How to use
- Paste PEM certificates or open a PEM / DER certificate file.
- Select a certificate and inspect its fields, dates and extensions.
- Copy a fingerprint or download PEM, DER or the JSON report.
Certificate Decoder
Paste one or more PEM certificates, or use Open PEM / DER for a certificate file. Select a certificate from the bundle to inspect its subject, issuer, serial number, public-key algorithm and signature algorithm.
Processing stays in your browser. DevToolsy does not receive the pasted data or selected file.
Input and processing
Review subject alternative names, CA constraints, key usages and raw extension OIDs. SHA-256 and SHA-1 fingerprints are calculated from the DER certificate bytes. Export the selected certificate as PEM or DER, or the bundle report as JSON.
-----BEGIN CERTIFICATE-----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-----END CERTIFICATE-----
{
"subject": "CN=example.test, O=DevToolsy Example, C=US",
"issuer": "CN=example.test, O=DevToolsy Example, C=US",
"san": [
{
"type": "dns",
"value": "example.test"
},
{
"type": "dns",
"value": "*.example.test"
},
{
"type": "ip",
"value": "192.0.2.1"
}
],
"sha256": "C0:F3:0D:4E:C5:E0:57:71:41:06:EA:5A:27:12:73:06:E9:57:DF:8F:FC:56:63:C3:6E:6B:77:DA:94:64:07:F4"
}This example uses the default settings.
Result and limitations
The date status only compares validity dates with the device clock. It does not verify signatures, establish chain trust, check hostname ownership or contact OCSP/CRL endpoints. Private keys, CSRs and PKCS#7 are not accepted.
Using the output
Copy a fingerprint or download PEM, DER or the JSON report.
Input up to 1 MiB; up to 20 PEM certificates or one DER file. Processing stops after 30 seconds.
Frequently asked questions
Which certificate formats are supported?
Paste one or more PEM certificates, or use Open PEM / DER for a certificate file. Select a certificate from the bundle to inspect its subject, issuer, serial number, public-key algorithm and signature algorithm.
Which fields and exports are available?
Review subject alternative names, CA constraints, key usages and raw extension OIDs. SHA-256 and SHA-1 fingerprints are calculated from the DER certificate bytes. Export the selected certificate as PEM or DER, or the bundle report as JSON.
Does decoding prove that a certificate is trusted?
The date status only compares validity dates with the device clock. It does not verify signatures, establish chain trust, check hostname ownership or contact OCSP/CRL endpoints. Private keys, CSRs and PKCS#7 are not accepted.
Is the input uploaded?
Processing stays in your browser. DevToolsy does not receive the pasted data or selected file.
Can I keep the result?
Copy a fingerprint or download PEM, DER or the JSON report.