Base64 Encoder / Decoder

Base64 encoding converts binary data into a 64-character ASCII subset (A–Z, a–z, 0–9, +, /), making it safe to transmit in systems designed for text, such as email (MIME), HTTP headers, and JSON payloads. The encoding increases data size by approximately 33% (every 3 bytes becomes 4 characters), which is an acceptable trade-off for compatibility. Base64 is not encryption — it is encoding. Anyone can decode a Base64 string instantly. It is used for transport compatibility, not security.

Practical use cases include: API authentication (HTTP Basic Auth encodes "username:password" as Base64 in the Authorization header), embedding small images in CSS or HTML as data URIs to eliminate HTTP requests, encoding binary attachments in email (MIME format), and passing binary data through systems that only accept text (some message queues, config files, environment variables). This tool supports both standard Base64 (RFC 4648) and URL-safe Base64 (replaces + with − and / with _, eliminating the need for percent-encoding in URLs). All encoding and decoding runs in the browser using the atob/btoa and TextEncoder APIs.