
CustomLag
Fabric mod to simulate lag for servers and single player worlds by delaying packets from sending and receiving
Screenshots

About this Mod
About the Mod
This Mod simulates lag by delaying the processes of receiving and sending packets. This is done by injecting a ContextHandler inside the ChannelPipeline of a minecraft connection. This mod works only for servers and single player worlds.
Usage
To set or change the latency/ping for a player, just use the lag command:
/lag set <playername> <latency>
Setting lag will be saved to a toml file, so even after restart, the settings
will remain. You can also set the lag of offline players (who have not currently
joined yet.)
In order to remove the lag of a player, you can use:
/lag remove <playername>
(this removes the ContextHandler that delays packets from sending)
Some additional commands are:
There are also some addional quality of live -ish commands, like increase the
keep alive / ping packets interval, to find more, just enter
/customlag
Available Versions
How to Install CustomLag on Your Server
Order Server
Order a Minecraft Java server with at least 3 GB RAM (4 GB recommended).
Set fabric Loader
In the panel under "Egg", select the fabric loader and matching Minecraft version (1.21.11).
Install Mod
Open the mod browser in the dashboard and search for "CustomLag". Click "Install" – done! Alternatively, upload the .jar via SFTP to the /mods folder.
Compatibility
Mod Loaders
Minecraft Versions
1.21.11, 1.21.10, 1.21.9 (+9 more)
Server-side
✓ RequiredRecommended RAM
4 GB(min. 3 GB)Frequently Asked Questions
CustomLag server crashes on startup – what to do?
Most common cause: wrong fabric version or insufficient RAM. Check the server log (latest.log) for "OutOfMemoryError" or "Mixin" errors. With Mado Hosting: ensure at least 3 GB RAM is allocated and the loader matches the mod version (1.21.11). You can switch loaders with one click in the panel.
Is CustomLag compatible with fabric?
CustomLag officially supports fabric for Minecraft 1.21.11, 1.21.10, 1.21.9. The Mado dashboard automatically detects incompatible loader combinations.
Server lagging with CustomLag – how to optimize performance?
Recommended RAM: 4 GB (per 8 players). Use /spark profiler to check if CustomLag consumes the most tick time. Common fixes: reduce server view-distance to 8-10, install "performant" or "starlight" as supplementary mods on Forge. With Mado Hosting, your server runs on NVMe SSDs with dedicated CPU cores for minimal latency.
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Rent Modded Server
Install CustomLag with just one click on your server.