testssl.sh, SSL Labs, or sslyze: which TLS scanner fits which job?

testssl.sh, SSL Labs, or sslyze: which TLS scanner fits which job?

Which tool should audit your TLS configuration? Three dominate, and they differ in vantage point, automatability, and depth — not in basic correctness.

SSL Labs (the Qualys server test) runs from Qualys's infrastructure against a public hostname. It is the canonical grading reference and excellent for an external view, but it cannot reach internal endpoints, rate-limits, and returns a grade rather than a machine-friendly result.

testssl.sh is a local bash script. It runs from wherever you put it — including inside a network against private hosts — checks protocol versions, cipher suites, and a long list of named vulnerabilities, and emits JSON/CSV for pipelines. It is the field tool.

sslyze is a Python library and CLI built for programmatic scanning at scale, with structured output and fast concurrent connection analysis — the right choice when scanning is part of automated infrastructure.

— Use SSL Labs for an authoritative external grade on public hosts.
— Use testssl.sh for ad-hoc internal audits and vulnerability name-checks.
— Use sslyze when scanning must be embedded in code or run across a fleet.

Further reading: the SSL Labs methodology document; testssl.sh and sslyze project docs.

Bottom line: pick by vantage and automation — SSL Labs for external grading, testssl.sh for hands-on internal checks, sslyze for programmatic scale.