JWT SUB Claim Explained
What is the JWT sub claim? Learn Subject meaning, examples, and validation rules for sub in JSON Web Tokens.
Quick Answer
To JWT SUB Claim Explained, paste your token into our JWT Decoder, inspect the header and payload claims, then verify the signature with the JWT Validator. All processing runs locally in your browser.
What Is the sub Claim?
The sub (Subject) claim identifies the principal (user or entity) that is the subject of the token.
Example
{ "sub": "user-123" }How to Inspect
Paste any JWT into JWT Decoder to see the sub claim in the decoded payload. Use JWT Debugger for validation warnings related to this claim.
Validation Rules
Must match the expected user ID. This is the primary identity claim.
Validating the Claim
Always verify JWT claims during token validation. Use our Claims Viewer and Debugger to inspect claim values in real tokens.
Browse related resources: JWT Decoder, JWT Validator, JWT Basics, JWT Authentication, JWT Errors, Algorithms, Glossary, and Learning Path.
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FAQ
What does this JWT claim mean?
See this page for a full explanation with JSON examples and validation rules for production APIs.
How do I view this claim in a token?
Paste your JWT into our free JWT Decoder or Claims Viewer to see all payload claims instantly.
Must I validate this claim server-side?
Registered claims like exp, iss, aud, and sub should always be validated during token verification.