Inspect SSL certificates to debug expiration, hostname mismatch, chain issues, issuer changes, and HTTPS rollout problems.
HTTPS problems can appear as browser warnings, failed API calls, webhook errors, mobile app failures, or broken domain launches. The certificate is often the first place to inspect because it explains identity, validity dates, issuer, and hostnames.
An SSL certificate parser helps read certificate details without staring at raw encoded blocks. It turns a dense certificate into fields you can check systematically.
The certificate must cover the hostname being requested. A certificate for example.com may not cover api.example.com unless the subject alternative names include it or a wildcard applies correctly.
Hostname mismatch is common during migrations, staging setup, CDN changes, and API subdomain launches. Always inspect the exact hostname users or systems call.
Expired certificates create urgent failures. Certificates that are not valid yet can also break systems if clocks or deployment timing are wrong. Inspect not before and not after dates and convert times when needed.
For incident notes, pair certificate dates with a timestamp converter. This helps explain exactly when the certificate became invalid.
Browsers and clients need a trusted chain from the site certificate to a trusted root. Missing intermediate certificates can cause failures in some clients while others appear fine because they cached intermediates.
If only certain clients fail, inspect the chain carefully. Mobile apps, older systems, and strict API clients can expose chain problems that desktop browsers hide.
Unexpected issuer details can reveal that the wrong certificate was deployed, a staging certificate reached production, or a CDN is serving a default certificate. Check issuer, subject, and alternative names together.
During domain launches, combine certificate inspection with a DNS propagation checker. DNS may point some users to an old endpoint with an old certificate.
Wildcard certificates have limits. A wildcard for *.example.com typically covers app.example.com but not deep.app.example.com. Do not assume every subdomain is covered.
List the actual hostnames your application, API, assets, and webhooks use. Then confirm certificate coverage for each one.
Certificate problems are often process problems. Know who owns renewal, where certificates are managed, what automation exists, and how alerts are delivered. Add renewal checks before expiration becomes an incident.
For critical domains, test renewal automation and monitor certificate expiry externally. One missed renewal can take down a major user path.
Certificate parsing explains one part of HTTPS. If the certificate looks correct, continue with DNS, redirects, HTTP headers, firewall rules, and application behavior.
Clear certificate details turn a scary browser warning into a checklist. Hostname, dates, chain, issuer, and environment usually tell you where to look next.
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