FernAPI
by Sunnit-M
FernAPI is a Fabric library for server owners that handles JSON-based permission data and the config files that go with it.
What it does
Server administrators who want permissions stored in readable JSON files can use FernAPI to load and manage that data. The library is still a work in progress, and the author lists a JSON-based permission API as unfinished work. Other mods can rely on it for the parts already present, such as starting and stopping a Fern server from within the server process.
Fern generates default config files when the server runs for the first time. Within config.json, the data type is chosen from a table, so the storage format can be adjusted without editing code. Parsing uses Jackson, and the author notes error handling as part of the codebase. Support for further data types is still pending.
FernAPI is server-side only, so players join without installing anything, and only the server needs the Fabric loader and the library. It is released under the MIT License and is open source, with the source code and an issue tracker published. Files exist for 1.21.10, with 0.5.1 as the latest build, dated 2026-02-04 on the beta channel.
Key features
JSON permission data
Permission data is held in JSON, a format that can be read and edited by hand.
Fern server control
The library can start a Fern server, stop it and start it again without restarting the whole process.
Default config generation
Default config files are written on the first run, so a server owner has a starting point to edit.
Data type selection
The data type used for storage is picked from a table listed in config.json.
Jackson-based parsing
Reading and writing JSON uses the Jackson library, and errors during these steps are handled by the library.
Compatibility
Latest build for each game version and loader.
Only full game releases are shown. This mod publishes no snapshot builds.
Use cases
Who it’s for: Server owners and developers of server-side mods on Fabric who want JSON-based permission and config handling. Players on a server running FernAPI do not need to install it.
How it compares
Data Command is also a Fabric, server-side only mod under the MIT License, but it targets 1.21.11 rather than 1.21.10. fabric-permissions-api covers 1.17.1 – 26.3 on Fabric with the same server-side environment and MIT License, so it reaches more versions. Fair Utils is Fabric-only for 1.21.5 under a Creative Commons non-commercial license and is not open source, and CookieLib is client-side only for 1.21.5 under All rights reserved.
| Mod | Loaders | Game versions | Environment | Updated |
|---|---|---|---|---|
| FernAPI | Fabric | 1.21.10 | Server-side only | 2026-02-04 |
| Data Command | Fabric | 1.21.11 | Server-side only | 2026-06-17 |
| fabric-permissions-api | Fabric | 1.17.1 – 26.3 | Server-side only | 2026-05-27 |
| Fair Utils | Fabric | 1.21.5 | Not published | 2025-06-07 |
| CookieLib | Fabric | 1.21.5 | Client-side only | 2025-08-09 |
Questions
Does FernAPI need to be installed on players' computers?
Which Minecraft version does FernAPI support?
Does FernAPI generate its own config files?
In the catalog
FernAPI is one of 3,514 Library mods on ModsFinder, and one of 2,348 Library mods for Fabric. 15,569 mods support Minecraft 1.21.10.
Similar mods
What the author says
And data does not port to new data type yet.
Official listing
- Modrinth page
- modrinth.com/mod/fernapi
- Owner
- Sunnit-M
- Published
- 2025-11-06
- Updated on Modrinth
- 2026-02-04
- Facts verified
- 2026-10-15