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Image Grayscale Converter

Turn a colour photo into a proper luminance grayscale image in your browser, with a live preview and PNG, JPG or WebP output.

Choose a colour image

Grayscale result

The grayscale preview appears here.

Your file is never sent to a server. It is read and processed by your own browser, and the results are not stored.

How to use it

  1. Choose a JPG, PNG or WebP image.
  2. Preview the grayscale result and choose PNG, JPG or WebP.
  3. Download the new file. The original stays untouched.

Limits worth knowing

  • Colour is removed; tone and contrast are not changed.
  • JPEG output is lossy and flattens transparency onto white.
  • PNG and WebP keep transparency, subject to browser encoder support.
  • EXIF metadata is not copied into the output.
  • Images above 40 megapixels and files above 25 MB are refused.

Why luminance weights beat an average

Human vision is much more sensitive to green than to blue. A plain (R + G + B) / 3 average treats every channel as equally important, so a saturated blue sky can turn nearly black while a green leaf becomes mid-grey. The Rec. 709 weights follow perceived brightness instead.

The result is a grayscale image that preserves the tonal relationships a viewer expects, which is why the same formula is used in video and colour management.

A note on “black and white”

Grayscale is not the same as a one-bit black-and-white image. It keeps 256 levels of grey, so gradients, skin tones and shadows survive. If you need a true bitmap for print, that is a different conversion with a threshold or dithering step.

Frequently asked questions

Does Image Grayscale Converter upload my files to any server?

No. Image Grayscale Converter runs in your browser, and the file is read there rather than sent to a server for processing. Our host still sees ordinary page-request metadata, which is described on the privacy page.

Is Image Grayscale Converter free to use?

Yes, Image Grayscale Converter is free, with no paid tier, no account, and no watermark added to your output. The limits are technical rather than commercial: file size, page count and supported formats are listed on this page.

What file formats and sizes are supported?

Image Grayscale Converter supports .jpg, .jpeg, .png, .webp files up to 25MB directly in your browser.

Is this the same as turning saturation to zero?

Effectively, yes, but the arithmetic matters. This tool uses the Rec. 709 luminance weights (0.2126 red, 0.7152 green, 0.0722 blue), so bright greens do not become muddy dark grey the way a naive channel average would.

Does it keep transparency?

PNG and WebP keep the alpha channel. JPEG has no alpha, so transparent areas are flattened onto white.

Can I make the contrast stronger?

This tool changes colour, not tone. Use Brightness & Contrast after the grayscale conversion if you want a punchier black and white image.

Is the original changed?

No. The original file on your device is untouched. The tool produces a new download and reports its dimensions and size.