ParrelSync: Testing Unity Multiplayer in the Editor Without Building

What ParrelSync solves for Unity multiplayer testing

Testing networked gameplay in Unity normally means building the project, launching the build, and repeating that cycle for every change. ParrelSync removes the build step. It is a Unity editor extension that, per the README, "allows users to test multiplayer gameplay without building the project by having another Unity editor window opened and mirror the changes from the original project." The audience is narrow and specific: Unity developers working on multiplayer who want a second editor instance acting as a client or server on the same machine. The README frames the payoff as testing project changes on clients and server within seconds, both in the editor. If you are not doing networked work, or you already have a build pipeline fast enough that the build step is not the bottleneck, this tool has nothing to offer you.

How the clone mechanism works: symbolic links, not copies

The README describes the mechanism directly. For each clone instance, ParrelSync makes a copy of the original project folder and references the Asset, Packages and ProjectSettings folders back to the original project with symbolic links. Other folders such as Library, Temp, and obj remain independent for each clone. That split is the whole design. Shared folders mean a script edit in the original shows up in the clone without a copy step; independent Library, Temp and obj folders mean the two editors do not fight over the same import cache or compiled artifacts, which is what would break if you simply duplicated the project folder. Clones are placed right next to the original project with a _clone_x suffix, so the folder hierarchy looks like this:

Installing ParrelSync and opening your first clone

The README lists two install paths. The first is a .unitypackage from the latest release, imported into the project. Before either path, the README tells you to back up your project folder or use a version control system such as Git or SVN. That instruction is not boilerplate: the tool creates sibling folders and symbolic links, so an unexpected state is possible and a clean restore matters.

The second path is UPM. After Unity 2019.3.4f1 and Unity 2020.1a21, which support the path query parameter of git packages, you can add the package through the Package Manager with this URL:

https://github.com/VeriorPies/ParrelSync.git?path=/ParrelSync

Alternatively, add the same source to Packages/manifest.json:

"com.veriorpies.parrelsync": "https://github.com/VeriorPies/ParrelSync.git?path=/ParrelSync"

After import, the README says ParrelSync should appear in the menu item bar. From there the GUI tools manage the clones. The README does not walk through the exact menu clicks for creating the first clone; it points to the wiki's Installation-and-Update page for more detail. Once a clone exists, the API example shows the intended split in code:

if (ClonesManager.IsClone()) {
  // Automatically connect to local host if this is the clone editor
}else{
  // Automatically start server if this is the original editor
}

The README documents ClonesManager.IsClone() and points to a wiki page titled List of APIs for the rest. The Examples folder in the repository contains CustomArgumentExample.cs, which is the only example file listed at the top level.

Where ParrelSync stops being the right tool

The README states that ParrelSync currently supports Windows, macOS and Linux editors, and lists Unity 2022.3.56f1 LTS, 2021.3.29f1 LTS and 2020.3.1f1 LTS as tested versions, adding that it should also work with other versions. That is a claim about the tested set, not a guarantee. The more structural limitation is the symbolic link dependency. The README itself links to the Windows mklink documentation to explain the technique, which tells you the tool is leaning on an OS feature that behaves differently across platforms and filesystems. A project stored on a filesystem or sync service that does not preserve symbolic links will not behave the way the README describes. There is also a scope limit: the clone is a second editor on the same machine, so anything that depends on a real build, a separate device, or platform-specific networking behaviour is outside what this tool tests. The README does not document rollback or how to remove a clone cleanly, and it does not describe what happens if you delete the original project folder while clones exist. Those gaps are worth knowing before you rely on it.

ParrelSync compared with building and running a standalone player

The obvious alternative is the standard Unity workflow: build a standalone player and run it alongside the editor. The difference in approach is what gets shared. A build produces a self-contained player with its own compiled assemblies and its own copy of the assets; ParrelSync instead keeps a second editor alive and symlinks Asset, Packages and ProjectSettings back to the original. That means a script change appears in the clone without a rebuild, which is the entire reason the tool exists. The cost is that you are testing inside the editor, so editor-only behaviour and editor performance characteristics are part of what you observe. If your bug only reproduces in a build, or you need to test on a second physical machine or a console, ParrelSync does not replace the build. The README also credits hwaet's UnityProjectCloner as the origin of the project, which is another point of comparison if you want to look at the earlier approach.

Maintenance, licence and upgrade cost

The repository is not archived, and the last push was on 2026-06-16. The most recent release listed is 1.5.3 from 2024-06-16, preceded by 1.5.2 in 2023 and 1.5.1 in 2021. The gap between the 1.5.3 release and the most recent push suggests the project is not dormant, but the release cadence is slow, so you should not expect frequent version bumps. Upgrades are package imports or a manifest.json edit, which is cheap; the real cost is re-verifying that clones still open correctly after a Unity upgrade, since the tested version list in the README stops at 2022.3.56f1 LTS. The project is MIT licensed. That is a permissive licence, but the README does not discuss attribution requirements or what the licence means for redistribution, so read LICENSE.md yourself rather than treating a summary as legal advice.

Editorial conclusion

Adopt ParrelSync if you are iterating on networked gameplay in a single-machine Unity project and you want a second editor instance running a client within seconds instead of a full build. Do not adopt it if your project already shares assets through a version control workflow that cannot tolerate symlinks, or if you need a shipped build to validate platform-specific networking. Before you commit, verify that your Unity version is one the README lists as tested, that your project is under version control or backed up, and that your clone folders land where you expect them. The whole tool rests on symbolic links, so the first thing to check on your machine is whether the clone opens and sees the same assets as the original.

Frequently asked questions

Official sources

1. Issues
2. License: MIT
3. README
4. Releases
5. VeriorPies/ParrelSync on GitHub