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PDF to Black & White

Local

Convert PDF to a true 1-bit black and white (bitonal) document

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B&W PDF
Local
Processing limits
  • Rendered PDFs: up to 500 pages, 8,192 px per side, 32 MP per page, 100 MP in total, and 250 MiB of output.
  • These are memory budgets, not upload limits — a large file is only ever read by your own browser.
Tool Details
Input formatsPDF
Output formatPDF
Max file size100 MB
Max files1
PDF render limits

500 pages · 8,192 px/side · 32 MP/page · 100 MP total · 250 MiB output

ProcessingLocal
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Privacy First

Your files are processed entirely in your browser. Nothing is uploaded to any server.

How do I convert a PDF to 1-bit black and white?

Open the PDF, pick a resolution, choose a hard threshold or one of three dithering modes, and convert. Each page is rendered, reduced to one bit per pixel, and written back as a DeviceGray image with BitsPerComponent 1 — a genuinely bitonal document, not a two-tone picture still stored at 24 bits per pixel. Pages become flattened images, so text stops being selectable. Everything runs in this browser tab.

About the PDF to Black & White

Convert each PDF page into a genuine 1-bit bitonal image — one bit per pixel, DeviceGray with BitsPerComponent 1, Flate-compressed — rather than a two-tone picture still stored at 24 bits per pixel. Choose the render resolution, the brightness threshold, and whether to use a hard threshold or Floyd-Steinberg, Atkinson or ordered dithering. Output pages are flattened images, so text and form fields are no longer selectable or editable.

  • Produce a genuine 1-bit (bitonal) PDF for fax, microfilm, cheque imaging or a records system that rejects grayscale and colour input.
  • Collapse the size of a scanned document, because one bit per pixel stores a page in an eighth of the space that 8-bit gray needs before compression.
  • Rescue a grey, unevenly lit phone scan by pushing the threshold until the text is solid black on clean white.
  • Keep photographs legible in two tones by choosing Floyd-Steinberg, Atkinson or ordered dithering instead of a hard threshold.

How to use the B&W PDF tool

  1. 1

    Upload PDF file

    Select PDF file from your device or drag file into the upload area.

  2. 2

    Choose settings

    Choose settings such as Resolution, Dithering, Threshold before processing.

  3. 3

    Convert to PDF

    Run the B&W PDF tool to create the PDF output.

  4. 4

    Download the result

    Download the finished file. The original file stays on your device and is not uploaded.

What is the difference between 1-bit, bitonal, monochrome and grayscale?

1-bit and bitonal mean the same thing: every pixel is stored in a single bit, so it is either ink or paper with nothing in between. Monochrome is looser — it only means one colour, and a grayscale scan is technically monochrome too. Grayscale keeps a full range of intermediate tones at 8 bits per pixel, so a photograph still looks like a photograph. The distinction matters because records systems, fax gateways and cheque-imaging pipelines that ask for "black and white" almost always mean 1-bit specifically, and will reject an 8-bit grayscale file that merely looks two-tone.

How much smaller does 1-bit output make a PDF?

Before compression, exactly one eighth the size of the same page at 8-bit grayscale and one twenty-fourth the size of 24-bit RGB, because that is the ratio of the bit depths. A 300 DPI Letter page is 8.4 million pixels, which is 1.05 MB of raw bitonal data against 25.2 MB as RGB. Flate compression then works unusually well on bitonal scans because long runs of identical white pixels collapse to almost nothing, so real-world text pages routinely land far below that raw figure. The tool reports the before and after sizes when it finishes rather than asking you to take the arithmetic on trust.

When should you dither instead of using a hard threshold?

Use a hard threshold for anything made of type and lines — scanned text, signed forms, engineering drawings — where a dither pattern would sit on top of the letterforms as noise and make small print harder to read. Switch to dithering when the page contains photographs or shading, because a threshold collapses a face into flat patches. Floyd-Steinberg diffuses the quantisation error into neighbouring pixels and gives the most natural grain; Atkinson passes on only three quarters of that error, which holds contrast better on faded scans; ordered 4x4 produces a regular cross-hatch that some print workflows prefer because it is predictable.

Is this the same as CCITT Group 4 fax encoding?

The pixels are, the compression is not. CCITT Group 4 is the run-length scheme fax machines and scanners use for bitonal images, and it also stores one bit per pixel — that shared lineage is why "1-bit" and "fax quality" get used interchangeably. This tool produces the same 1-bit pixel data but compresses it with Flate rather than Group 4, because Flate is available natively in the browser and Group 4 is not. Group 4 usually wins on clean scanned text; Flate often wins on dithered images. If you specifically need Group 4, render the PDF with Ghostscript to the tiffg4 device instead.

Are my files uploaded when converting a PDF to 1-bit black and white?

No. Every page is rendered, thresholded and bit-packed by code running in your browser. Bitonal conversion is usually applied to scanned paperwork on its way into an archive or a records system, and that paperwork tends to be the most sensitive material anyone handles — so the fact that the file never leaves the machine is the point, not a footnote.

How to do this offline, on the command line

For true bitonal output offline, render to a 1-bit device. tiffg4 is the fax-lineage encoder and usually produces the smallest files for scanned text.

Ghostscript

macOS: brew install ghostscript · Debian/Ubuntu: apt install ghostscript

gs -sDEVICE=tiffg4 -r300 -dNOPAUSE -dBATCH -sOutputFile=scan.tif scan.pdf

Produces a 1-bit CCITT Group 4 TIFF at 300 DPI. Use tiffscaled instead of tiffg4 with -dDITHERPPI to get a dithered result.

ImageMagick

macOS: brew install imagemagick · Debian/Ubuntu: apt install imagemagick

magick -density 300 scan.pdf -threshold 50% -monochrome bw.pdf

Delegates rendering to Ghostscript. Swap -threshold for -ordered-dither o4x4 to keep photographs legible.

Frequently Asked Questions

Is this a real 1-bit PDF, or just a picture that looks black and white?
A real one. Each page is written as a DeviceGray image XObject with BitsPerComponent 1, so the pixel data holds one bit per pixel. Open the output with qpdf --json or any PDF inspector and you will see /BitsPerComponent 1 rather than the 8 that an ordinary two-tone raster would report.
What is the difference between grayscale and 1-bit black & white?
Grayscale keeps many shades of gray at 8 bits per pixel, like a black-and-white photograph. 1-bit output stores one bit per pixel, so every pixel is ink or paper. That is what fax gateways, cheque imaging and microfilm archives mean when they ask for black and white, and it is why the file gets so much smaller.
Which dithering mode should I choose?
Hard threshold for text, forms and line art, where a dither pattern would sit on the letterforms as noise. Floyd-Steinberg for photographs, Atkinson when a faded scan needs the extra contrast, and ordered 4x4 when a downstream workflow expects a regular, predictable pattern.
Does it use CCITT Group 4 compression like a fax?
No. The pixel data is the same 1 bit per pixel a Group 4 fax uses, but it is compressed with Flate because that is what browsers provide natively. Group 4 normally wins on clean scanned text; Flate often wins on dithered images. For Group 4 specifically, render with Ghostscript to the tiffg4 device.
Will the text stay sharp?
Yes — dark text on a light background converts cleanly, and 200 or 300 DPI keeps small print legible. Because pages are re-rendered as images, the output text is not selectable, so keep the original if you need copyable text.
Is my document uploaded for processing?
No. Rendering, thresholding and bit-packing all run locally in your browser from start to finish.

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