---
title: Prerequisites
---

Hot-Join requires the following mods:
- Fabric API
- Concentration

There are 2 ways of using Hot-Join, either with **Auth Me** or with **Legacy4J**.

To see the relevant pages both, see [Usage with Auth Me](authme) and [Usage with Legacy4J](legacy4j)

<Callout>
After launching the second instance, it may take awhile for the 2nd client to load.
</Callout>