How to blur a picture
Upload an image and the Effects tab opens with a light blur already applied. Move the Blur slider from 0 to 20 to control the strength. The value is measured against a 600 px wide preview and scaled up to your image's real width when it is rendered, so what you see on screen matches the downloaded file in proportion, even for very large photos.
The blur covers the entire image evenly. The tool cannot blur just one area, such as a face or a number plate. For hiding a specific detail, crop it out, or use a separate tool that lets you select a region.
Good uses for a blurred image
Blurred photos make good backgrounds behind headings on websites, slides and posters, because the colours and mood stay while the detail stops competing with the text. Values around 6 to 12 on the slider usually give that effect. Lower values, around 1 to 3, soften skin, noise or harsh textures without making the picture look obviously blurred.
If you want the subject to stay sharp while only the background is blurred, use Blur Background in the background tools instead. It uses AI to separate the person or object first and then blurs everything behind it, similar to a portrait mode effect.
Blur, pixelate or sharpen
The Effects tab has three sliders. Blur smooths detail with soft edges. Pixelate replaces detail with square blocks, which looks deliberate and is a common way to obscure content. Sharpen does the opposite of blur and increases edge contrast. You can combine blur with brightness or contrast changes, or add text on top, and everything is rendered in one pass on the server. PNG stays PNG, other formats become JPG.