head to head · open source
koreader vs substance
koreader has 30,818 GitHub stars, 2,019 forks, 1,345 open issues and last shipped yesterday. substance has 2,738 stars, 121 forks, 41 open issues and last shipped 7 months ago. koreader leads on adoption by 1,026% (30,818 vs 2,738 stars). koreader is written in Lua under AGPL-3.0; substance is written in JavaScript under MIT. koreader has attracted 7% as many forks as stars, substance 4%. koreader was the more recently maintained of the two, and both are self-hostable with no licence fee.
Two open source projects, one decision. Both are free and self-hostable — the differences are community size, license terms, language stack and release pace.
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Side by side
| koreader | substance | |
|---|---|---|
| GitHub stars | ★ 31K | ★ 2.7K |
| License | AGPL-3.0 | MIT |
| Written in | Lua | JavaScript |
| Last push | 2026-11-02 | 2026-04-02 |
| Forks | ⑂ 2.0K | ⑂ 121 |
| Self-hosting | Yes | Yes |
| Data ownership | Your server | Your server |
pick koreader if
- You weight community size — 31K stars and counting
- You want the AGPL-3.0 license terms
- Your stack matches Lua
- You value the larger contributor base for long-term maintenance
pick substance if
- You want the substance feature set and don't need the biggest community
- You prefer the MIT license terms
- Your stack matches JavaScript
- You evaluated both and substance fits your workflow better
About koreader
KOReader is a document viewer primarily aimed at e ink readers. [![AGPL Licence][badge license]](COPYING) [![Latest release][badge release]][link gh releases] [![Gitter][badge gitter]][link gitter] [![Mobileread][badge mobileread]][link forum] [![Build Status][badge circleci]][link circleci] [![Coverage Status][badge coverage]][link coverage] [![Weblate Status][badge weblate]][link weblate] Download • User guide • Wiki • Developer docs Main features portable : runs on embedded devices (Cervantes, Kindle, Kobo, PocketBook, reMarkable), Android and Linux computers. Developers can run a KOReader emulator in Linux…
read the full koreader overview →
About substance
Substance.js Substance is a JavaScript library for web based content editing. It provides building blocks for realizing custom text editors and web based publishing system. It is developed to power our online editing platform Substance. Development Install the dev dependencies. Run the dev server. Navigate to for the running the browser test suite. The test suite is rebuilt as you make changes to the source files. To run the test suite headless.
read the full substance overview →
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Frequently asked questions
Is koreader or substance more popular?
koreader has 30,818 GitHub stars and substance has 2,738. koreader has the larger community by that measure.
Are koreader and substance free?
Both are open source. koreader is licensed under AGPL-3.0 and substance under MIT. Neither carries a licence fee.
What is the difference between koreader and substance?
koreader is written in Lua and substance in JavaScript. The practical differences are community size, licence terms, language stack and release cadence — all compared in the table above.
Which should I choose, koreader or substance?
Choose koreader if you want the larger community (30,818 stars) or its AGPL-3.0 licence terms. Choose substance if its feature set, stack or MIT licence fits better. Both are self-hostable.