OpenVPN vs SSTP

SSTP (Secure Socket Tunneling Protocol) is a Microsoft-developed VPN protocol introduced with Windows Server 2008. It tunnels PPP traffic over SSL/TLS. OpenVPN is the open-source cross-platform alternative. The comparison is mostly straightforward: OpenVPN wins on portability and openness; SSTP's main advantage is native Windows integration.

At a glance

	OpenVPN	SSTP
Released	2001	2007 (with Windows Server 2008)
Source	Open-source	Microsoft proprietary
Cross-platform	Yes (every major OS)	Native Windows; limited elsewhere
Codebase audit	Multiple public audits	Closed-source, no public audit
Transport	UDP or TCP	TCP (TLS over port 443)
Speed	Comparable	Comparable
Configurability	Extensive	Limited
Native iOS/Android support	Via OpenVPN Connect app	Limited third-party support

Why SSTP exists

Microsoft built SSTP to provide a VPN protocol that:

• Runs over TCP port 443 (looks like HTTPS to firewalls)
• Integrates natively with Windows authentication
• Uses TLS for encryption (familiar to Windows admins)
• Works in environments where IPsec is blocked

The native Windows integration is genuinely useful in Microsoft-heavy environments. Domain authentication, group policies, Windows Server VPN deployment — all integrate cleanly with SSTP. For Windows-only enterprise environments, SSTP can be the path of least resistance.

Why OpenVPN wins for most

OpenVPN does everything SSTP does plus more:

• Cross-platform. Linux, macOS, iOS, Android, FreeBSD, embedded systems all have OpenVPN clients. SSTP outside Windows has limited support; some third-party clients exist but are not mainstream.
• Open-source. The code is auditable. Multiple public audits over the years. SSTP is closed-source; the security review depends on Microsoft's internal processes which are not public.
• TCP-443 firewall bypass. OpenVPN-TCP-443 is the protocol-of-choice for firewall bypass on networks without active VPN-protocol DPI. Both OpenVPN-TCP-443 and SSTP look like HTTPS at the network layer; OpenVPN is more configurable.
• Wider community and tooling. Vastly more documentation, more troubleshooting resources, more compatibility matrices.

SSTP-specific issues

A few quirks:

• Closed protocol. Some specifics of SSTP's behaviour are documented only in Microsoft's protocol specifications, which are public but not easily consumed for independent implementation. A third-party SSTP client requires reverse-engineering or careful reading of Microsoft's specs.
• MS-CHAP-v2 historical weakness. Older SSTP configurations using MS-CHAP-v2 for authentication had significant cryptographic weaknesses (broken in 2012). Modern SSTP configurations use stronger authentication; legacy deployments may not.
• Limited mobile support. Native iOS and macOS do not include SSTP. Android has third-party SSTP clients of varying quality. The mobile story is meaningfully worse than OpenVPN's.

When SSTP makes sense

Specific situations:

• Windows-only enterprise environments. Active Directory authentication, Windows Server-based VPN, environments where the IT team is fluent in Windows but not in OpenVPN. SSTP integrates cleanly.
• Firewalls that allow HTTPS but block all known VPN protocols. SSTP runs over TCP 443 with TLS; some firewalls cannot distinguish it from HTTPS. OpenVPN-TCP-443 has the same property; SSTP's advantage is marginal.

For consumer VPN users, none of these applies. SSTP rarely appears on consumer VPN provider feature lists; when it does, it is usually a legacy holdover.

What Fexyn ships

Fexyn Secure is OpenVPN. We do not ship SSTP. No modern consumer VPN provider gains anything from offering SSTP that they do not get from OpenVPN-TCP-443.

Try Fexyn free for 7 days — Bolt (WireGuard) as default, Secure (OpenVPN) for compatibility, Stealth (Reality) for DPI-heavy networks.