SAML Assertion Decoder — Base64 Decode and Lint XML SSO Payloads
Decode and inspect SAML 2.0 authentication assertions in your browser. Paste a Base64-encoded SAML Response or Assertion to view the NameID, attributes, conditions, issuer, and authentication context in a structured, readable layout. Free and private.
How to Use SAML Assertion Decoder — Base64 Decode and Lint XML SSO Payloads
How to Use the SAML Assertion Decoder:
Obtain the SAML Assertion: Capture the Base64-encoded SAML Response from your browser during an SSO login. In Chrome DevTools (Network tab), find the POST request to your Service Provider's Assertion Consumer Service (ACS) URL. The
SAMLResponseform field contains the Base64-encoded assertion.Paste and Decode: Paste the Base64 value into the input field and click "Decode Assertion". The tool supports standard Base64, Base64url (URL-safe), and URL-percent-encoded Base64.
Inspect the Subject (NameID): This is the unique identifier for the authenticated user — typically an email address or opaque persistent ID. The NameID Format tells you what kind of identifier it is.
Review Conditions: The validity window (NotBefore / NotOnOrAfter) tells you when the assertion is valid. The Audience restricts which Service Providers can accept it. An expired assertion will be highlighted in red.
Check Attributes: The Attribute Statement contains user attributes the Identity Provider (IdP) asserts about the user — such as email, name, roles, or department. Each attribute can have one or more values.
Authentication Context: The AuthnContextClassRef tells you how the user authenticated (e.g., PasswordProtectedTransport, MultiFactor).
Download XML: Expand the Raw XML section and click Download to save the decoded assertion as an .xml file for further inspection or troubleshooting.
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