Grayscale Image Converter
Convert one photo or several at once to grayscale using the correct relative-luminance formula (not a naive color average) — all done entirely in your browser via Canvas, with nothing ever uploaded to a server.
Your images are processed on your device via Canvas and are never uploaded to our servers.
Drag images here or choose them
You can select multiple images at once (JPG, PNG, or WebP)
What this tool does
Converts images to greyscale, replacing each pixel's colour with a single brightness value. Several images can be converted at once.
When to use it
- A document or image is going to a monochrome printer and you want to see the result first.
- A design needs a consistent look with the distraction of colour removed.
- Archive images that should share one visual treatment.
- You are testing whether a design still reads without relying on colour to carry meaning.
How to use it
- Drag your images onto the drop area or choose them.
- Wait for the conversion to finish.
- Download the greyscale images individually or with "Download all as ZIP".
A practical example
Input
A colour product photo against a bright background.
Output
The same photo in shades of grey, at the same dimensions and detail, with colour distinctions gone.
Limitations
- The change cannot be undone in the output file — colour information is not recoverable from it, so keep the original.
- Elements distinguished only by colour become indistinguishable, which is exactly what makes this useful as an accessibility check.
- Supported formats are JPG, PNG and WebP.
Privacy and processing
The conversion happens inside your browser through the canvas and no image is uploaded.
Technical notes
- The grey value is a weighted average of the three channels reflecting the eye's greater sensitivity to green than to red or blue, rather than a plain arithmetic mean.