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Networking · head to head

Nebula vs OpenVPN

Nebula logo

Nebula

Networking

Certificate based overlay network from Slack, with identity and firewall rules carried in the certificate

From
Free
Rated
-
Full reviewWebsite
OpenVPN logo

OpenVPN

Networking

Open source VPN protocol with a commercial Access Server product priced per simultaneous connection

From
Free
Rated
-
Full reviewWebsite

The short version

  • Each has a real cost: Nebula the open source project has no user interface, no enrolment workflow and no revocation service, so certificate issuing, distribution and expiry become scripts you write and then have to keep working.; OpenVPN open source OpenVPN, while free, requires real technical skill to configure, secure and maintain without the Access Server admin layer
  • They diverge on capability: Nebula covers Certificate carried identity, OpenVPN covers Open source core.
  • Prices and features above were last checked on 1 September 2026.

Where they differ

Only the attributes on which Nebula and OpenVPN actually diverge.

Attributes where Nebula and OpenVPN differ
AttributeNebulaOpenVPN
Pricing modelOpen source, no licence feeOpen source core is free; Access Server billed per simultaneous connection
PlatformsLinux, macOS, Windows, iOS, Android, FreeBSDLinux, Windows, macOS, iOS, Android

Identical on both: starting price (Free), free tier (Yes), user rating (Not yet rated), category (Networking).

What each one covers

Drawn from each product's published feature list. An absence here means we hold no record of it - not that the product lacks it.

Only in Nebula

  • Certificate carried identity
  • Group based host firewall
  • Lighthouse discovery
  • Noise protocol encryption
  • Unsafe routes
  • Managed option

Only in OpenVPN

  • Open source core
  • Access Server admin UI
  • Per-connection licensing
  • Free tier
  • Cross-platform clients

What people use each for

The jobs each tool is most often brought in to do.

Nebula

  • Flattening a network across several clouds and datacentres without VPC peering or route tablesnot OpenVPN
  • Very large fleets where a central policy service on the connection path is unacceptablenot OpenVPN
  • Environments that already run an internal certificate authority and want the network to use itnot OpenVPN
  • Replacing per host iptables rules with policy written against roles that follow the hostnot OpenVPN

OpenVPN

  • A technical team wanting a fully free, self-configured VPN server using the open source protocol without any vendor relationshipnot Nebula
  • A small business wanting a supported, easier-to-administer VPN server, willing to pay per concurrent connection rather than per employeenot Nebula
  • An organisation with more staff than typical concurrent VPN usage, since Access Server bills only active simultaneous connections, not total accountsnot Nebula
  • An IoT or large-scale deployment needing custom Enterprise pricing above 2,000 connectionsnot Nebula

Where each one falls short

Documented limitations, not opinions. Every one is a constraint you would hit in normal use.

Nebula

  • The open source project has no user interface, no enrolment workflow and no revocation service, so certificate issuing, distribution and expiry become scripts you write and then have to keep working.
  • Revoking a compromised host means distributing a blocklist entry to every other host and reloading them, which is a fleet wide operation rather than a click, and easy to get wrong under pressure.
  • Changing a host group membership means reissuing and redeploying its certificate, so policy changes are a deployment rather than a configuration edit.
  • There is no identity provider integration or single sign on in the open source version, so it maps well to servers and badly to a fleet of user laptops.
  • NAT traversal is best effort and hosts behind symmetric NAT need a relay configured deliberately, so connectivity failures show up as intermittent rather than immediate and are awkward to diagnose.

