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PDF to Black & White (Grayscale)

Convert every page to shades of grey. Free, and runs entirely in your browser — nothing you enter is uploaded, stored or sent to a server.

About PDF to Greyscale

Every page converted to shades of grey. The usual reasons are printing on a monochrome printer without letting the driver make its own decisions, saving colour ink, and preparing a document for a photocopier.

Grey is computed by luminance rather than by averaging the three channels, which sounds pedantic and is visible. The eye is roughly twice as sensitive to green as to red and nearly ten times as sensitive as it is to blue; averaging ignores that, so a red heading comes out the same grey as a blue one and both come out too light. Weighting them the way the eye does keeps the relationships between colours intact.

As with everything here that changes appearance, the pages are rendered and rebuilt as images — the text stops being text, and the file usually grows.

Where it helps

  • Luminance-weighted, so the relationship between colours survives the conversion.
  • The JPEG quality is yours to set, which is where the file size actually comes from.
  • Converting here rather than at the printer means what you see is what prints.
  • The document never leaves your browser.

Limits

  • The text becomes an image and can no longer be searched or selected.
  • It is not the same as a true monochrome PDF: the result is a colour-space image that happens to be grey, not a one-bit or DeviceGray document.
  • A printer may still apply its own conversion on top unless it is told the document is already grey.
  • Links, bookmarks and form fields do not survive.
  • Fine coloured detail — a pale highlight over text — can disappear entirely once the hue is gone.

Frequently asked questions

Why not let the printer do it?

You can, and for a simple document it is fine. Converting here means you see the result first and it is the same on every printer — driver conversions vary, and most of them average the channels, which flattens the differences between colours.

Will this make the file smaller?

Often, but not always. Grey JPEG data compresses better than colour, and against that the whole document has been re-rendered as images. A text document usually gets larger; a colour scan usually gets smaller.

Is this a true black-and-white PDF?

No. It is grey imagery in a normal PDF. A genuinely one-bit document — the kind a fax or an archival scan produces — needs a bitonal encoder, which a browser does not have.

Where did my highlights go?

A pale yellow highlight and white paper are nearly the same luminance, so in grey they are the same shade. That is correct, and it is why highlighting is a poor choice for a document that may be printed in grey.

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