Open5GS is an open source implementation, written in C, of the core network used by 4G and 5G mobile systems. The project is led by its main author, Sukchan Lee, together with contributors on GitHub. According to the release log on the official site, coding began in February 2017, and the Open5GS name arrived with version 1.0.0 in October 2019. The code is released under the GNU AGPL v3.
Version 2.8.0, published on 20 June 2026, brings the protocol definitions in line with Release 19 of the 3GPP, the body that writes mobile network standards. The GitHub release notes also list several security fixes in the AMF and in GTP-U and PFCP message handling.
What Open5GS is for
A mobile network has two layers. The radio access side, with base stations known as eNodeBs in 4G and gNodeBs in 5G, talks to the phones. The core decides who may attach, hands out IP addresses, enforces quality of service rules and carries traffic out of the network. Open5GS deals only with that second layer. It splits the core into small daemons, one per standardised network function, which can all run on a single machine for testing or be spread across several servers.
For 4G the project provides the MME for mobility, the HSS for authentication keys, the PCRF for policy and charging and the SGW and PGW gateways, each split into control and user planes. For 5G standalone, known as SA, it follows the 3GPP service-based architecture: the AMF handles registration and mobility, the SMF manages sessions, the UPF forwards packets, backed by around ten other functions such as the NRF, UDM and PCF. Subscriber records live in a MongoDB database, and an optional web interface built on Node.js lets you add SIM profiles without touching the command line.
The official tutorials are a good indication of what people do with it: attaching a base station, bringing a commercial smartphone onto a 5G SA network with a programmable SIM card, setting up voice over LTE with the Kamailio IMS, testing roaming between two networks or exporting metrics to Prometheus. For the radio side, those guides use software from Software Radio Systems, the company behind srsRAN.
Its position among open source telecom tools is fairly clear. Osmocom, the other major open source mobile suite, focuses on 2G and 3G, whereas Open5GS targets 4G and 5G. Most deployments are private networks: university labs, test benches where manufacturers validate devices, coverage for remote sites, or integrator demos. Sponsors listed on the site include sysmocom, P1 Security and Kontron.
Who is it for?
Open5GS is aimed at telecom engineers, researchers, lecturers who want to show how a 5G core works from the inside, and companies building their own private network. A Linux administrator with networking experience can install the Ubuntu packages with a handful of commands, and the default configuration runs every function on one host using loopback addresses, so a first test needs no special infrastructure.
The limits deserve a frank look. Open5GS has no radio component, so without a base station and devices carrying SIM cards whose keys you know, there is no actual network. Running it well means understanding the S1, NG and N4 interfaces, IP routing and the YAML configuration of each function. In most countries, transmitting on cellular frequencies also requires permission from the regulator. Legacy 2G and 3G networks are out of scope, and Osmocom is the place to look for those. If the goal is simply to dissect signalling messages without building a network, Pycrate or Scapy, already in our software library, will be a better fit.
Download Open5GS safely
The official sources are open5gs.org and the github.com/open5gs/open5gs repository, where each release is published as a source archive. The quickstart guide points to an Ubuntu PPA called open5gs/latest, Debian packages built on the Open Build Service and a repository for openSUSE, plus build instructions for Fedora, CentOS, Alpine, FreeBSD and macOS on both Intel and Apple Silicon. Community projects add Docker setups and Helm charts.
The software is free of charge and has no paid tier. Its author is funded through GitHub Sponsors, Open Collective and Buy Me a Coffee. The contributor licence agreement does, however, allow the code to be offered under other licences and inside proprietary products. Because a mobile core stores every subscriber’s secret keys, it is wise to avoid prebuilt virtual machines of unknown origin and to stick with the PPA, the OBS packages or the code in the official repository.
Frequently asked questions
Is Open5GS free?
Yes. It is distributed under the GNU AGPL v3 with no paid version. The licence requires you to publish your changes if you run a modified version to serve users, including over a network.
Does Open5GS support 5G standalone?
Yes. It includes both the 4G core, known as the EPC, and a 5G SA core with the AMF, SMF, UPF and the other service-based functions. The 4G core can also anchor a non-standalone 5G deployment.
Do I need radio hardware?
For a real network, yes: you need a 4G or 5G base station and SIM cards programmed with known keys. Without hardware, you can still study the core by connecting it to a software simulator of a base station and handset.
