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SSL Certificate Checker

Parse openssl x509 -text output for issuer, subject, SANs and validity dates, with warnings for expired certificates or ones expiring within 30 days.

SSL Certificate Checker

Output

Working…

Updated . Provided as is. Check the output before you rely on it in production.

How to use SSL Certificate Checker

  1. 1

    Get the certificate text

    Run openssl s_client -connect example.com:443 | openssl x509 -noout -text, or paste PEM details from your certificate tooling.

  2. 2

    Paste it

    Paste the output, or load the sample.

  3. 3

    Read the details

    Issuer, subject, validity dates, days remaining and the DNS names in the Subject Alternative Name list are extracted.

  4. 4

    Act on the warnings

    Expired certificates and certificates that expire within 30 days are flagged.

Questions and answers

Does it connect to my server?
No. It parses certificate text you paste, so it also works for internal hosts.
Why check the SAN list?
Browsers match the hostname against the Subject Alternative Names, not the common name. A missing hostname there causes certificate errors.

Use it as an API

SSL Certificate Checker is also callable as a free HTTP JSON API at https://aidevhub.io/api/ssl-checker/ — GET with query parameters or POST with a JSON body, no authentication, CORS enabled, fair use (abusive traffic is throttled at the edge; there is no per-request quota header). Responses return { ok, tool, result, meta }. 

curl -s -X POST https://aidevhub.io/api/ssl-checker/ \
  -H "Content-Type: application/json" \
  -d '{"certificate":"subject=CN = example.com\nissuer=CN = R3\nNot Before: Jan  1 00:00:00 2026 GMT\nNot After : Jan  1 00:00:00 2027 GMT\nX509v3 Subject Alternative Name: DNS:example.com, DNS:www.example.com"}'

Machine-readable contract: /api/tool/ssl-checker.json All API endpoints: /agents/ LLM site index: /llms.txt

For AI agents: how to call this tool

Machine-readable contract, endpoints and examples. Humans can ignore this section.

Best Path For Builders

Dedicated API endpoint

Deterministic outputs, machine-safe contracts, and production-ready examples.

Dedicated API

https://aidevhub.io/api/ssl-checker/

OpenAPI: https://aidevhub.io/api/openapi.yaml

GET /api/ssl-checker/ GET ssl-checker
POST /api/ssl-checker/ POST ssl-checker

Unified Runtime API

https://aidevhub.io/api/tools/run/?toolId=ssl-checker&a=subject%3DCN%20%3D%20example.com%0Aissuer%3DCN%20%3D%20R3%0ANot%20Before%3A%20Jan%20%201%200

GET and POST are supported at /api/tools/run/ with identical validation and limits.

Limit: 10 req / 60s, input max 512 KB.