Rhino Mod (1.21.4, 1.20.5) – Library for LatvianModder's Mods

Rhino is a library mod that provides a modern JavaScript engine for Minecraft, enabling script-based modding through KubeJS on Fabric, Forge, NeoForge, and Quilt mod loaders. Built as a fork of Mozilla's original Rhino JavaScript engine, it has been specifically modified to support ES6 syntax and replace the Nashorn engine that was removed in Java 15.

If you have ever tried to write custom scripts for Minecraft — tweaking recipes, modifying loot tables, or adding server-side automation — you have likely encountered KubeJS. What many players do not realize is that KubeJS depends entirely on a separate library to interpret JavaScript code within the game. That library is Rhino. With over 14 million downloads on Modrinth, Rhino has quietly become one of the most essential background dependencies in the Minecraft modding ecosystem. Developed by Lat under the KubeJS-Mods organization, it solves a critical compatibility problem: Java 15 and later versions removed the built-in Nashorn JavaScript engine, leaving mods that relied on scripting without a runtime. Rhino fills that gap with full ES6 support, ensuring that script-driven mods continue to function across modern Minecraft versions.

Key Features of Rhino

• ES6 JavaScript Support — Rhino brings modern JavaScript syntax to Minecraft modding, including arrow functions, template literals, destructuring, and let/const declarations. This means modpack developers can write cleaner, more readable scripts instead of being limited to outdated JavaScript standards.
• Java 15+ Compatibility — When Oracle removed the Nashorn engine in Java 15, it broke JavaScript-based modding tools. Rhino restores this functionality as a standalone library, so players running modern Java versions no longer face script execution errors or missing engine warnings.
• Multi-Loader Support — Rhino works across Fabric, Forge, NeoForge, and Quilt, making it one of the most versatile library mods available. Modpack creators who switch between loaders or maintain cross-platform packs do not need to worry about JavaScript compatibility breaking on a different loader.
• Lightweight Background Library — As a pure library mod, Rhino appears to be lightweight and does not add any visible in-game content, GUI elements, or world changes. It runs silently in the background, providing its JavaScript engine only when another mod — primarily KubeJS — calls upon it.
• Open Source Under MPL-2.0 — The entire codebase is available on GitHub under the Mozilla Public License 2.0, meaning the community can inspect, contribute to, and fork the project. This transparency gives modpack developers confidence that the library is safe and well-maintained.
• Active Maintenance Since 2022 — First published in May 2022 and last updated in October 2025, Rhino receives consistent updates to stay compatible with new Minecraft releases. This long maintenance track record reduces the risk of the library becoming abandoned mid-modpack development.
• Wide Version Coverage — Supporting Minecraft versions from 1.18.2 all the way to 1.21.4, Rhino covers a broad range of game versions. Whether you are maintaining a legacy 1.19.2 server or building a cutting-edge 1.21.4 modpack, the library has you covered.

Screenshots

How to Install Rhino

1. First, install your preferred mod loader. Rhino supports Fabric, Minecraft Forge, NeoForge, or Quilt — choose whichever matches your modpack setup.
2. Download the correct Rhino version for your Minecraft version and mod loader from the official Modrinth page. For example, if you play on Minecraft 1.21.4 with Fabric, download the Fabric build for 1.21.4.
3. Place the downloaded .jar file into your Minecraft mods folder. On most installations, this is located at .minecraft/mods/ in your game directory.
4. Install KubeJS or whichever mod requires Rhino as a dependency. Rhino does nothing on its own — it only activates when a dependent mod calls its JavaScript engine.
5. Launch Minecraft with your mod loader profile. If installed correctly, Rhino will appear in your mod list but will not produce any visible changes on its own.

Requirements & Compatibility

What's New

• Updated to support Minecraft 1.21.4 across Fabric, Forge, and NeoForge loaders.
• Continued ES6 compatibility improvements to align with the latest KubeJS scripting features.
• Expanded NeoForge support for newer Minecraft versions starting from 1.20.5 onward.
• Bug fixes and stability improvements for the JavaScript runtime under modern Java versions.
• Maintained backward compatibility with older Minecraft versions down to 1.18.2.

Pros and Cons

Alternatives to Rhino

• KubeJS — The primary mod that uses Rhino as its scripting engine, allowing players to customize recipes, events, and game mechanics with JavaScript. If you want Rhino's capabilities, KubeJS is the mod you actually interact with.
• CraftTweaker — A recipe and game customization mod that uses its own ZenScript language instead of JavaScript. A solid alternative for players who want script-based modding without needing a separate JavaScript engine.
• Architectury API — A cross-platform library mod that helps developers write mods compatible with multiple loaders. While it serves a different purpose than Rhino, it shares the same goal of enabling multi-loader mod development.

Download Rhino

Always download mods from official sources to stay safe.

Frequently Asked Questions

What does Rhino do in Minecraft?

Rhino provides a JavaScript engine that other mods use to run scripts inside Minecraft. On its own, Rhino adds no visible content or gameplay changes. It exists solely as a background library, primarily used by KubeJS to enable JavaScript-based modding such as custom recipes, event handling, and server automation.

Do I need to install Rhino manually?

It depends on your mod loader and launcher. Most modern mod launchers like CurseForge or Modrinth automatically download Rhino when you install KubeJS as a dependency. However, if you are manually managing your mods folder, you will need to download and place the Rhino .jar file yourself alongside KubeJS.

Is Rhino compatible with Fabric and Forge at the same time?

No — you need to download the correct version of Rhino for your specific mod loader. Rhino offers separate builds for Fabric, Forge, NeoForge, and Quilt. Using the wrong loader version will cause the mod to fail on startup, so always match the Rhino build to the loader you are running.

Will Rhino affect my game performance?

Rhino appears to be lightweight and should not noticeably affect performance during normal gameplay. It only activates when a dependent mod like KubeJS executes JavaScript code, so the engine is not running constantly. The actual performance impact depends on the complexity of the scripts you run through KubeJS rather than Rhino itself.

Does Rhino support Minecraft 1.20.5 on Fabric?

No — Rhino for Minecraft 1.20.5 is only available for NeoForge. Fabric support resumes in Minecraft 1.21 and later versions. If you need Fabric compatibility on an older version, consider using Minecraft 1.20.1, which supports both Fabric and Quilt alongside Forge.

You May Also Like

Hopper The Hedgehog Mod (1.21.11, 1.20.1) – Speeds Up Item Transfer

1 week ago

Better Ladders Mod (1.20.1) – Simplify Ladder Placement

1 week ago

AttributeFix Mod (1.21.11, 1.20.4) – Removes Arbitrary Limits

2 weeks ago

Bosses Delight Mod (1.20.1, 1.20) – Culinary Combat

2 weeks ago

Boss Music Mod (1.20.1) – Soundtracks That Play During Fights

1 week ago

My Nether's Delight Mod (1.21.11) – Nether for Farmer's Delight

1 week ago