Base64 Encode & Decode

Convert text to Base64 and back — emoji and accented characters included — or turn any file into a Base64 data URI. Everything happens in your browser.

How to encode or decode Base64

1. Choose Encode or Decode — or File → Base64 to convert a file.
2. Paste your text; the result updates as you type. Tick URL-safe for Base64URL output.
3. Copy the result, or press Swap to reverse the conversion.

How Base64 works

Base64 takes 3 bytes (24 bits) at a time and writes them as 4 characters from a 64-character alphabet: A–Z, a–z, 0–9, + and /. When the input isn't a multiple of 3 bytes, = padding fills the last group. The output is always about 33% larger than the input. It's an encoding for moving binary data through text-only channels — email, JSON, HTML — not encryption: anyone can decode it.

Base64 vs. Base64URL

Standard Base64 uses + and /, which have special meanings in URLs. The URL-safe variant (RFC 4648 §5) swaps them for - and _ and usually drops the = padding, so the value can sit in a URL, a file name or a JWT without escaping. The decoder above accepts both forms, with or without padding.

Why btoa() breaks on emoji

JavaScript's built-in btoa() only accepts characters up to U+00FF: emoji throw an InvalidCharacterError, and accented letters are encoded as Latin-1 instead of UTF-8, so other systems decode them wrongly. Convert to UTF-8 bytes first:

const b64 = btoa(String.fromCharCode(...new TextEncoder().encode(text)));
const text = new TextDecoder().decode(Uint8Array.from(atob(b64), (c) => c.charCodeAt(0)));

Related tools

• URL Encode & Decode
• JWT Decoder
• Hash Generator (MD5, SHA-256 & more)