Base64 Tool

What Is Base64 Encoding?

Base64 is an encoding scheme that converts binary data into ASCII text using 64 printable characters. This encoding allows binary data to be transmitted through systems designed for text, such as email, JSON, XML, and URLs.

URL-Safe Base64

Standard Base64 uses + and / characters, which have special meanings in URLs. URL-safe Base64 replaces these characters with - and _, making the encoded data safe to use in URLs without escaping. URL-safe Base64 is essential for JWT tokens, which are often passed in URLs or headers where standard Base64 characters would cause problems.

Our tool includes a URL-safe toggle that automatically converts between standard and URL-safe Base64 formats. When encoding for use in URLs, query parameters, or JWT tokens, always enable the URL-safe option.

Understanding JWT (JSON Web Tokens)

JWT (JSON Web Token) is a compact, URL-safe token format used for authentication and information exchange. A JWT consists of three parts separated by dots: header.payload.signature. Each part is Base64 encoded (URL-safe), making JWTs easy to transmit in URLs, cookies, and HTTP headers.

JWT Structure:

• Header: Contains token type (JWT) and signing algorithm (HS256, RS256, etc.)
• Payload: Contains claims (user data, permissions, expiration time)
• Signature: Cryptographic signature ensuring the token hasn't been tampered with

Our JWT decoder automatically splits the token and decodes each part, displaying the JSON contents of the header and payload. This helps developers debug authentication issues, inspect token claims, check expiration times, and verify token structure.

JWT Security Considerations

JWTs are encoded, not encrypted—anyone can decode and read the contents. Never store sensitive information (passwords, secrets) in JWT payloads. The signature prevents tampering but doesn't hide the data. JWTs should be transmitted over HTTPS and stored securely. Check the exp (expiration) claim to ensure tokens are still valid.

PEM Certificate Parsing

PEM (Privacy Enhanced Mail) is a text format for storing certificates and keys. PEM files contain Base64-encoded certificate data wrapped in -----BEGIN CERTIFICATE----- and -----END CERTIFICATE----- markers. Our tool decodes PEM certificates and extracts important information like common name (CN), issuer, expiration date, and validity period.

System administrators use PEM certificate parsing to quickly verify certificate details without opening the certificate in external tools. This is particularly useful when troubleshooting SSL/TLS issues, verifying certificate chains, checking expiration dates, or confirming that certificates match their intended domains.

Certificate Fields Explained

• Common Name (CN): The domain name the certificate is issued for
• Organization (O): The company or entity the certificate belongs to
• Issuer: The Certificate Authority (CA) that signed the certificate
• Valid From/To: The certificate's validity period—certificates expire and must be renewed
• Serial Number: Unique identifier for this certificate
• Subject Alternative Names (SAN): Additional domains covered by this certificate

Frequently Asked Questions

Can I decode Base64 without this tool?

Yes—any programming language with Base64 support can decode it. JavaScript: atob(base64string). Command line: echo "base64string" | base64 -d. Python: base64.b64decode(). This web tool provides a convenient interface without writing code.

How do I verify a JWT token is valid?

Decoding a JWT only reads its contents—it doesn't verify the signature. To fully validate a JWT, you need the signing secret (for HMAC) or public key (for RSA) and must verify the signature matches. Our tool decodes the token for inspection but doesn't perform signature verification. Check the exp claim to see if the token has expired.