Is this the same as desaturate in Photoshop?

Close enough for web. It is the browser grayscale filter, not a lab-grade channel mix.

Can I keep one color?

Not here. That is a selective-color job for an editor.

Drop an image

Or click to browse. The file stays in this tab.

Choose file

CSS-style grayscale on the canvas, then export. Soft-focus instead is blur image. Flattening a gray PNG to JPEG is PNG to JPG.

Is this the same as desaturate in Photoshop?: Close enough for web. It is the browser grayscale filter, not a lab-grade channel mix.
Can I keep one color?: Not here. That is a selective-color job for an editor.

Image resizer

Resize by pixels, percent, or longest side. JPEG, PNG, or WebP out.

JPG compressor

Shrink JPEGs with a quality slider. Stays in your browser.

PNG compressor

Reduce PNG size by scaling or converting to WebP or JPG.