X.509 Certificate Parser for PEM Certificate Details
The X.509 certificate parser reads a PEM-encoded certificate in your browser using a built-in ASN.1/DER parser, so you do not need openssl. It displays the subject and issuer distinguished names, serial number, signature and public-key algorithms, validity dates and expired status, SHA-256 fingerprint, subject alternative names, and extensions. Paste or drop a certificate, inspect its fields, and copy the details you need.
The X.509 certificate parser turns a PEM-encoded certificate into a readable view of its contents. It uses a built-in ASN.1/DER parser in your browser, so you can inspect certificate details without needing openssl or manually reading the encoded text. The parser displays the subject and issuer distinguished names, serial number, signature and public-key algorithms, validity window, SHA-256 fingerprint, subject alternative names, and extensions.
To read the certificate, the tool parses its ASN.1/DER data and presents the information as named fields. The validity window includes an expired badge, while the extension list and subject alternative names help make those certificate details easier to find. Paste or drop a certificate, review the parsed view, and copy the information you need; the tool does not list configurable parsing options.
PEM is a text-based encoding used to represent certificate data, while DER is a binary encoding of ASN.1 data. This tool accepts PEM-encoded X.509 certificates and parses the underlying certificate structure into fields, rather than converting a certificate into another file format. A readable view can be more convenient than inspecting encoded text when checking TLS certificates, code-signing certificates, or related material.
The parser runs entirely in your browser: certificate input is processed on your device and is not uploaded, stored, or sent to a server. It works offline once the page has loaded, and the tool is free to use. Developers, DevOps engineers, and anyone reviewing a certificate can use it to inspect key fields without command-line tools.
Step 1: Paste or drop a PEM-encoded X.509 certificate into the tool. This is the certificate format the parser reads.
Step 2: Review the parsed certificate details. The view includes the subject and issuer distinguished names, serial number, and signature and public-key algorithms.
Step 3: Check the validity window and certificate identifiers. The parser shows validity dates, an expired badge, the SHA-256 fingerprint, and subject alternative names.
Step 4: Inspect the extensions, then copy the details you need. You can use the parsed information without reading the certificate’s encoded contents manually.
Use case: Inspect an X.509 certificate you did not create and cannot easily read. The parsed view makes its subject, issuer, validity, and other key details easier to review.
Use case: Check a TLS certificate’s validity window and expired status. This helps you quickly see whether the certificate is marked as expired.
Use case: Review the subject alternative names on a certificate. This is useful when checking which names the certificate lists.
Use case: Examine a code-signing certificate without using command-line tools. The parser displays its algorithms, fingerprint, and extensions in a readable view.
Use case: Look up a certificate’s serial number, issuer, or SHA-256 fingerprint. Copy the specific value you need for notes or further investigation.
Use case: Inspect certificate extensions when reviewing an unfamiliar PEM-encoded certificate. The tool presents the extension list alongside the other parsed fields.