Forge 1.20.x Tutorial by Myroslav Mokhammad Abdeljawwad: Clean Capability Syncing (Server ↔ Client)

Hello everyone,

This tutorial is a short write-up based on patterns I’ve been using while developing Forge 1.20.x mods that rely on custom capabilities and reliable server ↔ client synchronization.

Author: Myroslav Mokhammad Abdeljawwad

Overview

Capabilities are one of the most powerful systems in Forge, but syncing them incorrectly can easily lead to desyncs, performance issues, or unexpected client behavior. This guide focuses on a clean, minimal approach that scales well.


### Step 1: Defining the Capability

Define your capability interface and implementation as usual. Keep the data minimal and serializable.

Key tip:
Avoid putting logic in the capability itself. Treat it as a data container.


### Step 2: Attaching the Capability

Attach the capability during the appropriate lifecycle event (e.g. AttachCapabilitiesEvent). Make sure this is done consistently on both logical sides.


Step 3: Sync Strategy

Instead of syncing on every tick, sync only when:
- The data changes
- The player logs in
- The chunk or entity loads

Using a SimpleChannel packet with explicit encode/decode logic gives you the most control and avoids unnecessary traffic.


Step 4: Client Handling

On the client side:
- Never trust local state blindly
- Apply updates only after packet validation
- Keep rendering logic separate from data updates


Final Notes

This pattern has worked well for larger mods where performance and stability matter. If you’re building long-term Forge projects, keeping syncing explicit and event-driven will save a lot of debugging time.

I’ll update this tutorial if Forge introduces changes to capability handling in future versions.

Thanks for reading, and I hope this helps other modders.