How to Read a PDF in Dark Mode (and Save Your Eyes)

PDFly guide · Updated October 2026

Most PDFs are bright white pages with black text. That is fine in daylight and tiring at night. A reading mode changes the colours on your screen without touching the file, so you can read comfortably at any hour. PDFly's PDF reading mode works in your browser and offers four looks.

The four modes

• Light: the PDF exactly as it was made.
• Sepia: a warm, paper-like tint that is softer than white. Good for long reading in a bright room.
• Dark: the colours are inverted with a softer contrast, so white paper becomes dark grey and black text becomes light.
• Night: a deeper, true-black version for reading in a dark room or on an OLED screen.

How to use it

1. Open Read PDF and drop your file on the page.
2. Choose a mode at the top. Press D to cycle through them.
3. Use + and − to zoom, or Fit width to fill the screen. The arrow keys move between pages.
4. Press Full screen for a distraction-free view.

The tool remembers the page where you stopped for each file, and the mode you chose, on that device. Open the same file later and you carry on where you left off.

Good to know

• The file is never changed. The colours only change on screen, so printing and downloading the original are unaffected.
• In dark and night modes, photos in the PDF are inverted too. If a picture matters, switch to light or sepia to see its true colours.
• Large documents open quickly because only the pages near the screen are drawn.
• Nothing is uploaded. Your PDF stays on your device.

Tips for comfortable reading

• Lower your screen brightness at night as well. Dark mode helps most when the screen is not blasting at full brightness.
• Pick sepia for hours of reading, dark for evenings, and night for a dark bedroom.
• Take a short break every 20 minutes and look at something far away.