Uranium (Lag)
by Yosa
Uranium (Lag) is a client-side Optimization mod that deliberately wastes processing power to make the game stutter and run at very low frame rates.
What it does
Instead of describing bad performance as a side effect, the mod recreates it on purpose: it spends processing time so that the game becomes stuttery and drops to extremely low FPS. The author describes it as a tool for testing patience and resilience, since the game can become close to unplayable with it installed.
Uranium (Lag) adds some new gameplay content in the form of blocks and items, and it can change visuals as well. Its code is open to inspection, so anyone can confirm what the mod does before installing it. It is available for both Fabric and Forge, with files for game versions 1.20 – 1.20.6 and the latest builds published on 2026-01-04. Because it is client-side only, players install it themselves and servers do not need it.
Key features
Deliberate lag
The mod spends processing power on purpose, producing stuttering and extremely low FPS in the game.
Blocks and items
New blocks and items are added to the game alongside the lag effects, for use in challenge scenarios.
Visual changes
The mod can modify how the game looks, adding to the difficulty of playing with it installed.
Public source code
The source is published for anyone to read, so its behavior can be checked against the description.
Gallery
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: The mod suits players who want a joke, a stress test or a challenge scenario, and modpack makers who build intentionally broken setups. It is not meant for everyday play on a working system.
How it compares
WhatsMyLag is a Fabric and Quilt mod that works on either side, and neither side needs it, published under All rights reserved; it measures lag rather than causing it. Uranium fuel is a Forge mod for 1.20.1 that runs on client and server and is also under All rights reserved, so it serves a different purpose than the lag effects here.
| Mod | Loaders | Game versions | Environment | Updated |
|---|---|---|---|---|
| Uranium (Lag) | Fabric and Forge | 1.20 – 1.20.6 | Client-side only | 2026-01-04 |
| WhatsMyLag | Fabric and Quilt | 1.20 – 1.20.6 | Client or server, optional | 2025-10-06 |
| Uranium fuel | Forge | 1.20.1 | Client and server | 2024-08-20 |
Questions
Does Uranium (Lag) need to be installed on the server?
Is the source code available?
In the catalog
Uranium (Lag) is one of 3,545 Optimization mods on ModsFinder, and one of 2,575 Optimization mods for Fabric. 11,154 mods support Minecraft 1.20.6.
More from Yosa
Similar mods
What the author says
Introducing Uranium, a mod designed to take your Minecraft experience to a new level of challenge by introducing intentional lag. This mod makes the game unplayable, testing your patience and resilience. Uranium was originally created as a joke to show friends how Minecraft used to run on my PC. Instead of describing…
Official listing
- Modrinth page
- modrinth.com/mod/uranium-lag
- Owner
- Yosa
- Published
- 2026-01-04
- Updated on Modrinth
- 2026-01-04
- Facts verified
- 2026-10-15