A single CSS filter property, without an uploaded image
An 8px blur radius with no file uploaded generates simply: filter: blur(8px); -- shown against a preview box using this CSS filter directly, since there's no actual image loaded to apply it to.
This is the same blur() CSS filter function used across several other tools on this site (like the general CSS Filter Generator) -- here it's isolated and framed specifically around the background-blur use case, where you'd typically apply this filter to a background image element behind other content.
Without an uploaded file, the preview demonstrates the filter's effect on a placeholder box rather than your actual intended image -- upload a real file to see the blur applied specifically to that image's content.
Why this is CSS, not a pixel-level image edit
CSS filter only. Pixel-accurate canvas blur still belongs in an image editor. This generates a live CSS filter that blurs however the browser renders the image at that moment -- it doesn't modify or export a new, permanently blurred version of the actual image file. If you need a real blurred image file (for downloading, further editing, or a context where CSS isn't available), that requires an actual image editor or a canvas-based pixel manipulation tool instead.
CSS blur applied this way is fully live and adjustable in the browser -- change the blur value and every instance of that CSS updates instantly, unlike a pre-baked blurred image file, which would need to be regenerated from the original source each time you wanted a different blur amount.
A common real-world use for this technique is a blurred background image behind readable foreground text or a modal -- the blur helps the background recede visually and improves foreground text legibility without needing a separate, pre-blurred image asset.
Related CSS filter and image-processing tools
For a broader set of CSS filter functions (sepia, grayscale, blur combined) rather than blur in isolation, the CSS Filter Generator covers that fuller combination.
For actually adding a watermark overlay on top of an image (a related compositing task), the Canvas Watermark Overlay Tool is a related but distinct image-treatment tool.
Frequently Asked Questions (FAQ)
Why does the preview show a generic box instead of my actual image?
Without an uploaded file, the tool demonstrates the CSS filter effect on a placeholder preview box. Upload a real image file to see the blur filter applied specifically to that image's content instead of the generic placeholder.
Does this tool create a new, permanently blurred image file?
No. CSS filter only. Pixel-accurate canvas blur still belongs in an image editor. It generates a live CSS filter that blurs the image as rendered by the browser. It doesn't modify or export a separate blurred version of the actual image file -- that would require an image editor or a canvas-based pixel manipulation tool instead.
Can I adjust the blur amount dynamically after applying this CSS?
Yes -- since it's a live CSS filter rather than a pre-baked image, changing the blur pixel value updates the effect instantly everywhere that CSS is applied, without needing to regenerate any image file.
What's a common practical use for a blurred background like this?
Placing readable foreground text or a modal dialog over a blurred background image -- the blur helps the background visually recede and improves the legibility of foreground content, without needing a separate pre-blurred image asset.
Is CSS blur the same as the blur applied in an image editor like Photoshop?
CSS filter only. Pixel-accurate canvas blur still belongs in an image editor. Conceptually similar but not identical -- CSS blur is a live, browser-rendered visual effect, not a pixel-level transformation of the actual image data. For pixel-accurate blur baked permanently into an image file, a dedicated image editor or canvas-based tool is more appropriate.
