Grayscale Image

Convert an image to black and white by the method you choose, at the strength you choose, without uploading it.

Runs on your deviceImagesWorkingNo account needed

What this tool does

Grayscale Image works out one grey value for every pixel and writes that value back into all three colour channels. Luminance, the default, weights the channels the way the eye does — 0.2126 red, 0.7152 green, 0.0722 blue, the Rec. 709 figures — so a pure red arrives at 54 out of 255 rather than at mid-grey. Average treats the three equally. Lightness takes the midpoint between the brightest and the darkest channel, which sends a saturated red and a saturated green to the same 128 even though luminance puts them 128 levels apart, so the result is flatter.

The Red, Green and Blue options do something else entirely: each keeps one channel and discards the other two, which is the digital form of the coloured filters black-and-white photographers screwed onto the lens. Red darkens a blue sky and smooths skin tones; blue lifts the sky and exaggerates blemishes; green falls between them and is close to how foliage reads. The cost is real, because a third of the captured data is now doing all the work — noise in that single channel is no longer averaged against the other two, so a high-ISO frame looks grainier through a channel filter than it does under luminance.

Strength runs from 1 to 100 per cent and blends the grey back towards the original colour, so 40 per cent leaves a muted, partly desaturated picture rather than a neutral one. It cannot be set to zero, since a run that changed nothing would hand back a re-encoded copy of your file. The alpha byte of every pixel is left exactly as it was, so transparency comes through into PNG, WebP and AVIF output; JPG has no alpha, so picking it fills the transparent areas with white before any conversion happens. Nothing is resized or cropped either, and the work all happens in this browser tab — the file is read from your disk into memory, gone over in slices of about a quarter of a million pixels so the page stays responsive, and never sent anywhere.

Three limits are worth knowing before you convert anything you care about. The output is an ordinary colour file whose pixels happen to be neutral, not a single-channel greyscale image — the canvas hands the encoder RGBA — so a PNG still carries a full colour value for every pixel and the drop in file size is smaller than the loss of colour suggests. This is greyscale rather than bitonal: pixels keep the full range of levels between black and white, so it is the wrong tool for a 1-bit fax-style scan. And the picture is decoded to raw pixels and re-encoded, which discards EXIF, GPS tags and any embedded colour profile, and spends one generation of encoder loss whenever you write JPG, WebP or AVIF.

How to use it

  1. Add your images. Drop in JPG, PNG, WebP, GIF, BMP or SVG files; AVIF decodes on a recent browser. Queue several at once and each is converted in turn on the settings you pick.
  2. Choose the method. Luminance unless you have a reason to deviate. Average and Lightness change the tonal balance; Red, Green and Blue are the single-channel photographic filters.
  3. Set the strength. 100 per cent is fully neutral. Lower values keep a trace of the original colour, which is what you want for a background image sitting behind text.
  4. Pick the output format and download. Stay with the input format — GIF, BMP and SVG fall back to PNG, the nearest thing the canvas can write — or force JPG, PNG, WebP or AVIF. The quality slider opens at 88 and is ignored unless the output is lossy. Downloads carry -bw on the end of the filename.

Processing & privacy

Runs on your device. Your file is processed directly in this browser.

Common use cases

Rescuing a shot with a bad colour cast

An orange tungsten cast or a green fluorescent one is a colour problem, and removing colour removes it outright. Often quicker than fighting the white balance.

Matching photos taken in different light

A set shot across a morning and an afternoon never quite agrees on colour. Converted to grey, only exposure differs, and that is far easier to even out.

Toning down a background image

Text over a busy photo competes for attention. Dropping the strength to 30 or 40 per cent mutes the picture without flattening it to a grey slab.

Emulating a red-filter landscape

The Red channel option darkens blue sky and lifts cloud edges, which is the look film photographers bought a physical red filter to get.

Preparing art for single-colour printing

Screen printing, laser output and mono photocopying all reduce to tone anyway. Converting first shows what will actually come off the press.

Questions

Are my images uploaded?
No. Decoding, desaturating and re-encoding all happen in this tab through the browser's own canvas, which is why the tool carries on working with the network switched off. The file is never transmitted or stored.
Which method should I pick?
Luminance for almost everything — it is the one that matches how bright each colour actually looks, so nothing changes its apparent weight in the frame. Average and Lightness are worth trying when luminance leaves a subject too dark. The channel options are creative choices, not corrections.
Why is the black and white file not much smaller?
Because it is still an RGB file. The three channels now hold identical values, which compresses somewhat better, but the encoder is not writing a single-channel greyscale image and there is no setting here that makes it. Expect a modest saving on PNG and a larger one on JPG, not a two-thirds cut.
Can I keep one colour and grey out the rest?
No. The conversion runs over every pixel, and there is no selection, mask or colour-range control, so the colour-splash effect is not available here. That needs a layer-based editor.
Can I get the colour back afterwards?
Not from the output. Three channels have been collapsed into one value and the original numbers are gone, so keep the source file. Strengths below 100 per cent still hold some of the original colour, but nothing here will put it back.
Is the animation kept when I convert a GIF?
No. Only the first frame is decoded, and GIF is not one of the output formats offered here, so an animation comes back as a single still named with -bw. Run it through GIF Splitter first if the movement matters.
Why did my transparent background turn white?
Because you chose JPG, which has no alpha channel, so transparent pixels are painted white before the conversion runs. This tool offers no background colour of its own — pick PNG, WebP or AVIF to keep the transparency instead.

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