Block Outline FX

Block Outline FX is a client-side Fabric mod for Minecraft 1.21.4 that upgrades the vanilla block outline with fully configurable visuals.

556 Downloads

fabric

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About this Mod

Block Outline FX is a client-side Fabric mod for Minecraft 1.21.4 that upgrades the vanilla block outline with fully configurable visuals.

Main Features

Custom outline color (RGB + alpha)
Through-walls outline mode
Visual effects: rainbow, pulse, sparkle
In-game vanilla-style settings screen
Mod Menu config integration
Hotkeys for quick access (O) and enable/disable (K)

Compatibility

Minecraft: 1.21.4
Loader: Fabric
Environment: Client-side only

Author

aizero_o

Available Versions

Block Outline FX 1.0.0release

MC 1.21.4fabric

March 9, 2026

How to Install Block Outline FX 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 (1.21.4).

Install Mod

Open the mod browser in the dashboard and search for "Block Outline FX". Click "Install" – done! Alternatively, upload the .jar via SFTP to the /mods folder.

Compatibility

Mod Loaders

fabric

Minecraft Versions

1.21.4

Server-side

✗ Unsupported

Recommended RAM

4 GB(min. 3 GB)

Frequently Asked Questions

Block Outline FX 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 (1.21.4). You can switch loaders with one click in the panel.

Is Block Outline FX compatible with fabric?

Block Outline FX officially supports fabric for Minecraft 1.21.4. The Mado dashboard automatically detects incompatible loader combinations.

Server lagging with Block Outline FX – how to optimize performance?

Recommended RAM: 4 GB (per 8 players). Use /spark profiler to check if Block Outline FX 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.