OAuth 2.0 Refresh Token (Generic) Regex for Go

What this pattern does

This page provides a lightweight, single-purpose regular expression for matching oauth 2.0 refresh token (generic), ported and verified for Go. In security-sensitive code, using an unverified regex can open the door to both false positives and denial-of-service attacks. 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

// OAuth 2.0 Refresh Token (Generic)
// ReDoS-safe | RegexVault — Security > OAuth & OIDC

package validation

import "regexp"

var oauth20RefreshTokenGenericRe = regexp.MustCompile(`^[A-Za-z0-9\-_.+/=]{40,512}$`)

func ValidateOauth20RefreshTokenGeneric(s string) bool {
    return oauth20RefreshTokenGenericRe.MatchString(s)
}

// Example
// fmt.Println(ValidateOauth20RefreshTokenGeneric("1//0gBcDeFgHiJkLmNoPqRsTuVwXyZ01234567890aBcDeFgHiJkLmNoPqR")) // true

Test Cases

When to use this pattern

This pattern is drawn from the Security > OAuth & OIDC 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

Refresh tokens are long-lived (hours to years) credentials used to obtain new access tokens. They must be stored securely (not in localStorage or cookies without Secure/HttpOnly flags). Rotation on use (refresh token rotation) is best practice.