Stunnel is an open-source multi-platform application used to provide a universal TLS/SSL tunneling service.
Stunnel is used to provide secure encrypted connections for clients or servers that do not speak TLS or SSL natively. It runs on a variety of operating systems, including most Unix-like operating systems and Windows. Stunnel relies on the OpenSSL library to implement the underlying TLS or SSL protocol.
Stunnel uses public-key cryptography with X.509 digital certificates to secure the SSL connection, and clients can optionally be authenticated via a certificate.
If linked against libwrap, it can be configured to act as a proxy–firewall service as well.
Stunnel is maintained by Polish programmer Michał Trojnara and released under the terms of the GNU General Public License (GPL) with OpenSSL exception.
A stunnel can be used to provide a secure SSL connection to an existing non-SSL-aware SMTP mail server. Assuming the SMTP server expects TCP connections on port 25, the stunnel would be configured to map the SSL port 465 to non-SSL port 25. A mail client connects via SSL to port 465. Network traffic from the client initially passes over SSL to the stunnel application, which transparently encrypts and decrypts traffic and forwards unsecured traffic to port 25 locally. The mail server sees a non-SSL mail client.
What is Stunnel?
Stunnel by Michał Trojnara is open-source Windows software in the vpn & proxy category. Besides Windows, it is available for Unix-like operating system.
Installation and requirements
The publisher provides EXE (NSIS) installers for 64-bit Windows. The main installer is 4.0 MB. Installation asks for administrator rights. A silent install is possible with the installer’s documented switches.
Updates and version history
The current version is 5.82, released on September 17, 2026. The version history goes back to October 18, 2025: 7 releases, all linked to the official files.
Popularity and file types
Wikipedia has an article about it in 11 of our languages. Similar programs include nginx, OpenVPN and Proton VPN.
Pros / Cons
Pros
- Open source: the code can be inspected and built by anyone
- Documented silent install
- Updated in the last two months
- Small download (4.0 MB)
- Also runs on Unix-like operating system
Cons
- No native ARM64 build
- Installation needs administrator rights
In short: Stunnel is an open-source vpn & proxy tool for 64-bit PCs. Administrators can deploy it unattended.
Is Stunnel safe to download?
- The file is served by stunnel.org, the publisher’s own domain
- The download link uses HTTPS
- A SHA256 hash is published, so you can verify the file:
722C1AD626919AF2B0034666B4D19CC4795E925C32F60E8F3C59AF4FB3AD2DFC· Open the VirusTotal report for this hash - The link answered when we last checked it (October 22, 2026)
- The source code is public
- ExeAtlas does not host, wrap or modify installers
Related guide: How to check a file’s SHA256 hash on Windows
Recent versions
All 7 versions ›| Version | Date | Size | Files |
|---|---|---|---|
| 5.82Latest | September 17, 2026 | 4.0 MB | 64-bit EXE (NSIS) |
| 5.81 | September 16, 2026 | — | 64-bit EXE (NSIS) |
| 5.80 | August 4, 2026 | — | 64-bit EXE (NSIS) |
| 5.79 | June 29, 2026 | — | 64-bit EXE (NSIS) |
| 5.78 | April 9, 2026 | — | 64-bit EXE (NSIS) |
| 5.77 | February 17, 2026 | — | 64-bit EXE (NSIS) |
| 5.76 | October 18, 2025 | — | 64-bit EXE (NSIS) |
Install from the command line
Silent install ›winget install --id MichalTrojnara.Stunnel -escoop install extras/stunnelstunnel-5.82-win64-installer.exe /SProgram files (.exe): stunnel.exe
Related guide: How to use winget: install and update apps
Also for other systems
brew install stunnelInformation
- Publisher
- Michał Trojnara
- Category
- VPN & proxy
- Licence
- GPL-2.0
- Price
- Free
- Requires
- Windows 11 / 10
- Architecture
- 64-bit
- Installer
- EXE (NSIS)
- Other platforms
- Unix-like operating system
- Version
- 5.82
- Released
- September 17, 2026
- Added to the catalogue
- October 18, 2025
- Versions listed
- 7
- Website
- stunnel.org
- winget ID
- MichalTrojnara.Stunnel
- Scoop package
- extras/stunnel
Ratings and reviews
No reviews yet. Be the first to rate it.
Alternatives to Stunnel
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Frequently asked questions
Is Stunnel free?
Yes. Stunnel is open-source software under the GPL-2.0 licence.
Is Stunnel safe to download?
The download comes from stunnel.org, which belongs to the publisher; ExeAtlas does not host or change the file. Compare its SHA256 hash with the one shown here, or open the VirusTotal report for that hash.
How do I install Stunnel with winget?
Open PowerShell or Windows Terminal and run the winget command shown on this page. winget downloads the official installer and checks its SHA256 hash before running it.
Can Stunnel be installed silently?
Yes. The silent install page lists the exact command for each installer.
Does Stunnel run on ARM (Windows on Arm)?
There is no ARM64 build; Windows 11 on Arm can run the 64-bit version through emulation.
Where can I download an older version of Stunnel?
The versions page lists all 7 versions with links to their official installer files, back to October 18, 2025.
What are alternatives to Stunnel?
nginx, OpenVPN, Proton VPN, Tailscale and Netbird. The alternatives page compares them.
