Base64 Encoder & Decoder 100% Client-Side & Private
Encode plain text into Base64 or Base64URL and decode encoded strings instantly with multi-charset support (UTF-8, ASCII, UTF-16) and zero server exposure.
📘 The Complete Guide to Base64 & Base64URL Encoding
Replicating and improvising the capabilities of modern authentication toolkits like Authgear, this utility enables full control over binary-to-text representations for web tokens, headers, and protocol messages with zero latency and absolute privacy.
🔤 What is Base64 Encoding?
Base64 is a binary-to-text encoding scheme designed to safely transmit binary or arbitrary textual data over media designed for ASCII text. Every 3 raw bytes (24 bits) are split into 4 six-bit chunks, with each 6-bit chunk translated into one of 64 printable ASCII characters (A-Z, a-z, 0-9, +, and /).
🌐 Base64 vs. Base64URL
Standard Base64 contains characters + and / and trailing padding =, which have reserved syntactic meaning in URLs and query strings. Base64URL (RFC 4648 §5) replaces + with - and / with _, and strips padding to make tokens URL-safe for JSON Web Tokens (JWTs) and WebAuthn credentials.
🌍 Full UTF-8 & Emoji Support
Standard JavaScript btoa() and atob() functions only support 8-bit Latin-1 characters and throw errors when encountering Unicode code points or emojis. This engine implements proper multi-byte UTF-8, UTF-16LE, and UTF-16BE streams for seamless multilingual translation.
🔑 Common Developer Use Cases
Base64 is foundational in modern software engineering for constructing HTTP Authorization: Basic headers, decoding JWT claims and signatures, inspecting SAML responses, embedding small data URIs, and passing cryptographically signed tokens across microservices.
⚠️ Security Note: Encoding ≠ Encryption
Base64 is strictly a representation format and provides zero cryptographic confidentiality. Anyone can decode a Base64 string back into plain text instantly. Never use Base64 alone to protect sensitive passwords, keys, or personal identifiers.
🔒 100% Client-Side Privacy Guarantee
No text, authentication token, or configuration secret is ever uploaded to any external server or saved in third-party logs. All encoding and decoding operations execute strictly inside your browser's local sandbox memory.