Intermediate certificates
Intermediate certificates sit between your website certificate and a trusted root certificate. Your server usually needs to send them during the TLS handshake.
SSL certificate decoder
SSL Certificate Checker and PEM Decoder
Paste your SSL certificate or full certificate chain in PEM format to decode certificate details and check issuer, validity dates, SANs, serial number, signature algorithm, public key type, and intermediate certificate information.
PEM decoderRead one public certificate or a full chain.
Chain hintsSee whether only a server certificate or intermediates are present.
No private keysPrivate keys are rejected and should never be pasted online.
What can this SSL certificate checker decode?
This tool decodes a pasted PEM certificate or certificate chain in your browser and displays identity, issuer, validity period, Subject Alternative Names, serial number, signature algorithm and fingerprints. It analyzes certificate data; it does not prove that a remote server is currently serving the same certificate.
Decode SSL certificate
You can paste a single server certificate or multiple PEM certificate blocks. Only paste public certificates.
Certificate result
Decoded certificate details will appear here.
What is an SSL Certificate Decoder?
An SSL Certificate Decoder is a tool that reads a pasted PEM SSL/TLS certificate and displays useful information in a readable format. Instead of manually reading raw certificate data, you can paste the public certificate and quickly check details such as common name, subject alternative names, issuer, validity period, serial number, public key type, signature algorithm, and certificate chain information.
This is useful for system administrators, network engineers, DevOps teams, website owners, CDN users, firewall administrators, and anyone troubleshooting HTTPS or TLS certificate issues. It can help you confirm whether a certificate is issued for the correct domain, whether it is expired, which Certificate Authority issued it, and whether expected SAN entries are present.
Certificate chain basics
Certificate chain
A certificate chain is the ordered trust path from the server certificate through one or more intermediate CA certificates to a trusted root certificate.
Missing intermediate?
If the checker shows only a server certificate, use the Certificate Chain Composer to fetch intermediates and build fullchain.pem.
What should I paste into this tool?
Paste a certificate in PEM format. A PEM certificate starts with -----BEGIN CERTIFICATE----- and ends with -----END CERTIFICATE-----. You can paste one certificate or multiple certificates together. If you paste a full chain, each certificate block should have its own BEGIN and END certificate lines.
Never paste your private key into any online certificate checker or decoder. A private key is sensitive and must remain protected on your server. This tool only needs the public certificate. If your private key is exposed, replace the certificate immediately.
SSL Certificate Decoder vs Certificate Chain Composer
Use the SSL Certificate Decoder when you want to decode and inspect pasted certificate details. It is the right page for checking SAN entries, issuer names, validity dates, fingerprints, public key information, and whether a pasted chain appears to include intermediate certificates.
Use the Certificate Chain Composer when you have a valid server certificate but are missing the intermediate certificates required to build a complete chain. The checker helps you understand what is inside the certificate, while the composer helps you build the correct full chain for installation.
Certificate Checker FAQ
Can this decode a full chain?
Yes. Paste multiple PEM certificate blocks and the tool will show each certificate separately with type, issuer, validity, fingerprint, and chain hints.
Does it generate intermediates?
No. This page decodes and checks certificates. Use the Certificate Chain Composer when you want to fetch missing intermediate certificates and build a full chain.
What is chain status?
Chain status is a practical warning that tells you whether a server certificate, intermediate certificate, root certificate, expired certificate, or not-yet-valid certificate was detected.
Certificate Checker: Working tool
This page includes a working interactive tool or quiz. Use the input, buttons, or quiz controls above to run the check, conversion, lookup, decoder, composer, or practice test directly in the browser.
Certificate Checker: Short intro
This tool is designed for fast networking practice and troubleshooting. It gives you a practical starting point, then the supporting notes below explain what to enter, what result to expect, and how to avoid common mistakes.
Certificate Checker: Example input/output
Example input: enter a valid value for the tool, paste supported certificate text, type a public IP or hostname, convert an epoch timestamp, or answer the displayed quiz question.
Example output: the page returns decoded details, converted time, lookup information, generated chain text, or a quiz result that can be used for study and troubleshooting.
Certificate Checker: Common errors
- Using the wrong input format for the selected tool.
- Pasting private or sensitive information when only public data is required.
- Reading approximate lookup or quiz results as a final diagnosis without checking the related configuration, logs, or command output.
Certificate Checker: Use cases
- Quickly validate networking concepts before a lab, exam, or interview.
- Support troubleshooting by converting, decoding, checking, or looking up technical values.
- Compare results with related tools and full practice tests for deeper review.
Certificate Checker: FAQ
Is this page interactive?
Yes. The working tool or quiz is available in the main section of the page.
Can I use it for troubleshooting?
Yes. Use it for quick checks, then confirm important findings with device commands, logs, or authoritative records.
Does it replace a full lab?
No. It is a fast helper or practice page. Use the related tools and labs for complete validation.