Will this reduce my PDF's file size?

Usually, yes — grayscale images compress better than color ones. But because every page is rasterized into an image, a mostly-text PDF can end up larger than the original. Lower the DPI or quality if size matters more than sharpness.

What grayscale formula does this tool use?

We use the perceptual luminance formula (0.2126×Red + 0.7152×Green + 0.0722×Blue), the same weighting used by video standards, rather than a flat average — it produces grays that match how the human eye perceives brightness.

Is my PDF uploaded to a server?

No. Everything happens locally in your browser using JavaScript — your file is never uploaded anywhere.

Will my text still be selectable?

No. Converting to grayscale requires rasterizing every page into an image, so the output PDF has no selectable text layer — it's effectively a scanned-looking document. If you need to keep selectable text, this isn't the right tool for you.

What's a good DPI to choose?

150 DPI is a good balance for on-screen viewing and everyday printing. Use 300 DPI for documents with fine print or detailed images, or 100 DPI to keep file size as small as possible.

Why did my file get bigger?

Rasterizing a page turns crisp vector text into a full-page image, which usually takes more bytes than the original text and font data — especially for text-heavy documents with little color to begin with. Try a lower DPI or JPEG quality to bring the size back down.