sslyze
Fast and powerful SSL/TLS scanning library.
Decision gist · record as of 2026-08-14
Yes, with conditions. SSLyze is actively maintained, has no known vulnerabilities, and is well-suited for TLS auditing and compliance checking. However, the AGPL license is restrictive—proprietary projects must either accept copyleft obligations or avoid it. High install friction (native dependencies) may complicate deployment in some environments. Install if you need TLS scanning and can accept AGPL terms.AI-flagged interpretation of the facts on this page — verify before relying
Before you install
- Requires Python 3.10 or later.
- Native compilation dependencies (nassl, cryptography) must build successfully on your platform.
- High install friction due to compiled dependencies (nassl, cryptography, tls-parser).
License · maintenance · safety
AGPL (agpl) — SSLyze is licensed under AGPL, which requires that any modifications or derivative works using this library must also be released under AGPL. This is a copyleft license with strong reciprocal obligations; proprietary or closed-source projects should verify compatibility before depending on it.
last release 2026-03-29 (138 days) · last repo commit 2026-07-29 · 3,770 stars
0 known vulnerabilities (OSV.dev, 2026-08-14) · 127,082 downloads/mo, #11,754 on PyPI
Alternatives
Verify before relying
pip install sslyze
python -m sslyze www.example.com
# Or via Python API:
from sslyze import ServerScanRequest, Scanner
request = ServerScanRequest(hostname="www.example.com")
scanner = Scanner()
results = scanner.run(request)- Whether the AGPL license applies to indirect use (e.g., calling sslyze from a web service) and what derivative-work obligations that triggers
- Performance characteristics when scanning hundreds of thousands of servers as claimed in the description
What it is and what it does
SSLyze is a Python library and command-line tool for analyzing the SSL/TLS configuration of remote servers. It connects to a server, inspects its certificate, supported cipher suites, protocol versions, and elliptic curves, then reports on encryption strength and known vulnerabilities like Heartbleed, ROBOT, and OpenSSL CCS injection. It supports scanning non-HTTP servers including SMTP, XMPP, LDAP, POP, IMAP, RDP, Postgres, and FTP.
The tool is designed for both one-off security audits and continuous compliance checking. It can validate server configurations against Mozilla's recommended TLS profiles (old, intermediate, modern) or custom JSON-defined policies, making it suitable for CI/CD integration. Results can be exported to JSON for further processing. The library exposes a full Python API for embedding scans into applications, such as Lambda functions or custom security tools.
Use it for
- Audit a web server's TLS configuration to identify weak ciphers or outdated protocol versions before deployment.
- Run SSLyze as a CI/CD step to enforce Mozilla's modern TLS configuration and fail builds that don't comply.
- Scan SMTP or LDAP servers to verify they support strong encryption and are not vulnerable to known attacks.
- Build a security monitoring dashboard that periodically scans your organization's servers and exports results to JSON for alerting.
- Test a custom TLS policy by defining allowed certificate types, cipher suites, and versions in a JSON file and validating servers against it.
Worth the install?
AI-flagged interpretation of the facts on this page. Verify before relying on it.
Yes, with conditions.
SSLyze is actively maintained, has no known vulnerabilities, and is well-suited for TLS auditing and compliance checking. However, the AGPL license is restrictive—proprietary projects must either accept copyleft obligations or avoid it. High install friction (native dependencies) may complicate deployment in some environments. Install if you need TLS scanning and can accept AGPL terms.
Install
sslyze on PyPI
Before you install
High install friction due to compiled dependencies (nassl, cryptography, tls-parser). The package is actively maintained with recent releases and a stable repository, but setup requires building native extensions.
Requires Python 3.10 or later. Native compilation dependencies (nassl, cryptography) must build successfully on your platform.
License in practice
SSLyze is licensed under AGPL, which requires that any modifications or derivative works using this library must also be released under AGPL. This is a copyleft license with strong reciprocal obligations; proprietary or closed-source projects should verify compatibility before depending on it.
Quickstart
pip install sslyze
python -m sslyze www.example.com
# Or via Python API:
from sslyze import ServerScanRequest, Scanner
request = ServerScanRequest(hostname="www.example.com")
scanner = Scanner()
results = scanner.run(request)Verify before relying
- Whether the AGPL license applies to indirect use (e.g., calling sslyze from a web service) and what derivative-work obligations that triggers
- Performance characteristics when scanning hundreds of thousands of servers as claimed in the description
Package facts
| License | AGPL agpl |
| Python support | Supports the current Python release >=3.10 |
| Install friction | High. Source build required |
| Runtime dependencies | 4 packagesnasslcryptographytls-parserpydantic |
| Maintenance | Actively maintained 138 days since the last release |
| Last repo commit | |
| First released | |
| Downloads | 127,082 / month, #11,754 on PyPI 30-day window, as of 2026-08-14 |
| Known vulnerabilities | None known OSV.dev, checked 2026-08-14 |
| Classifiers | Development Status :: 4 - BetaIntended Audience :: DevelopersIntended Audience :: System AdministratorsLicense :: OSI Approved :: GNU Affero General Public License v3Natural Language :: FrenchProgramming Language :: Python :: 3.10Programming Language :: Python :: 3.11Programming Language :: Python :: 3.12Programming Language :: Python :: 3.13Programming Language :: Python :: 3.14Topic :: SecurityTopic :: System :: MonitoringTopic :: System :: NetworkingTopic :: System :: Networking :: Monitoring |
Evidence: sslyze-6.3.1.tar.gz
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See also nassl · tls-parser · secure-smtplib · django-sslserver · oscrypto · pip-system-certs · python-certifi-win32 · trustme · pyOpenSSL · python-nmap