart streaming. VP9 in WebM produces smaller files at similar quality and is great for modern browsers and web delivery, but encodes slower in the browser. Pick MP4 for compatibility, WebM/VP9 for size.

How do quality settings and CRF affect file size?

Quality maps to a CRF value: lower CRF means higher quality and a larger file, higher CRF means smaller files with more compression. High keeps near-source quality, Medium balances size and quality, Low favors small files. Combine a lower output resolution (e.g. 1080p or 720p) with Medium quality for delivery-ready sizes.

Will my audio be re-encoded, and how is rotation handled?

Cropping never touches audio. When the source audio codec is already compatible with the output container (AAC for MP4, Opus for WebM) the audio stream is copied with no generational loss; otherwise it is re-encoded. Rotation and SAR metadata from phone clips are read from the real stream so the crop targets the correct displayed frame.