Base64 Encode & Decode Online

Base64 is a binary-to-text encoding scheme that represents binary data using 64 printable ASCII characters (A-Z, a-z, 0-9, +, /). It is commonly used to safely transmit binary data over text-based systems like email (MIME), JSON APIs, and HTTP headers.

No. Base64 is a reversible encoding, not encryption. Anyone can decode a Base64 string without needing a key. Never use Base64 to protect sensitive data like passwords or API keys — use proper encryption instead.

Standard Base64 uses + and / characters, which have special meaning in URLs. URL-safe Base64 (RFC 4648 Section 5) replaces + with - and / with _. It is used in JWT tokens, OAuth tokens, URL query parameters, and filenames.

The = character is padding. Base64 processes input in groups of 3 bytes. If the input length is not a multiple of 3, the output is padded: 1 byte remaining adds ==, 2 bytes remaining adds =. This ensures the output length is always a multiple of 4.

The most likely cause is the wrong character set. Try UTF-8 first — it handles almost everything modern. If the source is a legacy Windows or regional system, try ISO-8859-1 or the matching variant. If the Base64 represents binary data (images, PDFs), it will not render as readable text.

Yes. Everything runs entirely inside your browser using client-side JavaScript. No text or string is ever uploaded to any server. This makes it safe for encoding API keys, authentication tokens, or confidential data.

Yes. After the first page load all assets are cached, so the Base64 encoder/decoder works offline in any modern browser.