Sumatra PDF vs Shadow Reader: Best PDF Reader for Dark Mode in 2025?
As more students, researchers, and night owls turn to digital documents, the demand for a clean, dark mode PDF reading experience has skyrocketed. Two contenders stand out for different reasons: Sumatra PDF, a legendary minimalist reader known for its speed, and Shadow Reader, a modern tool built specifically for focused reading in dark mode. In this post, we'll compare both, especially for those who read long documents, highlight heavily, and work late into the night.
Quick Comparison
| Feature | Sumatra PDF | Shadow Reader |
|---|---|---|
| Dark Mode | Inverts colors but background and toolbar remain the same | Both files and the UI blend in the dark |
| Annotations | Offers highlights, comments, and other basic annotations | Offers highlights and also |
| Note-Taking | N/A | Side by side note taking with files |
| Design | Outdated | Modern and minimalist |
| Platform | Windows only | Web |
| Performance | Small install size, blazing fast performance | Loads large PDFs immediately |
Sumatra PDF Overview
Sumatra PDF has been a favorite among power users, developers, and minimalists for over a decade. It's an open-source, Windows-only PDF reader designed with one core principle: simplicity above all else.
If speed and minimalism are your top priorities, Sumatra delivers. It launches almost instantly, takes up barely any system resources, and doesn't try to do too much. It's the kind of tool that gets out of your way - perfect for quick document previews or reading plain PDFs without distractions.
✅ Strengths
- Blazing fast performance: It opens PDFs in a fraction of a second, even on older machines.
- Tiny install size: At under 10MB, it's one of the lightest PDF readers available.
- No clutter: The interface is as bare-bones as it gets. No ribbons, sidebars, or popup menus.
- Open source: Actively maintained by a strong community of developers.
⚠️ Weaknesses
- Sumatra has a dark mode option for PDFs, but the UI around it stays light
- Basic annotation support: Sumatra now supports text highlights and simple annotation editing, but it's minimal and not well-suited for intensive academic or research workflows.
- Dated UI: The interface hasn't changed much since the early 2010s. It works, but it doesn't feel modern.
- Windows-only: There's no native support for macOS, Linux, or mobile platforms.
Sumatra is excellent if you just want to view PDFs quickly. But if you're a student, researcher, or heavy reader who needs to interact with your documents through highlights, notes, or annotations, you'll likely find it lacking.
Shadow Reader Overview
Shadow Reader is a modern, web-based PDF reader designed from the ground up for deep, focused reading, especially for late night sessions. Originally built to solve a personal pain point (reading dense PDFs late at night without getting blinded), it's evolved into a tool aimed at students, researchers, and anyone who needs to engage seriously with their reading material.
Where Sumatra aims for speed and simplicity, Shadow Reader focuses on comfort, ergonomics, and cognitive workflow. It's not just about viewing PDFs, it's about thinking through them.
✅ Strengths
- Quality dark mode: Designed with a dark UI from the start for clean, eye-friendly reading. Shadow Readers dark mode applies not only to the PDF but to the entire UI and reading experience.
- Highlighting & annotation: Mark up your documents directly with highlights, and markers. Advanced annotation features are on the roadmap too.
- Side-by-side note-taking: Take structured notes right next to your reading, without switching tabs or losing focus. Shadow Reader is built for extracting knowledge from files.
- Modern UI/UX: Built for clarity and flow, with an interface that fades into the background as you read.
- Cross-platform access: Since it's web-based, it works on Windows, macOS, Linux, and mobile, no installation needed.
⚠️ Limitations
- Web-first: Shadow Reader currently requires an internet connection, though offline mode is on the roadmap.
- Still evolving: As a newer tool, it's under active development. Some features like EPUB/web article support and AI synthesis are not yet live but planned.
- Smaller ecosystem: Unlike legacy readers, it doesn't yet have plugins, extensions, or deep integration with citation tools (though markdown export is possible).
While Sumatra is ideal for users who want to open and close a PDF fast, Shadow Reader is made for those who want to go deep, engage critically, and retain what they read. If your reading involves comprehension, synthesis, and output, Shadow Reader offers the structure to support that workflow.
Final Verdict
If your goal is simply to open PDFs quickly with minimal fuss, Sumatra PDF remains a solid choice. It's blazing fast, lightweight, and ideal for users who don't need much beyond basic viewing and the occasional highlight.
But if you're someone who reads to think, remember, and produce, whether you're a student tackling dense readings, a researcher annotating papers, or a night owl trying not to fry your retinas then Shadow Reader is built for you.
It goes beyond passive reading to support active engagement with your documents:
- Native dark mode that actually works.
- Highlighting and structured note-taking.
- A modern interface that supports long sessions without distraction.