Question 1

Why download a rounded image instead of just using CSS border-radius?

Accepted Answer

CSS border-radius only rounds an image inside a browser that supports it, it does nothing to the underlying file. This tool bakes the rounded corners into the actual image data, so it looks correct anywhere the file is used: app icons, PDFs, email templates, or platforms that don't respect CSS.

Question 2

What does "Smooth corners" actually change?

Accepted Answer

A normal rounded corner is a quarter circle, so the curve starts abruptly: the edge runs perfectly straight up to the point where the arc begins, then bends at full strength. The eye reads that break as a slight flattening, which is why Apple's icons use a superellipse, the shape people call a squircle. Ticking the option traces each corner as a superellipse quadrant instead, so the bend starts earlier and eases into the straight edge with no visible join. It shows on large shapes like icons and logos, and is invisible on a thumbnail with an 8px radius.

Question 3

How do I get a perfect circle?

Accepted Answer

Tick "Crop to a square first" and drag the radius to Max, leaving "Smooth corners" off (with it on, the same settings give the iOS app icon outline rather than a circle). Without the crop, a rectangular image at maximum radius becomes a stadium (pill) shape instead, because the curve can never exceed half the shorter side. The crop takes the centre square of your photo, which is what an avatar needs anyway.

Question 4

Can I round only some of the corners?

Accepted Answer

Yes. Tick "Set each corner separately" and you get four sliders, one per corner. That covers the common card pattern where an image is rounded on top and square where it meets the text below, and lets you build asymmetric shapes like a chat bubble with one square tail corner.

Question 5

Should I set the radius in pixels or percent?

Accepted Answer

Pixels when the output size is fixed and you know the exact curve you want. Percent when the same treatment has to work across images of different sizes, since it's measured against the shorter side: 10% looks the same on a 400px thumbnail and a 4000px photo. It follows CSS rules, so 50% is already a full circle.

Question 6

Which format should I download?

Accepted Answer

WebP if the destination accepts it, since it keeps transparency and is usually the smallest of the three. PNG for anything older that still needs transparent corners, at the cost of a much larger file for photographs. JPG only when the image sits on a known background, because it has no alpha channel and the corners have to be filled with a solid color. The size estimate under the preview updates as you switch, so you can see the difference before downloading.

Question 7

Why would I reduce the output size?

Accepted Answer

Because the radius, the corner shape and the compression all apply to the pixels you actually ship. A 4000px photo rounded for a 256px avatar slot wastes bandwidth and gets resampled by whatever displays it anyway. Scaling here means the corner you previewed is the corner in the file, rather than a curve that shrinks with the image later. Use a preset or type any value: it sets the longest side and the other one follows the aspect ratio, so a portrait 800 × 1200 set to 512 comes out 341 × 512. Anything at or above the original is treated as Original, since inventing pixels that were never captured only makes the file bigger.

Question 8

Is my image uploaded to a server?

Accepted Answer

No. The file is read and processed with the Canvas API entirely in your browser. It never leaves your device, and nothing is stored once you close or refresh the page.

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Image Corner Rounder

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