Certificate commands that actually work
Every OpenSSL command you need for TLS certificates — generate, convert, inspect, fix. Each one is tested before it goes live, so it works when you paste it.
The five you probably came for
openssl x509 -in certificate.crt -noout -textopenssl x509 -in certificate.crt -noout -enddateopenssl req -new -newkey rsa:2048 -nodes -keyout site.key -out site.csropenssl s_client -connect example.com:443 -servername example.com </dev/nullopenssl pkcs12 -export -out cert.pfx -inkey site.key -in site.crtBrowse by what you are doing
- 19 pages
OpenSSL Commands
Every common OpenSSL invocation for keys, CSRs, certificates and certificate authorities, with the flags explained.
- 12 pages
Certificate Format Conversion
Convert certificates and keys between PEM, DER, PKCS#7, PKCS#12 and Java keystores.
- 9 pages
Certificate File Formats
What PEM, DER, CRT, CER, KEY, CSR, P7B, PKCS#8, PFX and JKS files actually contain, and how to tell them apart.
- 16 pages
Certificate Errors
Diagnose and fix the certificate errors you actually hit, matched by their exact error string.
- 7 pages
Install Certificates by Platform
Install and configure TLS certificates on nginx, Apache, IIS, Tomcat, Kubernetes, HAProxy and more.
- 11 pages
Certificate Concepts
Chains of trust, CSRs, SANs, key usage, mTLS, revocation — the ideas behind the commands.
Decode things without uploading them
The tools here parse certificates, CSRs and keys entirely inside your browser. Nothing you paste is uploaded, logged or stored — and the tool pages ship a Content Security Policy that blocks network requests outright, so that is enforced rather than promised.
Why you can trust these commands
Certificate documentation rots quickly. OpenSSL 3.0 changed defaults that most published guides still get wrong, which is why so many of them produce files that Windows and Java silently refuse.
So every command here is run automatically before it is published. If one stops working, publishing stops with it — a broken command cannot reach the page you are reading.