Round Image Corners

Features

• Radius in pixels or as a percentage of the short side; 50% is fully round
• Transparent PNG by default; pick a fill colour to get a much smaller JPEG
• Radius clamped to half the short side, so the path never degenerates
• Covers circular avatars, rounded cards and chat avatars in one step
• Download the result directly; the name gains a -rounded suffix
• Images are never uploaded; works offline

How to use

1. Drop your image onto the dashed area
2. Set a radius in pixels or percent — or enter 50 for a circle
3. Need a fill colour? Uncheck transparent and pick one
4. Download the result

FAQ

Why is the output a PNG rather than a JPEG?

Because the cut-away corners should be transparent — then the image works on any background. JPEG has no alpha channel, so those corners can only be one fixed colour, and the moment your page background differs, four patches appear. The tool therefore defaults to PNG and only produces a JPEG when you explicitly choose a fill colour (much smaller, and right for white-background avatars).

How do I make a circular avatar?

Set the unit to percent and the value to 50 — that is fully round (radius equal to half the short side). If the source is not square you get an ellipse, not a circle; crop to a square first if you need a true circle. Most platforms (WeChat, GitHub, countless admin panels) crop a square image into a circle themselves, so often being square is all that matters.

Why does a very large radius change nothing?

Because past half the short side the corners cannot round any further — they have already consumed the whole edge, leaving one continuous arc. The tool clamps there, which is also what makes “maximum rounding” a well-defined setting. On a very wide image (800×200, say) a 100px radius is already close to the limit.

Are the rounded edges aliased?

No. The drawing uses canvas path clipping, and the browser antialiases by coverage — rather than drawing first and erasing the corners, which removes pixels and leaves a hard, half-transparent edge. Watch the output format too: PNG keeps the full alpha channel, whereas JPEG blends those semi-transparent edge pixels with the fill colour before compressing, so use PNG whenever the corners must be transparent.