JSON Web Token (JWT) Regex for Go

What this pattern does

This page provides a well-structured, multi-part regular expression for matching json web token (jwt), ported and verified for Go. A rigorously tested regex reduces debugging time and protects your application from edge-case failures. The snippet below is ready to drop into your Go project — whether you're validating in a Gin handler, a gRPC service, or a command-line tool.

Go Implementation

// JSON Web Token (JWT)
// ReDoS-safe | RegexVault — Web & Network > Misc

package validation

import "regexp"

var jsonWebTokenJwtRe = regexp.MustCompile(`^[A-Za-z0-9\-_]+\.[A-Za-z0-9\-_]+\.[A-Za-z0-9\-_]*$`)

func ValidateJsonWebTokenJwt(s string) bool {
    return jsonWebTokenJwtRe.MatchString(s)
}

// Example
// fmt.Println(ValidateJsonWebTokenJwt("eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJzdWIiOiIxMjM0NTY3ODkwIiwibmFtZSI6IkpvaG4gRG9lIiwiaWF0IjoxNTE2MjM5MDIyfQ.SflKxwRJSMeKKF2QT4fwpMeJf36POk6yJV_adQssw5c")) // true

Test Cases

When to use this pattern

This pattern is drawn from the Web & Network > Misc category and carries a ReDoS-safe certification. That matters for Go developers because Go's RE2 engine is inherently safe from catastrophic backtracking, but this pattern has been additionally verified for correctness. RegexVault audits patterns against known backtracking attack vectors, ensuring you have the necessary context before using this regex in a high-stakes production environment.

Common Pitfalls

Technical Notes

The signature section may be empty for unsigned tokens (alg: none). NEVER use alg: none in production — always validate algorithm. This regex validates structure only, not cryptographic validity.