How to read a .CRT file online
Three steps, a few seconds.
Open your .CRT file
Drop it on the box or click to choose it. A bundle holding several certificates is split for you automatically.
Unlock if needed
A password-protected file asks for its export password. It is used only to unlock the file.
Check the details
Read the chain from your certificate up to the root, see every domain it covers, when it expires and copy its SHA-256 fingerprints.
What is a .CRT file?
What's inside .crt, .pem and .p12 files, in plain words.
A CRT file is an X.509 digital certificate that ties an identity (a website, server, or publisher) to a public key, signed by a Certificate Authority. On Windows, double-click it to view the issuer, validity dates, and purpose, then install it into the certificate store if needed. It holds only a public key, is safe to view and share, and cannot execute code.
Programs that open .CRT files
| Full name | Security certificate (X.509 .crt) |
|---|---|
| Developer | ITU-T / IETF (X.509 PKI standard); the .crt convention is common on Unix/Linux and web servers |
| First released | X.509 first published 1988 (ITU-T); .crt is a long-standing certificate extension on Unix/Apache |
| Category | Data & Other |
| MIME type | application/x-x509-ca-cert |
| Signature | 30 82 (DER-encoded .crt starts with ASN.1 SEQUENCE: 0x30 0x82 . PEM-encoded .crt starts with text '-----BEGIN CERTIFICATE-----') |
Related viewers
Other free tools to open and preview your files.
Frequently asked questions
Is it safe to open my .CRT file here?
Yes. Certificates are public by design, and decoding and signature checks run with the Web Crypto API.
What does “chain verified” mean?
Each certificate is signed by the one above it. The viewer checks those signatures mathematically, so you can see whether your server certificate, intermediate and root actually belong together - the most common cause of “incomplete chain” errors.
My .p12 / .pfx asks for a password. Which one?
The password chosen when the file was exported (for example from Windows, a browser or your CA's portal). Some files have an empty password - try leaving the field blank.
Why don't you show my private key?
A private key is the secret half of the certificate. Anyone who sees it can impersonate you, so the viewer only tells you that a key is present and what type and size it is.
Can it check if a certificate is revoked?
Not yet. Revocation (OCSP/CRL) needs to contact the certificate authority, which we keep for the server-side version of this tool.
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