Loading page
About this tool
Interactively compare different blur intensities on your images with a side-by-side slider.
Blur Comparison applies the CSS Gaussian blur filter to an image at a radius you choose from 1 to 100 pixels and splits the view down a draggable line, so the sharp original and the blurred version sit side by side in the same frame. It is for anyone who has to pick a blur strength by eye rather than by guessing a number — designers testing a background, or someone obscuring a detail in a screenshot. The chosen radius exports as a PNG rendered at the image's full native resolution.
Open Blur Comparison on AltFTool — it loads instantly in your browser.
Drop a photo onto the 'Drop your photo here or click to upload' panel, or click it to browse. JPG, PNG and WebP are supported, and the Interactive View header then shows the image's pixel dimensions.
Set the strength with the Intensity slider under Blur Settings — 1px to 100px, with the current value shown in the px badge beside it — or hit the Subtle, Medium and Heavy presets for 5px, 15px and 40px.
Drag the white handle across the preview to wipe between the blurred left side and the untouched Original right side, or jump to Original, 50 / 50 and Blurred under Slider Position. Export saves the blurred copy as blurred-<intensity>px.png, and Reset returns to 10px at the halfway point.
The split slider puts the two states edge to edge on the same picture, which reads the difference far more accurately than toggling back and forth.
The intensity you settle on is the same number you paste into a filter: blur() rule, with no conversion or guesswork.
The download re-renders the blur onto a canvas at the image's original pixel dimensions instead of saving the on-screen preview.
There is no single safe number — it depends on how large the text is in the image, so drag the slider until the characters are unrecoverable rather than trusting a preset. The Heavy preset here is 40px against a 1 to 100px range, and for anything genuinely sensitive a solid box or pixelation is safer than blur, because blur is a reversible mathematical operation in principle.
Yes. The preview applies the standard CSS filter blur() with the pixel radius shown on the slider, so setting 12px here and writing filter: blur(12px) in your stylesheet produces the same Gaussian falloff. The presets map to 5px for Subtle, 15px for Medium and 40px for Heavy.
Yes, the export draws to a canvas sized to the image's natural width and height, so a 4000 x 3000 photo comes back at 4000 x 3000 as a PNG. Only the blurred version is exported; the original is untouched on your device.
Not simultaneously — the split view compares exactly one blur radius against the untouched original. To weigh two candidate radii against each other, export each one and compare the two files, or step the slider between them while watching the same region of the image.