
calibre
Amazon Kindle
Cool Reader
Google Play Books
Sumatra PDF
Okular
Librera Reader
FBReader is an e-book reader for various platforms. Features:

Keygen
The simplest way to license your app.

Which is more popular?
Based on our record, FBReader should be more popular than Keylight.dev. It has been mentioned 10 times since March 2021.
Website, pricing, platforms and company facts side by side.
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| Website | fbreader.org | keylight.dev |
| Pricing | — | |
| Platforms | — | |
| Company | — | Startup from Belgium · 1 - 9 employees · 2026 |
| Listed in |
In their own words, as submitted to SaaSHub.


No description of FBReader yet.
Keylight sits between your payment provider and your app. Licenses, activations, customers, and usage all live here. Switch providers, or run several, without shipping a new build.
What each product offers, as listed by its team.


Possible disadvantages
An editorial look at what each product does well and who it suits.


Overall verdict
Why this product is good
Recommended for
FBReader is recommended for readers who value customization in their reading experience and need support for various e-book formats. It's ideal for those who read on multiple devices and platforms, as it offers sync features and wide compatibility.
Overall verdict
Why this product is good
Recommended for
Walkthroughs and reviews on video.
Review FBReader on Linux Ubuntu
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How often each product is chosen within a category, 0–100% relative to the other.


As answered by people managing FBReader and Keylight.dev.
Keylight.dev's answer:
Keylight keeps app licensing separate from payments. You can use Stripe, Paddle, Lemon Squeezy, Polar, Gumroad, or your own checkout without tying your app to one provider.
It handles license keys, device activations, trials, free tiers, offline access, grace periods, and signed license state through one SDK.
Keylight.dev's answer:
My goal is to make all apps work with Keylight. So all of your licenses, from any types of apps, is going through Keylight for analytics, customer portal, support, ...
Most licensing tools are bundled into a payment provider. Keylight is built as an independent licensing layer.
That means you can change payment providers, sell through multiple platforms, or change your pricing model without rebuilding licensing inside your app.
It also gives developers a ready-made SDK and dashboard instead of requiring them to build and maintain their own licensing backend.
Keylight.dev's answer:
Keylight is primarily built for independent developers and software companies selling apps directly to customers.
Its main audience includes:
macOS and iOS developers Web app and SaaS developers Developers selling outside app stores Teams migrating from a payment provider’s built-in licensing Developers who need trials, device limits, offline access, and license analytics
Keylight.dev's answer:
Keylight started because I kept rebuilding the same licensing systems for different apps: license keys, trials, activations, offline access, device changes, and all the edge cases that come with them.
I also did not want licensing to be controlled by whichever payment provider an app happened to use.
So I built Keylight as a standalone layer between the app and the payment provider. Payment platforms send events to Keylight, and the app receives one consistent license state through the SDK.
Keylight.dev's answer:
That's confidential.
Keylight.dev's answer:
Swift and Swift Package Manager for the Apple SDK Rust SDK / JS SDK / C# SDK / C++ SDK TypeScript React Next.js Stripe Connect and payment-provider webhooks Cryptographic signatures for secure, offline-capable licenses REST APIs for application and provider integrations
Share your experience with using FBReader and Keylight.dev. For example, how are they different and which one is better?
External articles and on-site reviews we used to compare the two products.


FBReader is a lightweight, multi-platform ebook reader, free but not open-source, supporting various formats like ePub, fb2, mobi, rtf, html etc. It includes access to popular network libraries from where you can...
The Favorite Book Reader (FBReader) is a free app that used to be open source. As such, it used to be available for a multitude of devices but now caters to iOS and Android users. There’s also a beta version in...
Recommendations tracked on public social media and blogs since March 2021.


I use fbreader, it's probably in your disto's repository or you can get in from fbreader.org. Source: over 3 years ago
I've been using FBreader for years, and it can use the built in Android TTS. https://fbreader.org/. Source: almost 4 years ago
Based on what's on ZLibrary, various formats, though principally PDF, ePub, Mobi (Kindle), DJVU (similar to PDF), FB2, and a few others. Most ebook readers (with the exception of Amazon's own Kindle reader) can read virtually all of... - Source: Hacker News / almost 4 years ago
You don't want to hand-roll Ed25519 and lease parsing. Most licensing SDKs hide this behind a couple of calls. With Keylight, for example, the offline path collapses to: activate once, then a local checkOnLaunch() that verifies the lease... - Source: dev.to / 3 months ago
Full disclosure: I now build Keylight, so weigh this accordingly — I'm telling you the seam it's designed for, not that it wins every row. - Source: dev.to / 3 months ago
Full docs and the free tier are at keylight.dev. If you're on Tauri or Electron instead of native Swift, the same SDK pattern exists in JS/Rust. - Source: dev.to / 3 months ago
When comparing FBReader and Keylight.dev, you can also consider the following products.


A dead-simple software licensing API built for developers
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Amazon Kindle software lets you read ebooks on your Kindle, iPhone, iPad, PC, Mac, BlackBerry, and...
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Fast and small cross-platform eBook reader for desktops and handheld devices
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Google Play Books lets you search, preview, and buy millions of books using Google Book Search.
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Sumatra PDF is a slim PDF/DjVu/EPUB/XPS/CHM/CBR/CBZ/MOBI viewer for Windows.
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