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Utility

Image Cropper Online - Free & Aspect Ratio Crop Tool

Runs locally · no upload

Free online image cropper supporting 1:1, 4:3, 16:9, 3:4, 9:16 fixed ratios and free crop. Drag to select or input exact pixel values. Pure browser Canvas, keeps PNG transparency, no upload.

Overview

Crop JPG, PNG and WebP images locally in your browser. Choose free crop or one of the 1:1, 4:3, 16:9, 3:4 and 9:16 ratios. Drag-to-select or enter exact pixel values, with PNG transparency preserved. Everything runs in Canvas - your files never leave the device.

How to use

  1. Click "Choose image" to upload a JPG / PNG / WebP (up to 8000x8000 px)
  2. Pick free crop or a 1:1, 4:3, 16:9, 3:4, 9:16 ratio
  3. Drag the green crop box in the preview, or fine-tune origin and size on the right
  4. Pick an output format (auto follows source to keep PNG transparency)
  5. Click "Crop & preview", then download the result locally

Formula

Crop mapping: ctx.drawImage(source, cropX, cropY, cropWidth, cropHeight, 0, 0, cropWidth, cropHeight); aspect lock: cropHeight = cropWidth / aspectRatio (e.g. 16/9 for 16:9); bounds clamp: cropX + cropWidth <= imageWidth, cropY + cropHeight <= imageHeight; PNG alpha kept by skipping fillStyle when output is image/png

Common scenarios

1:1 ID photo crop

Upload a portrait, pick 1:1 ratio and drag the green box around the face. Width and height stay locked equal (e.g. 600x600), then export as JPG for student cards or system avatars.

16:9 video cover

Crop a portrait phone shot into a 16:9 cover for YouTube or Bilibili. Set cropWidth=1920 and the height auto-locks to 1080. Export JPG at quality 92 (200-400 KB) for standard thumbnail dimensions.

3:4 / 9:16 mobile portraits

Use 3:4 for product detail pages or 9:16 for Reels / TikTok. Switching the ratio re-centers the crop box, and on landscape sources height becomes the limiting axis automatically so the crop never overflows.

FAQ

Will my images be uploaded to a server?

No. The tool runs fully in your browser. Files are read into memory via FileReader and re-encoded with Canvas - no fetch or XHR uploads happen. All data is released from memory when you close the tab.

Which input and output formats are supported?

Input: JPG, PNG, WebP, plus formats your browser can decode natively (GIF, BMP). Output: auto (follow source), JPG, PNG, WebP. HEIC / HEIF cannot be decoded by browsers - convert them to JPG/PNG first with our image format converter.

Is PNG transparency preserved after cropping?

Yes. When output is auto (source is PNG) or explicitly PNG, the canvas is never filled with white, so the alpha channel is preserved. Picking JPG output instead fills transparent pixels with white because JPG has no alpha support.

What's the difference between fixed-ratio and free crop?

Free crop accepts any width and height - useful for editing or asset cleanup. Fixed ratios lock the width-to-height proportion, ideal for ID photos (1:1), video covers (16:9) or vertical content (9:16). Switching ratios auto-centers the crop box so you never have to compute dimensions by hand.

What ratios are typical for ID photos and how do I crop them?

Standard one-inch and two-inch ID photos in mainland China are roughly 1:1, while passport and visa photos are usually 35x45 mm (~7:9, use free mode to enter exact values). Pick 1:1, center on the face, and set cropWidth to a clean number such as 600, 800 or 1200 px. JPG export is small and most compatible.

Does it work on mobile? Is touch dragging smooth?

Yes. The green crop box listens to both mouse and touch events (touchstart / touchmove / touchend) and works smoothly on iOS Safari and Android Chrome without triggering page scroll. You can also enter exact pixel values in the number inputs to avoid finger inaccuracy.

What is the maximum supported image size?

Up to 8000x8000 px (~64 megapixels), which covers most phones and DSLRs at full resolution. Larger images show an 'image too big' warning - shrink them to 4000-6000 px first with our image compressor to avoid browser memory pressure.

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