PDF Dark converts any PDF into a permanent dark-mode file you can download, share, and reopen in any viewer — all within your browser, with no uploads.
What is PDF Dark?
PDF Dark is a free, open-source (MIT) web app that converts standard PDF files into dark-mode PDFs. It takes a PDF (up to 50 MB), applies a saturation-based inversion algorithm that preserves photos and charts while darkening backgrounds and text, and outputs a new PDF with the dark theme baked into the file itself — not a viewer toggle. Everything runs locally via a Web Worker; no file ever leaves your device.
Key Features
- 100% browser-side conversion — The entire process runs in your browser via a Web Worker. No file upload, no signup, no install.
- Four dark themes — Choose Midnight (near-black), Sepia (warm tint), Solarized (low-contrast blue/green), or OLED Pure Black (#000 background) for maximum contrast on OLED screens.
- Download the darkened PDF — Save the converted file as a standard PDF that stays dark in any reader: Chrome, Firefox, Safari, Edge, Acrobat, Kindle, iPad, Preview.
- Read in-browser before saving — Preview the darkened file page by page right on the site, then decide whether to download.
- Works on mobile — iOS Safari and other mobile browsers can drop/upload PDFs directly; no app install required.
- Saturation-based algorithm — Photos and charts retain their original colors while text and white backgrounds are inverted, preventing washed-out images.
- Handles scanned PDFs — Each page is rendered as an image and inverted uniformly, so handwriting, yellowed scans, and old documents become light-on-dark automatically.
- Free and open source — MIT-licensed, no ads, no signup, no server-side processing.
Who should use PDF Dark?
- Night readers — People who read PDFs in low-light environments and want to reduce eye strain without installing browser extensions that only fake a dark theme.
- Students with late-night research — Convert research papers or textbook PDFs into a permanent dark-mode file that stays dark when reopened on a phone, tablet, or laptop.
- Developers reading code-heavy documents — Invert code PDFs and technical documentation to a low-light theme that is easier on the eyes under bright office lights or in dark rooms.
- OLED phone users — Use the OLED Pure Black theme to extend battery life when reading long PDFs on AMOLED screens.
Use cases
- Read PDFs at night without eye strain — Drop a bright PDF, pick the OLED or Midnight theme, and read directly in the browser. The dark background eliminates the white glare.
- Share a dark-mode PDF — Convert a PDF and download it; the dark theme is baked into the file, so recipients see it dark in any viewer.
- Darken scanned PDFs — Old, yellowed scanned documents are normalized to a dark background, making text readable without the original page discoloration.
How does PDF Dark work?
- Drop or click to upload a PDF (up to 50 MB).
- Pick one of four themes: Midnight, Sepia, Solarized, or OLED.
- Read the darkened PDF in-browser, or click download to save the file as a new dark-mode PDF.
Pricing
PDF Dark is free and MIT-licensed. No signup, no ads, no paid tiers.
FAQ
Is my PDF uploaded to your server?
No. PDF Dark runs 100% in your browser. We have no server that receives your file — the conversion happens locally.
How is this different from a browser dark-mode extension?
Extensions only restyle the PDF while it's open in that browser tab. Close the tab or share the file, and it reverts to white. PDF Dark rewrites the actual PDF file, so the dark theme persists in every viewer — Chrome, Firefox, Safari, Acrobat, Kindle, iPad.
Does it work on iPhone or iPad?
Yes. Safari on iOS can upload PDFs directly to this page. No app install is needed.
