# EOS Multiclient Dev Kit - launch multiple real EOS clients from one machine (UE 5.7, free)

**URL:** <https://forums.unrealengine.com/t/eos-multiclient-dev-kit-launch-multiple-real-eos-clients-from-one-machine-ue-5-7-free/2741242>\
**Category:** Plugins\
**Tags:** unreal-engine, EOS, editor, Plugins, multiple-instance, CPP\
**Created:** [August 4, 2026, 8:23pm UTC](https://forums.unrealengine.com/t/eos-multiclient-dev-kit-launch-multiple-real-eos-clients-from-one-machine-ue-5-7-free/2741242 "2026-08-04T20:23:59Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![Official\_rimacc](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@Official\_rimacc](https://forums.unrealengine.com/u/Official_rimacc)\
**Post date:** [August 4, 2026, 8:23pm UTC](https://forums.unrealengine.com/t/eos-multiclient-dev-kit-launch-multiple-real-eos-clients-from-one-machine-ue-5-7-free/2741242/1 "2026-08-04T20:23:59Z")

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Testing EOS multiplayer locally is more tedious than it should be. You need a separate Epic account per test player, the DevAuthTool running with a credential for each, and then every single test means launching several standalone clients by hand with the right command line arguments. Before any of that there is the EOS config itself, where a wrong section name or a missing line fails silently and costs you an afternoon.

I built a plugin to remove most of that. Free, source available, and editor only, so nothing from it ships in your packaged build.

 ![QuickLaunch](https://d3kjluh73b9h9o.cloudfront.net/original/4X/6/b/8/6b8213ae2344f172cd350443692528864ca82334.jpeg)_[screenshot: Quick Launch tab]_

**Quick Launch** starts 2 to 4 standalone clients, tiled, each its own process with its own EOS login and its own log file. It passes the stock `AUTH_TYPE` / `AUTH_LOGIN` / `AUTH_PASSWORD` switches, so any project that calls `IOnlineIdentity::AutoLogin` picks up the right account with no extra code.

**Setup** writes your credentials to DefaultEngine.ini and fills in every other line EOS needs: `DefaultArtifactName`, `bUseEAS`, `bUseEOSConnect`, the overlay flags, `DefaultPlatformService`, and the net driver definitions. It only adds lines that are missing and never overwrites values you set yourself.

**Validate** runs 12 checks for the usual pitfalls. `AuthScopeFlags` crashing EOSShared on startup, a bare `[EOSSettings]` section instead of the full path, `DefaultArtifactName` not matching your Artifacts entry, NetDriverEOS configured but never winning because the ClearArray line is missing, and so on.

 ![Validate](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/3/5/235c55e071709693df48151273e022292a682ab9.jpeg)

_[screenshot: Validate tab]_

**Package** handles the post-package step for the EOS overlay in shipped builds, generating Play.exe through Epic’s bootstrapper tool.

Requirements, so nobody is caught out:

- UE 5.7, Windows
- Your game needs to call `IOnlineIdentity::AutoLogin` somewhere, which is the standard EOS pattern
- The DevAuthTool still has to be running with credentials named to match. That is Epic’s tool and I cannot redistribute it, so there is a Dependencies folder you drop it into
- You still need a separate Epic account per test player. Nothing gets around that

> **[GitHub - official-rimacc/EOSMulticlientDevKit: In-editor multiplayer testing for Epic Online...](https://github.com/official-rimacc/EOSMulticlientDevKit)**
>
> In-editor multiplayer testing for Epic Online Services - multiple real EOS clients from one machine, plus config validation and one-click setup. UE 5.7 editor plugin.

License is source available. Free for commercial use, including shipped games, studio work, client work and paid services, and anything you build using it is entirely yours. The only restrictions are on the kit itself: you cannot resell it or pass it off as your own.

Happy to answer questions here. If you hit an EOS problem the validator should have caught, tell me and I will add a check for it.