X.509 / PEM Public Key Decoder
Paste a PEM-encoded public key (SPKI) to see its algorithm and key size. 100% in your browser.
v1 supports SPKI public keys only. Full X.509 cert parsing coming soon.
About X.509 / PEM Public Key Decoder
The X.509 / PEM Public Key Decoder reads a PEM-encoded public key and reports its details. Paste a key block that starts with the BEGIN PUBLIC KEY header and the tool parses the SubjectPublicKeyInfo structure, then shows the key algorithm, such as RSA or an elliptic curve, along with the key size in bits.
Decoding is done locally with the browser crypto APIs, so the key you paste is never transmitted. Public keys are not secret, but keeping the work in the browser means you can quickly check a key from a certificate or configuration file without relying on an outside server.
Frequently asked questions
- What key format does it accept?
- It accepts PEM-encoded SubjectPublicKeyInfo (SPKI) blocks beginning with the BEGIN PUBLIC KEY line.
- Can it decode a private key?
- No. The tool is built for public keys; private key material is not parsed.
- Which algorithms are recognized?
- Common public key algorithms including RSA and elliptic curve keys are identified along with their size.