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JWT Decoder

Decode and inspect JWT tokens instantly — header, payload, signature

Header 

                

              


              
              

                

                  Payload
                

                

                  

                

              


              
              

                

                  Signature
                

                

                  

                  
🔒 Signature verification requires the secret key — never share it client-side.

                

              

            


            
            
          

        

      


      
      
      

        
About JWT Decoder

        
JWT Decoder is a free, browser-based utility built for developers and engineers who need a fast, reliable way to decode and inspect jwt tokens instantly — header, payload, signature. Whether you're debugging an API response, preparing data for deployment, or validating configuration files, this tool handles the job in seconds — with zero server calls. Everything runs locally in your browser, so your source code and data stay private.

      


      
      

        
How to Use

        

          

            
1

            

              Paste your JWT token
              Copy the full JWT string (three Base64url segments separated by dots) and paste it into the input field.
            

          

          

            
2

            

              Click "Decode"
              The header and payload are instantly decoded and displayed as formatted JSON. Results appear immediately without any network request.
            

          

          

            
3

            

              Check expiry status
              If the payload contains an exp claim, a green or red banner shows whether the token is valid or expired.
            

          

          

            
4

            

              Inspect claims
              Review the payload for standard claims like sub, aud, iat, and any custom claims your application sets.
            

          

        

        

          ⚠️ Security note: The signature is not verified — verification requires the secret key, which should never be exposed client-side. This tool is safe for inspecting token structure and claims.
        

      


      
      
      

        
Frequently Asked Questions

        


          

            
            

              JSON Web Token (JWT) is an open standard (RFC 7519) for securely transmitting information between parties as a JSON object. The information is digitally signed so it can be verified and trusted. JWTs consist of three Base64url-encoded parts — Header, Payload, and Signature — joined by dots. They are widely used for authentication and authorisation in APIs and single-page applications.
            

          


          

            
            

              Yes — this tool runs entirely in your browser and makes no network requests. Your token is never sent to any server. However, as a general best practice, avoid pasting production tokens that contain sensitive personal data or long-lived credentials. Use short-lived tokens or sanitised examples when possible.
            

          


          

            
            

              Signature verification requires the secret key (for HMAC algorithms like HS256) or the private key (for asymmetric algorithms like RS256). These keys must be kept server-side. Exposing them in a client-side tool would completely defeat the security model of JWTs. You can verify the signature on your backend using your application's secret or public key.
            

          


          

            
            

              Header: Contains metadata about the token — typically the signing algorithm (alg, e.g. HS256) and token type (typ: "JWT").


              Payload: Contains the claims — statements about the user and additional data. Standard claims include sub (subject), exp (expiry), iat (issued at), and aud (audience).


              Signature: A cryptographic hash of the encoded header and payload, signed with the secret. This prevents tampering — if any part of the header or payload changes, the signature becomes invalid.
            

          

        

      


    


    
    

      
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Tool Info

        

          

            Category
            Developer
          

          

            Privacy
            
              🔒 Client-side
            
          

          

            Standard
            RFC 7519
          

          

            Verifies Sig.
            No (by design)
          

          

            Cost
            Free