View CER files in your browser
The certificate a website, a signer or an app maker proves who they are with. See everything in one, right here, without a terminal. Nothing leaves your device.
Or drop it anywhere on this page
What you'll see
Your certificate opens as a card: who it's for, who issued it, its dates and its chain.
- Its chain • Checked against the roots Filepeek carries
- Valid from and until • The days it has
- Every name it covers • Domains and emails
- SHA-256 and SHA-1 fingerprints • Copy with a click
About CER
X.509 certificates began with the ITU-T in 1988, and the IETF's profile of them runs the web's HTTPS, signed email, signed apps and Europe's qualified signatures. A CA signs each one to vouch that a key belongs to a name.
A .cer, .crt or .der holds one certificate, as DER bytes or as base64 text between BEGIN CERTIFICATE lines: who it's for, who issued it, when it's valid, the names it covers, its public key and what that key may do.
Filepeek shows it as a card: the subject and the issuer, its dates and the days it has, every name, the key's kind and size, its fingerprints to copy and where its CA answers about it. Its chain is checked against the roots Filepeek carries, and nothing is asked of a CA.
X.509 certificate
.cer • .crt • .der • .cert
Format
- MIME type
- application/pkix-cert
- Made by
- The ITU-T
- Released
- 1988
Inside the file
- Holds
- A name, a public key and a CA's signature
- Valid
- From one date until another
- Encoding
- DER, or base64 text
- Standard
- X.509
Opens in every browser
Browsers download certificate files. Filepeek shows one in Chrome, Edge, Firefox and Safari, without installing it.
- YouChromeOpens through Filepeek
- YouEdgeOpens through Filepeek
- YouFirefoxOpens through Filepeek
- YouSafariOpens through Filepeek
Questions
How do I see what's in a certificate?
Drop the .cer, .crt or .der on this page or press Peek a CER. Its subject, issuer, dates, names, key and fingerprints show at once.
Is a certificate safe to open?
Yes. A certificate holds only public facts and a public key. Filepeek reads it without installing it or trusting it.
What's the difference between CER, CRT and DER?
Only habit. Each holds a certificate, as DER bytes or as base64 text between BEGIN CERTIFICATE lines, and Filepeek reads both whatever the name.
Is my file uploaded?
No. The file opens inside your browser and never leaves your device.