SSL & TLS Tools for Developers
6 free SSL/TLS tools — decode CSRs and certificates, generate openssl commands, build nginx / Apache / HAProxy SSL configs. We never generate private keys in the browser — the right way is to run openssl locally so the key never leaves your server.
OpenSSL Command Generator
Visual builder for OpenSSL commands — generate the exact CSR + private key command to run on your server.
CSR Decoder
Decode and inspect PEM-encoded Certificate Signing Requests — see Common Name, SANs, key info, signature.
SSL Certificate Decoder
Decode and inspect PEM SSL/TLS certificates — issuer, subject, validity, SANs, fingerprint, key details.
Self-Signed Cert Command Generator
Visual builder for OpenSSL self-signed certificate commands — for dev environments, local HTTPS, and testing.
SSL Config Generator
Generate nginx, Apache, HAProxy, and Lighttpd SSL/TLS config snippets — Modern, Intermediate, or Old profiles.
DH Parameters Command Generator
Generate the OpenSSL command for Diffie-Hellman parameters — required for older nginx/Apache TLS configs.
Browse by Category
⚠️ Why we do not generate private keys in your browser
Most online "SSL generators" ask you to generate a private key in their website. Don't. A compromised page, a malicious browser extension, or a JavaScript supply-chain attack would leak your key — and you would never know until traffic was decrypted. The right way is to generate the key on the server that will use it, so it never crosses a network. Our tools generate the openssl command for you to run locally.
Why use OpenFormatter for SSL?
No private key risk
Decoders parse public information only. Command generators emit text — you run openssl on your own machine. We have no way to ever see a key.
Education first
Each tool explains the openssl flags used, the security trade-offs, and links to the relevant RFC and Mozilla guidance.
Mozilla-based config
SSL Config Generator follows the Mozilla SSL Configuration Generator methodology — Modern / Intermediate / Old profiles for nginx, Apache, HAProxy, Lighttpd.
Browser-side parsing
CSR and certificate decoders run entirely in the browser using a small ASN.1 parser — no upload, no rate limit.
Frequently Asked Questions
Why do you not generate private keys in the browser?
Generating real private keys in a browser puts users at risk: the page could be compromised, browser extensions can read memory, and people may use the key for production by mistake. Industry best practice (DigiCert, Sectigo, Mozilla) is to generate private keys on the machine that will use them. Our tools generate the openssl command for you to run locally — your private key never leaves your server.
Are CSR Decoder and Certificate Decoder safe to use?
Yes — these are read-only parsers. They take an existing PEM CSR or certificate (which is public information by design — certificates are sent over the wire to every TLS client) and display its contents. The parsing happens in your browser; nothing is uploaded.
What is the difference between a CSR and a certificate?
A CSR (Certificate Signing Request) is what you send to a Certificate Authority to request a certificate. It contains your public key and the identity you want certified (Common Name, SANs, etc.). The CA validates your identity and signs a certificate which it returns to you. The CSR is throw-away once you have the certificate.
What is the OpenSSL command to generate a CSR?
openssl req -new -newkey rsa:2048 -nodes -keyout server.key -out server.csr -subj "/C=US/ST=California/L=San Francisco/O=Acme Inc/CN=example.com". This generates a 2048-bit RSA private key (server.key) and a CSR (server.csr). Use the OpenSSL Command Generator for a visual builder with SAN support.
Should I use RSA or ECDSA for my SSL certificate?
For new deployments use ECDSA P-256 — it is faster, smaller, and as secure as RSA 3072. RSA 2048 is the safe default if your CA does not support ECDSA or you need maximum compatibility (ancient clients). Avoid RSA below 2048 (deprecated) and avoid ECDSA P-521 unless you specifically need it (poor performance).
What is the right TLS profile for my server?
Use Mozilla's recommendations: Modern (TLS 1.3 only — for sites with no legacy clients), Intermediate (TLS 1.2 + 1.3 — the right default for most sites), or Old (back to TLS 1.0/1.1 — only if you must support Windows XP / IE 6). Our SSL Config Generator implements all three Mozilla profiles for nginx, Apache, HAProxy, and Lighttpd.
Do I still need DH parameters in 2026?
For TLS 1.3-only configurations (Modern profile), no — TLS 1.3 does not use DH parameters. For TLS 1.2 with DHE cipher suites (Intermediate/Old), nginx and Apache need a dhparam file or they fall back to a weak default. ssl_dhparam (nginx) and SSLOpenSSLConfCmd DHParameters (Apache) point to the file. Use 2048 bits at minimum, 4096 for forward-looking deployments.
Where can I get a free real SSL certificate?
Use Let's Encrypt with the certbot ACME client. Generate the CSR (or let certbot do it), validate domain ownership via HTTP or DNS challenge, and get a 90-day cert renewable automatically. Cloudflare also offers a free Universal SSL plus Origin certificates for backend traffic.
Need other developer tools?
Pair the SSL tools with the rest of OpenFormatter — 200+ tools, all browser-side.