PDF Dark is a free, open-source web application that converts any PDF document into a true dark-mode version you can download, share, and reread on any device. The entire conversion happens locally in your browser — your file never touches a remote server. Anyone can verify this client-side behavior by opening the browser DevTools network panel during conversion. There is no upload, no signup, and no tracking.
What it does
PDF Dark inverts and recolors the text, vector graphics, and backgrounds of a PDF so that it becomes comfortable to read in low-light environments. Unlike a viewer-level dark-mode toggle, the output is a real PDF file with darkness baked in. That means the file stays dark when opened on a Kindle, an iPad, in Adobe Acrobat, on a Linux desktop, or anywhere else. A saturation-based algorithm preserves photographs, charts, and diagrams in their original colors so that figures in research papers and product manuals remain understandable.
Who it is for
Night readers, students, researchers, writers, and accessibility users who experience eye strain from reading bright PDFs in dim rooms or on bright phone screens. PDF Dark is also a fit for privacy-conscious users who refuse to upload sensitive documents to commercial PDF cloud converters. The output is a standard, portable PDF, so it integrates naturally into existing reading workflows.
Pricing and access
PDF Dark is 100% free. There is no premium tier, no subscription, and no metered usage. The source code is MIT-licensed and openly published on GitHub, which means individuals and teams can self-host their own instance or audit the code line by line. The hosted version at pdfdark.org imposes no usage limits and runs entirely in the visitor's browser.
Key features
- Fully client-side: every byte of the PDF stays on your device
- Photo-aware darkening: pictures keep original colors while text and backgrounds invert
- Real PDF output: not a viewer toggle, the darkness is baked into the file
- Cross-platform output: works in Kindle, iPad, Acrobat, mobile, and any standard PDF reader
- MIT-licensed open source: clone, modify, self-host, or audit on GitHub
- No upload, no signup, no ads, no analytics on the conversion path
Quick answers
Does PDF Dark work on iPhone or Android? Yes — it runs in mobile Safari and Chrome with no install.
Is my file uploaded? No, conversion runs entirely in your browser; DevTools confirms zero outbound bytes for the PDF.
Is PDF Dark free forever? Yes, and the source code is open under MIT so any future change is verifiable.
Does it work on scanned PDFs? Yes, scanned pages are processed as images with the photo-aware algorithm.
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