NetBird is an open-source, WireGuard-based overlay networking and Zero Trust Network Access platform for connecting remote users, cloud and on-premises resources, edge devices, containers, and agents through peer-to-peer encrypted tunnels. Its agents manage WireGuard connections, obtain peer candidates through ICE and STUN, exchange connection information through a signaling service, and use a relay when direct connections fail. A centralized management service maintains network state, peer addresses, access policies, and configuration updates, while the admin interface supports identity-based access control, network segmentation, SSO, MFA, device posture checks, private DNS, routes, exit nodes, SSH, reverse proxying, activity logging, and integrations such as Terraform and Ansible. NetBird can run as a hosted cloud service or be self-hosted; its repository includes the client, management, signal, and relay components, with most code licensed under BSD-3-Clause and the management, signal, and relay directories under AGPLv3.