A go (or 'golang' for search engine friendliness) implementation of JSON Web Tokens

2.0.0 is coming!

There are a couple open pull requests that contain breaking changes I believe are essential for moving this project forward. We will try to make upgrading as painless as possible (and the 1.x.x versions will remain available). If you believe this will effect you, please review the open pull requests and comment as soon as possible. I'm planning to land these changes Friday, Aug 22, 2014.

The changes are very small modifications to the API, but in keeping with the spirit of semantic versioning, I'm taking any breaking change seriously.

What the heck is a JWT?

In short, it's a signed JSON object that does something useful (for example, authentication). It's commonly used for Bearer tokens in Oauth 2. A token is made of three parts, separated by .'s. The first two parts are JSON objects, that have been base64url encoded. The last part is the signature, encoded the same way.

The first part is called the header. It contains the necessary information for verifying the last part, the signature. For example, which encryption method was used for signing and what key was used.

The part in the middle is the interesting bit. It's called the Claims and contains the actual stuff you care about. Refer to the RFC for information about reserved keys and the proper way to add your own.

What's in the box?

This library supports the parsing and verification as well as the generation and signing of JWTs. Current supported signing algorithms are RSA256 and HMAC SHA256, though hooks are present for adding your own.

Parse and Verify

Parsing and verifying tokens is pretty straight forward. You pass in the token and a function for looking up the key. This is done as a callback since you may need to parse the token to find out what signing method and key was used.

	token, err := jwt.Parse(myToken, func(token *jwt.Token) ([]byte, error) {
		return myLookupKey(token.Header["kid"])

	if err == nil && token.Valid {
	} else {

Create a token

	// Create the token
	token := jwt.New(jwt.GetSigningMethod("HS256"))
	// Set some claims
	token.Claims["foo"] = "bar"
	token.Claims["exp"] = time.Now().Add(time.Hour * 72).Unix()
	// Sign and get the complete encoded token as a string
	tokenString, err := token.SignedString(mySigningKey)

Project Status & Versioning

This library is considered production ready. Feedback and feature requests are appreciated. The API should be considered stable. There should be very few backwards-incompatible changes outside of major version updates (and only with good reason).

This project uses Semantic Versioning 2.0.0. Accepted pull requests will land on master. Periodically, versions will be tagged from master. You can find all the releases on the project releases page.


Documentation can be found on

The command line utility included in this project (cmd/jwt) provides a straightforward example of token creation and parsing as well as a useful tool for debugging your own integration. For a more http centric example, see this gist.

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    Package jwt is a Go implementation of JSON Web Tokens:

    See for more info.



    View Source
    const (
    	ValidationErrorMalformed        uint32 = 1 << iota // Token is malformed
    	ValidationErrorUnverifiable                        // Token could not be verified because of signing problems
    	ValidationErrorSignatureInvalid                    // Signature validation failed
    	ValidationErrorExpired                             // Exp validation failed
    	ValidationErrorNotValidYet                         // NBF validation failed

      The errors that might occur when parsing and validating a token


      View Source
      var TimeFunc = time.Now

        TimeFunc provides the current time when parsing token to validate "exp" claim (expiration time). You can override it to use another time value. This is useful for testing or if your server uses a different time zone than your tokens.


        func DecodeSegment

        func DecodeSegment(seg string) ([]byte, error)

          Decode JWT specific base64url encoding with padding stripped

          func EncodeSegment

          func EncodeSegment(seg []byte) string

            Encode JWT specific base64url encoding with padding stripped

            func RegisterSigningMethod

            func RegisterSigningMethod(alg string, f func() SigningMethod)

              Register the "alg" name and a factory function for signing method. This is typically done during init() in the method's implementation


              type Keyfunc

              type Keyfunc func(*Token) ([]byte, error)

                Parse methods use this callback function to supply the key for verification. The function receives the parsed, but unverified Token. This allows you to use propries in the Header of the token (such as `kid`) to identify which key to use.

                type SigningMethod

                type SigningMethod interface {
                	Verify(signingString, signature string, key []byte) error
                	Sign(signingString string, key []byte) (string, error)
                	Alg() string

                  Signing method

                  func GetSigningMethod

                  func GetSigningMethod(alg string) (method SigningMethod)

                    Get a signing method from an "alg" string

                    type SigningMethodHS256

                    type SigningMethodHS256 struct{}

                    func (*SigningMethodHS256) Alg

                    func (m *SigningMethodHS256) Alg() string

                    func (*SigningMethodHS256) Sign

                    func (m *SigningMethodHS256) Sign(signingString string, key []byte) (string, error)

                    func (*SigningMethodHS256) Verify

                    func (m *SigningMethodHS256) Verify(signingString, signature string, key []byte) (err error)

                    type SigningMethodRS256

                    type SigningMethodRS256 struct{}

                    func (*SigningMethodRS256) Alg

                    func (m *SigningMethodRS256) Alg() string

                    func (*SigningMethodRS256) Sign

                    func (m *SigningMethodRS256) Sign(signingString string, key []byte) (string, error)

                      Implements the Sign method from SigningMethod For this signing method, must be PEM encoded PKCS1 or PKCS8 RSA private key

                      func (*SigningMethodRS256) Verify

                      func (m *SigningMethodRS256) Verify(signingString, signature string, key []byte) error

                      type Token

                      type Token struct {
                      	Raw       string                 // The raw token.  Populated when you Parse a token
                      	Method    SigningMethod          // The signing method used or to be used
                      	Header    map[string]interface{} // The first segment of the token
                      	Claims    map[string]interface{} // The second segment of the token
                      	Signature string                 // The third segment of the token.  Populated when you Parse a token
                      	Valid     bool                   // Is the token valid?  Populated when you Parse/Verify a token

                        A JWT Token. Different fields will be used depending on whether you're creating or parsing/verifying a token.

                        func New

                        func New(method SigningMethod) *Token

                          Create a new Token. Takes a signing method

                          func Parse

                          func Parse(tokenString string, keyFunc Keyfunc) (*Token, error)

                            Parse, validate, and return a token. keyFunc will receive the parsed token and should return the key for validating. If everything is kosher, err will be nil

                            func ParseFromRequest

                            func ParseFromRequest(req *http.Request, keyFunc Keyfunc) (token *Token, err error)

                              Try to find the token in an http.Request. This method will call ParseMultipartForm if there's no token in the header. Currently, it looks in the Authorization header as well as looking for an 'access_token' request parameter in req.Form.

                              func (*Token) SignedString

                              func (t *Token) SignedString(key []byte) (string, error)

                                Get the complete, signed token

                                func (*Token) SigningString

                                func (t *Token) SigningString() (string, error)

                                  Generate the signing string. This is the most expensive part of the whole deal. Unless you need this for something special, just go straight for the SignedString.

                                  type ValidationError

                                  type ValidationError struct {
                                  	Errors uint32 // bitfield.  see ValidationError... constants
                                  	// contains filtered or unexported fields

                                    The error from Parse if token is not valid

                                    func (ValidationError) Error

                                    func (e ValidationError) Error() string

                                      Validation error is an error type


                                      Path Synopsis
                                      A useful example app.
                                      A useful example app.