SSL & Certificate Tools - Free Online SSL Checker, CSR Generator & Decoder
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SSL & Certificate Tools
A properly installed SSL certificate is the difference between a browser showing a padlock and a browser showing a security warning. Misconfigured chains, mismatched keys, and expired certificates are among the most common causes of HTTPS errors, and most of them are invisible until a visitor (or a monitoring alert) hits them first. This hub brings together free, browser-based tools to check, generate, decode, and convert SSL certificates and CSRs — no command-line OpenSSL required. Need a certificate issued right now, with no CA account or CSR paperwork? Use the Free SSL Certificate Generator to get a real, browser-trusted certificate from Let's Encrypt in minutes — it now covers domains, wildcards, and even bare IP addresses.
SSL Diagnostic Tools
Start here if a site is showing a certificate warning, a mixed-content error, or you simply want to confirm an installation is correct before it goes live. Use the SSL Checker to scan a live domain's certificate chain and expiry, the Certificate Decoder to read the raw fields inside a PEM/CRT file, and Check CSR to validate a Certificate Signing Request before submitting it to a certificate authority.
CSR & Certificate Management Tools
When it's time to request, verify, or migrate a certificate, these tools handle the paperwork. CSR Generation creates a new Certificate Signing Request and private key pair, CSR Decoder reads back the details encoded in an existing CSR, Certificate Key Matcher confirms a certificate and private key actually belong together (a common cause of "SSL_ERROR" on servers), and SSL Converter converts between formats like PEM, DER, P7B, and PFX for different server software. Before requesting a new certificate, run DCV Checker to confirm your domain is ready for validation.
The Complete SSL Management Workflow
Follow this order when issuing a brand-new certificate from scratch, or jump to whichever step matches your current problem:
- Check domain readiness. Before requesting anything, run DCV Checker to confirm your CAA records and HTTP-01 challenge path won't block Domain Control Validation — catching this now avoids a failed or delayed issuance later.
- Generate your CSR (or skip this entirely). Use CSR Generation to create a new Certificate Signing Request and private key, then submit the CSR text to your certificate authority — or, if you don't already have a paid CA account, use the Free SSL Certificate Generator instead, which skips the CSR/CA-submission process entirely and issues a free Let's Encrypt certificate directly.
- Verify the CSR before submitting. Run it through Check CSR or CSR Decoder to confirm the CN, organization, key size, and SANs are correct — fixing a mistake here is much cheaper than reissuing after the CA has already signed it.
- Match your key to your certificate. Once the CA issues your certificate, run Certificate Key Matcher to confirm the certificate and private key actually pair together — this is the single most common cause of failed server deployments.
- Convert to the right format. If your hosting control panel or server expects a different file format, use SSL Converter to convert between PEM, DER, PFX/P12, and P7B.
- Inspect and verify. Paste any certificate or CSR into Certificate Decoder to see its decoded subject, issuer, validity dates, and SANs, then run SSL Checker against the live domain to confirm the installation resolves cleanly end-to-end. For a broader check beyond just the certificate — security headers, cookie flags, exposed files — run the Website Security Checker.
Usage Notes
- Private keys generated by CSR Generation are sensitive credentials — store them securely and never share them outside your own infrastructure.
- Certificates typically expire after 90 days to 1 year depending on the issuer; set a calendar reminder or use automated renewal (e.g. Let's Encrypt/ACME) to avoid unexpected outages.
- A certificate can be valid and still fail to load correctly if the chain is incomplete — always test with SSL Checker after installing on a server.
Frequently Asked Questions
What is a CSR?
A Certificate Signing Request (CSR) is a block of encoded text containing your domain and organization details plus a public key, which you submit to a Certificate Authority (CA) to request an SSL certificate. It's generated alongside a matching private key that must be kept secret.
Why does my browser still show "Not Secure" after installing an SSL certificate?
This usually means the certificate chain is incomplete (missing intermediate certificates), the certificate doesn't match the domain, or there's mixed content (HTTP resources loaded on an HTTPS page). Run the SSL Checker to identify the specific issue.
How do I know if a certificate and private key match?
Use the Certificate Key Matcher tool — it compares the public key embedded in the certificate against the private key and confirms whether they're a valid pair.
What's the difference between PEM, DER, and PFX formats?
PEM is Base64-encoded text (most common on Linux/Apache/Nginx), DER is binary-encoded, and PFX/P12 bundles the certificate and private key together in one password-protected file (common on Windows/IIS). Use SSL Converter to switch between them.
Are these SSL tools free to use?
Yes, all SSL and certificate tools on this page are free with no signup required.
Is it safe to paste my private key into an online tool?
Processing happens in your browser session and isn't stored, but as a general security practice, avoid pasting production private keys into any third-party tool when it can be avoided — generate new keys for testing when possible.
Can I get a free SSL certificate without a CSR or CA account?
Yes. The Free SSL Certificate Generator issues a real, browser-trusted certificate directly from Let's Encrypt — no CSR, no paid CA account, and no signup. It covers domains, wildcard domains, and (a newer capability) bare public IP addresses.
Learn More From Our Blog
Want the full walkthrough behind any of these tools? These guides go deeper into the how and why:
- What is SSL? The Complete Guide to SSL/TLS Certificates & HTTPS
- The Ultimate Guide to SSL/TLS: Why It Matters for SEO and How to Manage It
- SSL Certificate Checker: Verify Your SSL Online Free
- Certificate Decoder: Read SSL Certificate Details
- SSL Key Mismatch: Check If Certificate Matches Key
- CSR Generator: Create Certificate Signing Requests
- CSR Decoder: Decode & Verify CSR Files Online
- CSR Checker: Verify & Decode Your CSR Online Free
- SSL Certificate Converter: Convert PEM, DER, PFX
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