Nebula
An open-source overlay network from Slack, using certificates to connect hosts at scale.
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About Nebula
Nebula is an overlay networking tool originally built at Slack to connect tens of thousands of servers across data centres and clouds. Each host gets a certificate signed by your own certificate authority, which defines its identity and security groups, and lighthouse nodes help peers find each other so they can connect directly through NAT. Firewall rules are written against those groups, so access control is part of the network itself. It is fast, mature and fully self-hosted, but you manage the certificate authority, configuration files and lighthouses yourself, which is more work than consumer mesh tools. Defined Networking, founded by Nebula's creators, sells Managed Nebula with automated certificates, SSO and a web UI, free for small networks and billed per host above that. Nebula runs on Linux, macOS, Windows, iOS, Android and FreeBSD. It suits infrastructure teams and technical users who want a self-run mesh without depending on a vendor.
Best for: Infrastructure teams that want a self-run mesh with certificate-based access control.
Pros and cons
What works
- Proven at very large scale
- Access control built into host certificates
- Fully self-hosted with an optional managed service
Why people leave
- Manual certificate and config management
- Steeper learning curve than Tailscale
- Mobile apps are less polished
Top Nebula alternatives
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Why people left Nebula
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Nebula: common questions
Is Nebula free?
Yes. Nebula is free, open-source software that you can host yourself.
Is Nebula open source?
Yes. The source code is on GitHub at slackhq/nebula. You can also run it on your own server.
What platforms does Nebula run on?
Nebula is available for Linux, macOS, Windows, iOS, Android and Self-hosted.
What are the best alternatives to Nebula?
The highest-ranked Nebula alternatives right now are Tailscale, NetBird and ZeroTier. See the full ranked list for pricing, platforms and verified facts.