Hydrogen
by CaffeineMC
Players who run heavily modded packs can use Hydrogen, a Fabric optimization mod that lowers the game's memory use through more compact data structures.
What it does
Hydrogen replaces parts of the game's block state and property storage with more compact data structures. The change matters most when other mods add many complex blocks, and it can still give smaller gains in lightly modded or vanilla play. Block model geometry is de-duplicated as well, which saves client memory when multi-part block models are in use.
The mod also repairs a few leaks in chunk loading, where NBT data read from disk stayed in memory after a chunk finished loading. Block model predicates are simplified and flattened to cut unnecessary chaining. Hydrogen is a Fabric mod for game versions 1.16.5 – 1.17.1 and is released under the GNU Lesser General Public License v3.0 only; its source code and issue tracker are public. The author has archived the project and will publish no further updates or support. Server installation brings little benefit at present, although the mod can run on a server alone, a client alone or both.
Key features
Compact block state storage
Block states and properties are kept in more compact structures, which reduces memory use when many complex blocks are loaded.
Shared block model geometry
Duplicate geometry in multi-part block models is merged, lowering client memory use.
Chunk loading leak fixes
NBT data is no longer retained in memory after its chunk has loaded from disk.
Flattened block model predicates
Predicate chains in block models are simplified and flattened, removing needless nesting.
Compatibility
Latest build for each game version and loader.
Only full game releases are shown. This mod publishes no snapshot builds.
Use cases
Large modpacks
Packs that add many complex blocks gain the most from the compact storage and geometry changes.
Client memory limits
Players with limited memory on the client can reduce usage when multi-part block models are present.
Who it’s for: Players and pack makers who run many mods on Fabric 1.16.5 – 1.17.1 and want lower memory use. The project is archived, so it suits setups that will not need further updates.
How it compares
FerriteCore is an alternative that is open source under the MIT License, with Fabric, Forge, NeoForge and Quilt files for 1.16.5 – 26.3, and the author recommends it for larger memory gains in modded play. Memory Leak Fix is open source under the GNU Lesser General Public License v2.1 only, with Fabric, Forge and Quilt files for 1.14.4 – 1.20.4 and the same client or server environment. Video Tape is client-side only, licensed under MIT-0 and not open source, with Fabric files for 1.18 – 1.20.6.
| Mod | Loaders | Game versions | Environment | Updated |
|---|---|---|---|---|
| Hydrogen | Fabric | 1.16.5 – 1.17.1 | Client or server, optional | 2021-07-15 |
| FerriteCore | Fabric, Forge, NeoForge and Quilt | 1.16.5 – 26.3 | Client or server, optional | 2026-03-24 |
| Memory Leak Fix | Fabric, Forge and Quilt | 1.14.4 – 1.20.4 | Client or server, optional | 2024-01-06 |
| Video Tape | Fabric | 1.18 – 1.20.6 | Client-side only | 2025-12-01 |
Questions
Does Hydrogen need Fabric API?
Does Hydrogen have to be installed on the server?
Is Hydrogen still updated?
Which game versions does Hydrogen support?
In the catalog
Hydrogen is one of 3,545 Optimization mods on ModsFinder, and one of 2,575 Optimization mods for Fabric. 4,181 mods support Minecraft 1.17.1.
More from CaffeineMC
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What the author says
This repository has been archived as we do not have the time or resources needed to maintain the project. No further updates will be published, and we won't be providing help for using it. If you are looking for a replacement, consider taking a look at FerriteCore, as it generally offers more significant improvements…
Official listing
- Modrinth page
- modrinth.com/mod/hydrogen
- Owner
- CaffeineMC
- Published
- 2021-01-17
- Updated on Modrinth
- 2021-07-15
- Facts verified
- 2026-10-15