Sharpen an image
Crisp up a slightly soft photo with a proper unsharp mask.
- Runs on your device — the file is never sent anywhere
- No sign-up, no watermarks, no daily quotas
- Free, with no limit on how often you use it
How it works
Sharpening does not add detail. It raises the contrast along edges so that the detail already there reads more clearly — which is genuinely useful on a slightly soft scan or a photo that lost its bite during resizing, and useless on something badly out of focus.
What an unsharp mask actually does
The name is backwards and confuses everyone. A blurred — unsharp — copy of the image is made, and the difference between the original and that blur is the edge detail. Adding that difference back amplifies the edges. It is the same method every photo editor has used since it was a darkroom technique with film.
The three controls
Amount is how strongly the edge detail is added back. Radius is how wide an edge counts as an edge: 1 pixel for fine detail, higher for softer, larger-scale contrast. Threshold is the one people skip and should not — it tells the tool to ignore differences smaller than a given amount, which stops it sharpening film grain, sensor noise and JPEG artefacts into something much worse.
How to tell you have gone too far
Bright halos along high-contrast edges — the sky next to a roofline, the outline of a dark branch. Once you can see the halo, everyone can, and it makes a photo look processed rather than sharp. Back the amount off until it disappears.
Sharpen last, and for the size you will use
Sharpening is the final step, after cropping and resizing. A picture sharpened at full size and then shrunk loses the effect; one sharpened after shrinking keeps it.
Sharpen an image — questions
Can it fix a blurry photo?
No. It increases edge contrast in detail that is already there. Genuine motion blur or missed focus cannot be undone.
What settings should I use?
Start around 80% amount, radius 1 and threshold 3. Raise the threshold if the picture is noisy.
What are the halos I am seeing?
Over-sharpening. Bright outlines along high-contrast edges mean the amount is too high.
Should I sharpen before or after resizing?
After. Sharpen last, at the size you will actually publish.
Are my photos uploaded?
No. Everything happens in your browser.