filetity

IMAGE -> GRAYSCALE · Local tool

Grayscale image

Convert a colour image to black and white.

Last updated

  1. 01 / Your device

    the file stays here

  2. 02 / Browser memory

    the work runs locally

  3. 03 / Back to you

    saved on this device

When you would use this

Situations, not settings.

Printing where colour costs more
Converting first shows you what the print will look like, instead of leaving the conversion to a driver you cannot see.
A document that should look uniform
Scans from different sources carry different colour casts. Grayscale removes the mismatch.
Getting the tones right
Averaging the channels makes reds and blues collapse into the same grey. Luminance weighting keeps them apart, which is what this uses.

How it works / no cloud

A conversion engine, not an upload form.

filetity reads the pixels in your browser and replaces each one with its Rec. 709 luminance, which weights green far above red and blue because that is how human vision responds. Averaging the three channels instead is the common shortcut, and it renders bright green and deep blue as the same grey.

  • Offline ready
  • Installable app
  • No file limit queue

Straight answers

No accordion. Nothing hidden.

Is it free?
Yes, with no watermark and no page limit.
Does it need an account?
No. There is no account system.
Is my file processed on my device?
Yes. The file is read by your browser and never uploaded. There is no server to send it to.
What formats are supported?
JPG, PNG and WebP in. The same format out, so nothing else about the file changes.
What are the limits?
No image count limit. Very large images are bounded by the memory your browser gives a canvas.
Does it work on mobile?
Yes, on any modern mobile browser. Large files are limited by the memory the phone gives the browser.
Does it work offline?
Yes, after you have used it once. Your browser keeps what the tool needs, so it then works with no network connection.
Why do some black and white converters look flat?
Because they average the red, green and blue channels equally. To an eye, green is roughly five times brighter than blue, so an average renders a vivid green leaf and a deep blue sky as near-identical grey. This page uses the Rec. 709 weights that sRGB is defined against, which keeps the contrast that was actually there.
Is this the same as removing saturation?
Close, but not identical. Desaturating in some editors uses a different formula, often the midpoint between the lightest and darkest channel, which produces a flatter picture. Luminance weighting is the version that matches how the scene looked.
Can I get the colour back afterwards?
No. Converting to grey discards the colour information, so keep the original if you may want it. This tool never overwrites your file, it produces a new one.
Does transparency survive?
Yes. Only the red, green and blue values are replaced; the alpha channel is not touched, so a PNG with a clear background keeps it. A JPG has no alpha to begin with, so nothing changes there.
Can I do a batch?
Yes. Several images at once, each staying in its own format, delivered as a ZIP with -grayscale on each name. A JPG is re-encoded at quality 92 on the way out; a PNG is written exactly.

Keep working locally

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