Base64 Encode and Decode

Type or paste into either field and the other updates as you type. Text is encoded as UTF-8, so English and other Latin-script text, Cyrillic, every other Unicode script and emoji survive a round trip. Decoding ignores whitespace and line breaks, accepts missing = padding and strips a pasted data:...;base64, prefix.

URL-safe uses the - and _ alphabet of RFC 4648 section 5. Line breaks every 76 chars wraps output like MIME email. To encode a file, press File → data URL or drop it onto the Base64 field. You get a data:<mime>;base64,... string; the data URL prefix checkbox, shown while a file is loaded, switches to bare Base64. Text files also fill the Text field.

Example

Text field: tool bit is fun

dG9vbCBiaXQgaXMgZnVu

The 15 bytes split into five groups of 3, so there is no = padding. Other scripts work the same way: Greek Ελληνικά gives zpXOu867zrfOvc65zrrOrA==, Chinese 你好 gives 5L2g5aW9.

Base64 in code

const bytes = new TextEncoder().encode("tool bit is fun");
const b64 = btoa(String.fromCharCode(...bytes));
// dG9vbCBiaXQgaXMgZnVu

const text = new TextDecoder().decode(
  Uint8Array.from(atob(b64), (c) => c.charCodeAt(0)),
);

import base64

b64 = base64.b64encode("tool bit is fun".encode("utf-8")).decode("ascii")
text = base64.b64decode(b64).decode("utf-8")

printf 'tool bit is fun' | base64              # dG9vbCBiaXQgaXMgZnVu
printf 'dG9vbCBiaXQgaXMgZnVu' | base64 -d      # tool bit is fun

Limitations

• Text (as UTF-8), decoded output and files are limited to 1 MB (1,000,000 bytes). Above that the tool shows an error and does not convert.
• Line breaks are \n, not MIME’s CRLF, with no trailing newline.
• URL-safe output keeps = padding.
• Base64 alphabets are strict: - or _ in standard mode, or + or / in URL-safe mode, gives an error with a hint to switch.
• Data URLs always use the standard alphabet without line breaks; URL-safe and Line breaks affect only bare Base64.
• Decoding is UTF-8 only. Invalid bytes show as � with a note; there is no other charset and no hex view.

FAQ