How to read a .P7S file online
Three steps, a few seconds.
Open your .P7S 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 .P7S file?
What's inside .crt, .pem and .p12 files, in plain words.
A P7S file, usually named smime.p7s, is the digital signature attached to a signed email. It proves the sender's identity and that the message was not altered in transit. You normally do not open it yourself; an S/MIME-capable mail client (Outlook, Apple Mail, Thunderbird) reads it automatically and shows a "signed" badge. The file appears as a stray attachment only when your mail app cannot process S/MIME.
Programs that open .P7S files
| Full name | PKCS #7 / S/MIME Digital Signature (smime.p7s) |
|---|---|
| Developer | RSA Security (PKCS #7); standardized by IETF as CMS (Cryptographic Message Syntax) / S/MIME |
| First released | PKCS #7 v1.5 (1993, RSA); S/MIME v2 RFC 2311 (1998); CMS RFC 5652 (2009) |
| Category | Data & Other |
| MIME type | application/pkcs7-signature |
| Signature | 30 82 (DER-encoded form starts with an ASN.1 SEQUENCE: 0x30 0x82 (length bytes follow). PEM form is Base64 text beginning "-----BEGIN PKCS7-----". No human-readable content.) |
Related viewers
Other free tools to open and preview your files.
Frequently asked questions
Is it safe to open my .P7S 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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