OpenVPN

  • Open source OpenVPN, while free, requires real technical skill to configure, secure and maintain without the Access Server admin layer
  • Per-connection billing on Access Server means usage spikes, such as an all-hands remote day, can push simultaneous connections over a licensed limit and block new connections until usage drops or the plan is upgraded
  • OpenVPN's traditional hub-and-spoke architecture routes traffic through a central server, unlike mesh VPN tools like Tailscale or NetBird that establish direct peer-to-peer connections where possible, which can add latency
  • Client configuration and certificate management for the open source version is more manual and error-prone than newer VPN tools with zero-config onboarding
  • Access Server pricing above the Growth tier reverts to custom Enterprise quoting, so very large deployments lose the pricing transparency of the lower tiers
  • The protocol's throughput is generally lower than newer kernel-integrated protocols like WireGuard under equivalent conditions, which matters for high-bandwidth use cases

Pricing, plan by plan

Nebula

Free
  • NebulaFree
    • Full functionality under the MIT licence
    • No host limit
    • You operate the certificate authority and lighthouses
  • Defined Networking$undefined/month
    • Hosted control plane and enrolment
    • Managed certificate lifecycle and revocation
    • Policy and DNS interface

OpenVPN

Free
  • Access Server FreeFree
    • Up to 2 simultaneous connections
    • All features included
  • Access Server Growth$7/month
    • Per simultaneous connection beyond the free tier
    • Annual billing
  • Access Server Enterprise/IoT$undefined/month
    • Custom pricing for 2,000+ connections

Which should you pick?

Choose Nebula if

  • You need certificate carried identity.
  • You want to start without paying.
  • You work on Linux, macOS, Windows, iOS, Android, FreeBSD.
  • You also want group based host firewall.
Nebula review

Choose OpenVPN if

  • You need open source core.
  • You want to start without paying.
  • You work on Linux, Windows, macOS, iOS, Android.
  • You also want access server admin ui.
OpenVPN review

Questions people ask

Is Nebula or OpenVPN better?
Neither clearly leads. Nebula starts at Free and OpenVPN at Free, and user ratings are close enough to be indistinguishable. Choose on capability and platform support.
Which is cheaper, Nebula or OpenVPN?
Nebula starts at Free and OpenVPN at Free.
Does Nebula or OpenVPN run on more platforms?
Nebula runs on Linux, macOS, Windows, iOS, Android, FreeBSD. OpenVPN runs on Linux, Windows, macOS, iOS, Android.
Can I use Nebula for free?
Both have a free tier, so you can try either at no cost before committing.
What is Nebula best used for?
Nebula is most often used for flattening a network across several clouds and datacentres without vpc peering or route tables, very large fleets where a central policy service on the connection path is unacceptable, environments that already run an internal certificate authority and want the network to use it, replacing per host iptables rules with policy written against roles that follow the host. Of those, flattening a network across several clouds and datacentres without vpc peering or route tables and very large fleets where a central policy service on the connection path is unacceptable are not what OpenVPN is typically brought in for.
What can Nebula do that OpenVPN cannot?
Nebula covers Certificate carried identity, Group based host firewall, Lighthouse discovery, Noise protocol encryption. OpenVPN covers Open source core, Access Server admin UI, Per-connection licensing, Free tier.

Answered from the vendors’ own pages

Nebula: Does it use WireGuard?

No. Nebula predates the common WireGuard mesh tools and uses the Noise protocol framework with its own certificate format.

OpenVPN: Is OpenVPN free?

The open source protocol and software are free under the GPL; Access Server, the commercial packaged product, charges per simultaneous connection beyond a free 2-connection tier.

Nebula: Can I run it without Defined Networking?

Yes, entirely. Defined Networking sells the control plane conveniences, not the network itself.

OpenVPN: What counts as a connection for billing purposes?

A simultaneously active connected device, not a registered user account or total device count; unlimited accounts and devices can be created but only the licensed number can be connected at once.

Nebula: How do I revoke a host?

Add its certificate fingerprint to the blocklist in the configuration of the other hosts and reload them. There is no online revocation check.

OpenVPN: How does OpenVPN compare with WireGuard-based tools like Tailscale?

OpenVPN uses a traditional hub-and-spoke VPN architecture rather than the mesh, peer-to-peer approach used by newer tools like Tailscale or NetBird.

Nebula: Is it a good fit for laptops?

Less so than the identity provider based tools. There is no single sign on, so every laptop needs a certificate issued and renewed by whatever process you build.

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