Sharpen Image

Make edges crisper with an unsharp mask. Check the detail at 100% before you save. The file you download is the picture you see.

Drag & drop a file here, or

JPG PNG WebP BMP AVIF GIF Up to 50 MP • Processed in browser • Nothing leaves your device

Runs in your browser

Three Real Controls

Radius sets how wide an edge is. Amount sets how hard it is pushed. Threshold keeps flat areas like skin and sky from turning grainy.

Judge It at 100%

A shrunken preview hides both sharpening and halos. The side-by-side crop shows real pixels, and the download is made from the same full-size pass.

Privacy-First

Every pixel is sharpened on your own device. Nothing is uploaded, nothing is stored, and no account is needed.

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How it works

What an unsharp mask actually does

The name sounds backwards. The tool makes a blurred copy of your photo, subtracts it from the original, and what is left is a map of the edges. That map is added back on top, so a dark side of an edge gets a little darker and the light side a little lighter. Nothing new is invented. Contrast that was already there, across an edge, is made steeper, and the eye reads steeper edges as sharper.

Radius, amount and threshold

Radius is how wide the blurred copy reaches, in pixels. Small values under 1 px lift fine texture like hair and fabric; 2 to 3 px lifts larger shapes and starts to show halos. Amount is how much of the edge map is added back: 100% doubles the local contrast step. Threshold is a floor. Edge differences at or under it are left alone, so flat skin, sky and JPEG noise stay smooth while real edges are sharpened.

Why the preview is full size

Sharpening works at the level of single pixels. A preview that is scaled down to fit the screen blends those pixels away, and many tools sharpen only that small preview, so the saved file looks different from what you approved. Here the whole picture is sharpened once at full size. The preview, the 100% crop and the download all come from that one result, and the crop lets you check halos where they actually appear.

Sharpening is not unblurring

A photo blurred by camera shake or a missed focus has lost the fine detail. Sharpening cannot put it back. It will make the blurry edges more contrasty, and past a point it adds halos and grain. For real blur, an AI model that reconstructs detail is the right tool, and Scanly has one in Photo Unblur. Use this page for a photo that is nearly right: a soft lens, a resized image, a scan, or a picture about to be printed.

Frequently Asked Questions

How do I sharpen an image online?

Upload the photo, start with the Standard preset, and look at the 100% crop. If the edges still look soft, raise the amount. If you see bright or dark outlines along edges, lower the amount or the radius. When it looks right, press Download. The saved file is the full-size picture you just checked.

What settings should I use to sharpen a photo?

For most photos a radius of 1 to 1.5 px, an amount of 80 to 120% and a threshold of 2 to 4 works well. After making an image smaller, use a small radius like 0.6 px with a higher amount. For a soft scan or a print, try a radius of 2 to 2.5 px. Always judge at 100%, not on the shrunken preview.

Can this fix a blurry photo?

Only a slightly soft one. Sharpening makes existing edges more contrasty. It cannot recover detail that motion blur or a missed focus has already destroyed, and pushing it hard on such a photo only adds halos and grain. For real blur, use Photo Unblur, which uses an AI model to rebuild detail.

What is the threshold for?

It protects smooth areas. Each pixel is only changed if its difference from the blurred copy is larger than the threshold. Real edges have large differences and get sharpened. Skin, sky and compression noise have small ones and are left alone. A threshold of 0 sharpens everything, including noise.

Why do I see white or dark outlines around edges?

Those are halos, the classic sign of oversharpening. The amount or the radius is too high for this picture. The report under the preview also tells you how many colour values were pushed all the way to pure black or white, which is where halos become visible. Lower the amount first, then the radius.

Is this the same sharpening as in Photoshop or GIMP?

It is the same kind: an unsharp mask with radius, amount and threshold. The exact numbers are not interchangeable between programs, because each one blurs a little differently. This page produces the same pixels as the Pillow imaging library in Python for the same three settings, which is checked by an automated test.

Will sharpening lower the quality of my JPEG?

A JPEG you upload is saved as a JPEG again, at high quality, so it goes through one more round of compression. If you plan to edit the photo further, upload a PNG instead and it will be saved losslessly as PNG. Other formats are saved as PNG as well.

What happens to transparency?

It is kept exactly. Only the colour channels are sharpened, and the alpha channel is copied through untouched, so a cut-out keeps the edge it had. Fully transparent pixels are left as they were. Colours right next to a transparent area can still change slightly, because the blurred copy sees the hidden colour under the transparent pixels.

How large an image can I sharpen?

Up to 50 megapixels. The whole picture is sharpened at full size in your browser, so very large photos take a second or two per change. On large photos the result updates when you let go of a slider rather than while you drag it.

Is my photo uploaded anywhere?

No. The picture is read into your browser and sharpened there. There is no server call, no storage and no account, and closing the tab discards it.

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