Validate JWT token in Ruby

This is a memo when verifying the AWS Cognito web token.

[JSON Web Token Verification -Amazon Cognito]( html)

Cognito allows you to download a JWK set for verification for each user pool


Gem to use

jwt jwt/ruby-jwt: A ruby implementation of the RFC 7519 OAuth JSON Web Token (JWT) standard.

Used to decode regular JWT tokens


nov/json-jwt: JSON Web Token and its family (JSON Web Signature, JSON Web Encryption and JSON Web Key) in Ruby

Used to create a public key from a public JSON web key (JWK)


#Download JWK set
uri = ""
response = Net::HTTP.get_response(URI.parse(uri))
jwks = JSON.parse(response.body)

#Decode JWT without verification
token = JWT.decode(jwt, nil, false)

#Get the kid match from the JWK set
jwk = jwks["keys"].find { |obj| obj["kid"] == token[1]["kid"] }

#Create public key
public_key =

#Exception when decoding verification using public key is invalid
JSON::JWT.decode(jwt, public_key)

If you find it helpful, please LGTM

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