Tailscale Inc. is a software company based in Toronto, Ontario. Tailscale develops an open-source software-defined mesh virtual private network (VPN) and a web-based management service. The company provides a zero config VPN as a service under the same name.

The company's name was inspired by a 2013 Google research paper, The Tail at Scale.

In 2019, Google engineers Avery Pennarun, David Crawshaw, David Carney, and Brad Fitzpatrick founded Tailscale.

In November 2020, Tailscale secured funding of US$12 million in a Series A round, led by Accel, with seed investors Heavybit and Uncork Capital participating.

In May 2022, the company secured a US$100 million Series B round, led by CRV and Insight Partners, with participation from existing investors.

In April 2025, the company secured a US$160 million Series C round, led by Accel, with participation from CRV, Insight Partners, Heavybit, and Uncork Capital.

The open-source software acts in combination with the management service to establish peer-to-peer or relayed VPN communication with other clients using the WireGuard protocol.

Tailscale can open direct connection to the peer using NAT traversal techniques such as STUN or request port forwarding via UPnP IGD, NAT-PMP or PCP. If the software fails to establish direct communication, it falls back to using DERP (Designated Encrypted Relay for Packets) protocol relays provided by the company.