CurseForge · Minecraft mod
ModernFix
All-in-one mod that improves performance, reduces memory usage, and fixes many bugs. Compatible with all your favorite performance mods!
Quick answer
Which ModernFix release matches 1.21.1 NeoForge?
modernfix-neoforge-5.27.20+mc1.21.1.jar targets 1.21.1 with NeoForge. The project page does not say whether it belongs on the client. The project page does not say whether it belongs on the dedicated server. No extra mods listed for this file.
Where it goes
Is ModernFix required on the client, server, or both?
The project page does not say whether it belongs on the client. The project page does not say whether it belongs on the dedicated server.
The source does not explicitly classify this release as client-only or server-only.
What else does modernfix-neoforge-5.27.20+mc1.21.1.jar need?
modernfix-neoforge-5.27.20+mc1.21.1.jar on 1.21.1 NeoForge. Every mod below is checked against that same setup.
This file does not list any required mods. Do not add a library just because a different file uses it.
This file does not list any required or optional mods.
Before you install it
Add ModernFix without breaking your instance.
Built for modernfix-neoforge-5.27.20+mc1.21.1.jar on 1.21.1 NeoForge. Pick another file and the loader, install side or required mods may change.
- 01
Stick to this file
Use modernfix-neoforge-5.27.20+mc1.21.1.jar. It targets 1.21.1 with NeoForge; another release may have different loader, side or dependency requirements.
- 02
Bring the mods it needs
This file does not list any required mods. Do not add a library just because a different file uses it.
- 03
Put it on the correct side
The project page does not say whether it belongs on the client. The project page does not say whether it belongs on the dedicated server.
- 04
Pick the file you checked
Use the “Get this file” button beside modernfix-neoforge-5.27.20+mc1.21.1.jar. It opens that exact file at the source.
About this project
What does ModernFix add?

ModernFix is an all-in-one mod that improves performance, reduces memory usage, and fixes many bugs in modern Minecraft versions (most versions including and above 1.16 are supported) without majorly compromising the game experience. Most Forge 1.16-1.19.2 modpacks will launch roughly twice as fast with ModernFix installed. If some non-default options are enabled, it can even allow large modpacks like All The Mods 8 to run with 3GB or less of allocated memory.
ModernFix is free, open-source software. All of the code is available on the GitHub repository.
⚙️ Technical summary
What exactly does ModernFix do for your game? There are a lot of tweaks being made - too many to summarize here. However, here is a brief summary of the general types of improvements being made:
- Backports of bugfixes from newer versions of Minecraft and/or Forge, e.g. fixing worlds breaking when you remove a dimension mod in 1.18.
- Patches to mods that are no longer supported on a given Minecraft version, to improve the gameplay experience instead of requiring players to update.
- Many optimizations & improvements to the game's launch process to significantly improve speed and reduce random concurrency crashes.
- Additional debug tools to help modders and players determine the cause of some rare game crashes/freezes, instead of relying on a painful mod bisection process.
- It's not enabled by default due to compatibility issues, but ModernFix includes functionality to completely redesign the game's model loading system, replacing it with a new, dynamic version that loads models on the fly. Model loading is one of the major performance regressions to modded Minecraft that has been present since 1.8, and this new system alleviates nearly all of the downsides, bringing memory usage and loading times more in line with how they were in 1.7.10.
- Need to play the vanilla game with very little RAM allocated (e.g. 512MB or less)? Now you can do that. Head to the "Ultra-Low Memory Footprint" page on the wiki.
If you are technically savvy and looking for more details on each patch, I recommend reading the Summary of Patches wiki page.
🐛 Where to go when something doesn't work
Please either report an issue on GitHub, or join the Discord and ask in the #modernfix-discussion channel. Be sure to mention the Minecraft version, modloader, and ModernFix version you are using, as well as what other mods you have installed.
🎁 How can I support this project?
There are two main ways you can help support the development of ModernFix:
- Spread the word! Test ModernFix in modpacks and encourage them to include it.
- If you feel generous, I do accept donations via Ko-fi. Donating is not required (as ModernFix is free), but every little bit helps. I work on ModernFix in my spare time, so any compensation I receive helps to sustain development.
❓ What other mods should I use?
There are many performance mods available for Minecraft and I can't list them all here, but here are some essential mods, in my opinion:
- On any version before 1.19.4 you should always have LazyDFU installed, as it eliminates the incredible lag caused by the DFU system.
- On any version before 1.20 you should generally use Starlight unless it has a compatibility issue with your mods (which is quite rare). It offers vastly improved lighting performance and can also fix FPS stutters when moving between chunks.
- Always have FerriteCore installed, as Mojang's implementation of blockstates/models is laughably inefficient, and quickly consumes RAM as soon as more content is added beyond what vanilla offers.
- Install a mod like Shutup Experimental settings (before 1.19) or Yeetus Experimentus (1.19+). These mods will suppress the pop-up screen about experimental game features, which otherwise causes the game to reload its resources twice.
On a related note: I do not recommend use of OptiFine in any modded scenario. It is closed-source, patches the game in a way that easily breaks Forge and other mods, and significantly slows down game launching, often on the order of minutes. Please consider using Sodium (on Fabric) or Embeddium (on Forge) instead. Using OptiFine with ModernFix is not officially supported, and may cause issues.
Need a Minecraft server? Consider CreeperHost!

Project description from CurseForge.
Pick your setup
ModernFix by Minecraft version and loader
Choose the version and loader you play, then open the matching release.
1.21.1
1 loader build1.20.1
1 loader buildCheck the dependencies, then try the file in a copied instance before changing a world you care about.
Recent files
ModernFix versions and loaders
modernfix-neoforge-5.27.20+mc1.21.1.jar
18 Jul 2026
modernfix-neoforge-5.27.15+mc1.21.1.jar
2 Jul 2026
modernfix-neoforge-5.27.14+mc1.21.1.jar
16 Jun 2026
modernfix-neoforge-5.27.12+mc1.21.1.jar
9 Jun 2026
modernfix-neoforge-5.27.11+mc1.21.1.jar
25 May 2026
modernfix-neoforge-5.27.10+mc1.21.1.jar
25 May 2026
modernfix-neoforge-5.27.9+mc1.21.1.jar
23 May 2026
modernfix-neoforge-5.27.8+mc1.21.1.jar
16 May 2026
modernfix-neoforge-5.27.7+mc1.21.1.jar
8 May 2026
modernfix-neoforge-5.27.6+mc1.21.1.jar
6 May 2026
modernfix-neoforge-5.27.5+mc1.21.1.jar
6 May 2026
modernfix-neoforge-5.27.4+mc1.21.1.jar
28 Apr 2026
Looking for an older file? The official CurseForge project page is in Resources.