ModsFinder

CustomLag

by scrythe

CustomLag lets a server owner simulate network lag on a Fabric server, with delayed packets and adjustable latency.

FabricServer-side onlyMIT LicenseOpen source1.21 – 1.21.11

What it does

Set through commands, CustomLag delays packets the server sends and receives, so latency can be tested against a running world, including single-player worlds opened to LAN. Values are written to a TOML file and kept after a restart, and settings can be applied to players who have not joined yet. Only the server needs the mod, so players join without installing anything. The mod requires Fabric API and is released under the MIT License as open source, for 1.21 – 1.21.11 with 1.1.0 as the latest file for 1.21.11.

Key features

  1. Simulated latency

    Packet sending and receiving can be delayed to imitate a slow connection on the server.

  2. Per-player lag command

    A command changes the latency or ping for a chosen player, and a second command removes it.

  3. Saved settings

    Lag values are stored in a TOML file, so they remain in place after the server restarts.

Compatibility

Latest build for each game version and loader.

1.21.x12 of 12 versions with builds
1.21.111.1.0+1.21.11
1.21.101.1.0+1.21.9-1.21.10
1.21.91.1.0+1.21.9-1.21.10
1.21.81.1.1+1.21.6-1.21.8
1.21.71.1.1+1.21.6-1.21.8
1.21.61.1.1+1.21.6-1.21.8
1.21.51.1.1+1.21.5
1.21.41.1.0+1.21-1.21.4
1.21.31.1.0+1.21-1.21.4
1.21.21.1.0+1.21-1.21.4
1.21.11.1.0+1.21-1.21.4
1.211.1.0+1.21-1.21.4
ReleaseBetaAlphaNot available

Only full game releases are shown. This mod publishes no snapshot builds.

Requirements

Dependencies declared by the latest file for each loader.

Required 1

Fabric APILightweight and modular API providing common hooks and intercompatibility measures utilized by mods using the Fabric toolchain.
Required

How it compares

Full comparison

Lag Protect is the server-side Fabric option that also has MIT License and open source status, with files for 1.20.5 – 26.2. Chat Disabler is a client-side Fabric mod under the MIT License, not open source, for 1.21 – 1.21.11.

ModLoadersGame versionsEnvironmentUpdated
CustomLagFabric1.21 – 1.21.11Server-side only2025-12-29
Lag ProtectFabric1.20.5 – 26.2Server-side only2026-08-20
Chat DisablerFabric1.21 – 1.21.11Client-side only2026-05-01

Questions

Does CustomLag need Fabric API?

Yes. Fabric API is a required dependency and must be installed alongside CustomLag.

In the catalog

CustomLag is one of 8,016 Management mods on ModsFinder, and one of 5,930 Management mods for Fabric. 19,862 mods support Minecraft 1.21.11.

Management mods8,016Fabric modsMods for 1.21.1119,862

Similar mods

Cherished Worlds1.12.2 – 26.3Default Options1.18 – 26.3Axiom1.20 – 26.3Resourcify1.8.9 – 26.3Rebind Narrator1.16.1 – 26.1.2Paxi1.19.2 – 26.1.2

What the author says

Your browser doesn't support HTML video. 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.)
scrythe, on the Modrinth page

Official listing

Owner
scrythe
Published
2025-08-14
Updated on Modrinth
2025-12-29
Facts verified
2026-10-15

Tags

Game mechanicsManagementUtility
Open on ModrinthCompare