free5GC: A Go-Based 5G Core for Labs and Prototypes, Not Production

Why a 5G Core Needs an Open Source Option

5G core networks are typically locked inside vendor equipment, making them expensive and hard to modify. free5GC addresses this by providing a full implementation of the 5G core, defined in 3GPP Release 15 and later, as open source. The project is under the Linux Foundation umbrella, which gives it a governance structure beyond a single company. Its primary audience is researchers, students, and network engineers who need a working core for testing, development, or proof-of-concept setups. Without an open source core, these groups would have to rely on proprietary simulators or costly lab equipment, which slows down innovation and learning. free5GC aims to fill that gap by offering a codebase that can be inspected, modified, and run on commodity hardware.

Architecture: A Modular Set of Go Services

The repository layout shows that free5GC is not a monolithic application. It is composed of multiple network functions, each implemented as a separate service, which mirrors the service-based architecture of 3GPP 5G cores. The code is written in Go, a language chosen for its concurrency support and ease of deployment as static binaries. The README does not list the individual network functions, but the project's documentation on free5gc.org/guide/ describes the typical components: AMF, SMF, UPF, NRF, UDM, and others. Each function runs independently and communicates via HTTP/2-based interfaces, as defined by 3GPP. This modularity means you can deploy only the functions you need, or run them all on a single machine for a minimal test environment. The trade-off is that managing multiple services adds operational complexity compared to a single-process core.

Getting Started: What the Repository Actually Tells You

The README is sparse on setup instructions. It points to the official guide at free5gc.org/guide/ for documentation, and to the forum for questions. It does not include a quickstart command or a Docker Compose file. To get it running, you would need to clone the repository, ensure you have a Go toolchain, and then follow the guide's steps, which typically involve configuring each network function's YAML files and starting them in a specific order. The release notes for v4.2.3, v4.2.2, and v4.2.1 are referenced but not detailed in the README. Based on the repository structure, you can expect to build binaries with `go build` in each function's directory, or use the provided scripts if they exist. Without hands-on testing, the exact command sequence remains unclear, so plan to consult the guide and forum for your specific environment.

Licensing and Governance: Apache-2.0 and Linux Foundation

free5GC is licensed under Apache-2.0, which is permissive and allows commercial use, modification, and redistribution, provided you retain the license notice. This is a significant advantage over some open source telecom projects that use copyleft licenses, which can complicate proprietary integrations. The project is also a Linux Foundation project, which suggests a neutral governance model and a commitment to long-term maintenance. However, the README does not provide details on contribution guidelines beyond a link to pull requests, nor does it mention a code of conduct or a steering committee. The release cadence is visible: v4.2.3 came out on 2026-06-30, v4.2.2 on 2026-04-21, and v4.2.1 on 2026-03-04, indicating roughly monthly releases. That pace is healthy for a project of this complexity, but it also means you should expect frequent changes and potential breaking updates.

The Hard Limits: Not a Carrier-Grade Solution

The project's goal is to implement 3GPP Release 15 and beyond, but the README does not claim full compliance with any release. In practice, open source 5G cores often lag behind the standard, and free5GC is no exception. It is designed for testing and research, not for production traffic. Performance under load, fault tolerance, and security hardening are not addressed in the README. If you need to handle real subscriber traffic or meet regulatory requirements, this is the wrong tool. Another limitation is the lack of a built-in user interface or management plane; you must configure everything via files and commands, which requires deep knowledge of 5G signaling. The forum is the primary support channel, which means you rely on community answers rather than a vendor SLA. For a lab environment, these constraints are acceptable, but for a commercial deployment, they are deal-breakers.

Alternatives: What Else Is Out There

The main alternative to free5GC is Open5GS, another open source 5G core that is also written in C and Python. Open5GS has a longer history and a more mature user base, but it is not a Linux Foundation project and its license is AGPL-3.0, which is more restrictive for commercial use. The key difference is the language and the community: free5GC's Go codebase may be easier for developers familiar with Go, while Open5GS offers more documentation and a larger set of tutorials. Another alternative is a commercial core from vendors like Nokia or Ericsson, but those are closed source and expensive, which defeats the purpose of open source experimentation. For a quick lab test, you could also use a simulator like UERANSIM with free5GC, but that is a separate tool, not a core replacement. The choice between free5GC and Open5GS often comes down to licensing and language preference, not feature set, since both are incomplete compared to the 3GPP spec.

Maintenance and Upgrade Costs

The monthly release cycle means you need to track updates if you want bug fixes and new features. Upgrading a free5GC deployment involves rebuilding the affected network functions and re-testing the entire call flow, since changes in one function can impact others. The project does not provide a migration guide in the README, so you must rely on release notes and forum posts to understand what changed. The use of Go makes compilation straightforward, but it also means you need a current Go toolchain installed. The Apache-2.0 license reduces legal overhead for redistribution, but you are still responsible for any modifications you make. If you deploy free5GC in a lab, budget time for regular updates and regression testing. If you deploy it in a production-like environment, expect to invest significant effort in monitoring, logging, and failover, none of which are provided out of the box.

Editorial conclusion

Adopt free5GC if you need a free, modifiable 5G core for testbeds, research, or teaching, and you have the Go and networking skills to debug it. Skip it if you require carrier-grade reliability, full R17 compliance, or commercial support. Before committing, verify that your UE and RAN equipment interoperate with the current release, check the forum for known issues, and review the release notes to see if the features you need are present or still experimental.

Frequently asked questions

Official sources

1. Official documentation
2. Official README
3. Project repository
4. Release notes