Base64 Encode

When to encode to Base64

Base64 lets you put bytes where only text is allowed: data: URLs for small images, JSON fields that carry file contents, HTTP Basic authentication headers and e-mail attachments. Encoded data is about 33% larger than the original, so it is a transport format, not a storage format.

Choose the URL-safe alphabet in the ⋯ menu for tokens in URLs and file names. It replaces + and / with - and _ and drops the = padding, exactly as JSON Web Tokens do.

The tool works with any Unicode text: it converts text to UTF-8 bytes first, so accented letters and emoji survive the round trip. It runs entirely in your browser; nothing is sent to a server.

How Base64 works

The encoder takes three bytes (24 bits) at a time and splits them into four groups of six bits. Each group picks one of 64 characters: A–Z, a–z, 0–9, plus two symbols. The word Man becomes TWFu. When the input length is not a multiple of three, one or two = signs pad the final block.

The scheme is defined in RFC 4648, which also specifies Base32 and Base16. Older software follows RFC 2045 (MIME), whose decoders silently skip unexpected characters — convenient, but it can hide corrupted transfers. Choose the strict variant whenever both sides are under your control.

Encoding in code

• JavaScript: btoa() accepts only Latin-1, so convert first: btoa(String.fromCharCode(...new TextEncoder().encode(text))). In Node, use Buffer.from(text).toString('base64').
• Python: base64.b64encode(text.encode('utf-8')).decode(), or urlsafe_b64encode for the URL variant.
• Shell: printf %s 'text' | base64. Plain echo adds a newline that ends up encoded too.

Base64 is not encryption. Anyone can decode it, so never use it to hide passwords or keys.