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Base64 is a binary-to-text encoding scheme that converts binary data into a set of 64 ASCII characters (A-Z, a-z, 0-9, +, /). It's widely used in email attachments (MIME), embedding images in HTML/CSS (Data URIs), storing complex data in JSON/XML, and API authentication (Basic Auth headers).
Base64 encoding takes 3 bytes (24 bits) of binary data and splits them into 4 groups of 6 bits each. Each 6-bit group maps to one of 64 characters. If the input isn't a multiple of 3 bytes, padding (=) is added. This means Base64 encoded data is approximately 33% larger than the original.
Standard Base64 uses + and / characters which have special meaning in URLs. URL-safe Base64 replaces + with - and / with _, making it safe for use in URL parameters and filenames without additional encoding.
No. Base64 is encoding, not encryption. It provides no security — anyone can decode Base64 text. Never use Base64 to protect sensitive data. Use proper encryption (like AES) instead.
Base64 converts 3 bytes into 4 characters, resulting in approximately 33% size increase. This is the trade-off for being able to represent binary data as safe ASCII text.
There's no theoretical limit, but browsers may struggle with very large strings (100MB+). For large files, consider streaming encoding or server-side processing.