Image Round Corners
Apply rounded corners, a full circle mask, or per-corner radii to an image — preview with a checkerboard for transparency, download as PNG or JPEG.
How to use
- Drop an image. Pick a mode — uniform radius for a normal rounded card, circle for an avatar from a square, squircle for an iOS-style shape.
- Per-corner mode gives you four sliders if you need an asymmetric clip (a chat-bubble corner, for example).
- Download as PNG to keep the transparent corners, or JPEG if size matters more than alpha.
About this tool
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Clips an image with a rounded-rectangle (or circle, or squircle) path baked into a transparent PNG. Useful for avatar squares, thumbnail tiles, and any image that needs to match a border-radius styling without doing it in CSS. The per-corner mode takes four independent radii (top-left, top-right, bottom-right, bottom-left); padding adds an opaque border around the clip; JPEG mode flattens transparency to a chosen background color since JPEG can't carry alpha.
Baking the corners into the file is the right move in exactly the places CSS cannot reach: an email client that strips most styling, a PDF, a slide deck, a printed sheet, or an app that renders the raw image. Everywhere else, border-radius is better because the same asset then works at any size and the corner scales with the box. A radius baked at 24 pixels looks wrong the moment the image is displayed at half its dimensions.
The squircle is not a rounded rectangle with a bigger radius. It is a superellipse, a continuous curve with no point where a straight edge meets an arc, and that discontinuity is what the eye notices on a normal rounded corner at large radii. It is why iOS icons use one, and it is also why an icon drawn as a squircle and clipped as a rounded rectangle looks subtly wrong next to its neighbours.
Alpha is a property of the format, not of the image. PNG and WebP carry it; JPEG does not, which is why the JPEG path asks for a background colour rather than silently filling with black. If the result will sit on an unknown background, keep it PNG.
The canvas clips on pixel boundaries with antialiasing, so a curve is a few partially transparent pixels rather than a hard edge. That is what makes it look smooth, and it is also why scaling the output down afterwards can leave a faint halo of the original background.
Frequently asked questions
What's a squircle?
A continuous-curvature shape between a circle and a square — the iOS app icon shape, Apple's 'superellipse' (n≈4). It looks softer than a rounded rectangle because the curvature doesn't have an abrupt straight-to-curve transition.
Why does my output have a checkerboard background?
That's just the preview showing the transparent area. The downloaded PNG keeps the real transparency — drop it into a page and the corners will be see-through.
The corners came back square after I saved as JPEG. Why?
Because JPEG has no transparency. The rounded area has to become some colour, and that colour is whatever the encoder fills with — usually black or white — so the rounding disappears against a page of a different colour. Save as PNG or WebP when the corners need to be see-through, and use JPEG only when you are placing the image on a known, matching background.
Should I round the image or round it in CSS?
Round it in CSS wherever the image appears on a page you control: border-radius costs nothing, adapts to any size, and leaves the original file intact for other uses. Bake the corners into the pixels only when the destination cannot style them — an email client, a document, a platform that renders your upload as-is — since a baked radius is fixed at one size and cannot be undone.
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