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Upload the .cer file of your Certificado de Sello Digital (CSD) to confirm it is a CSD and not a FIEL, and to read the holder, RFC, serial number, and validity period the SAT assigned to it.

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Why telling a CSD from a FIEL matters

The SAT issues two kinds of certificate and they are not interchangeable. The FIEL (now called e.firma) identifies the taxpayer before the SAT: it is used for filings and to request the CSD itself. The CSD is the one that seals CFDI. Both arrive as .cer files that look identical, and mixing them up is one of the most common reasons credentials fail to load. The difference lives in the certificate’s keyUsage extension: This tool reads that extension and tells you which one you uploaded.
Everything runs in your browser. The certificate is read on your device using native browser APIs. Facturama receives no copy of your certificate and stores no data from it.
Do not upload your .key file or your password here. This tool only needs the .cer, which is the public half of the certificate. If what you need is converting the CSD to Base64 for the API, use the Base64 converter, which does need the key and also processes it in your browser.

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Known limits

Confirming that a .cer and a .key belong together requires decrypting the private key, and SAT keys ship as encrypted PKCS#8, often with 3DES. The browser’s cryptography API (Web Crypto) supports neither 3DES nor importing encrypted PKCS#8, so that check cannot be done client-side.If your credentials fail to load, upload the .cer here to rule out having mixed up the CSD with the FIEL, which is the most frequent cause.
The tool reads the certificate’s contents, but it does not confirm that the certification authority is really the SAT, nor does it check revocation lists. A self-signed certificate would be read without complaint.
If the certificate does not include keyUsage, there is no way to tell a CSD from a FIEL, and the tool says so explicitly instead of guessing. Certificates issued by the SAT always include it.

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Common errors

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Next steps

CFDI 4.0 XML validator

Verify that an invoice’s seal matches this certificate.

Test CSDs

Download the SAT test certificates to work in Sandbox.