Base64 Encode

How to Base64 encode text or a file

1. Text: type or paste it into the left box. The Base64 appears on the right as you type.
2. Image or file: press Encode a file… or drop the file anywhere on the tool. You get its MIME type, size, an image preview and a data URI.
3. Pick options if you need them: URL-safe (-_) for links, file names and tokens, No padding to drop the trailing =, and Wrap at 76 for email (MIME).
4. Press Copy, or Download to save the Base64 as a .txt file.

To turn Base64 back into text or a file, use the Base64 decoder, or press Swap ⇄ to decode the output right here.

Base64 encode examples

Text is converted to UTF-8 bytes first, which is what servers, browsers and programming languages expect. These results come from the encoder above:

How Base64 encoding works

Base64 (RFC 4648) writes any bytes using 64 characters that survive email, JSON, HTML and URLs: A–Z, a–z, 0–9, + and /. It takes the data 3 bytes (24 bits) at a time and splits them into four 6-bit numbers, each written as one character. The classic example is the word “Man”:

Regrouped into 6 bits: 010011 010110 000101 101110 = 19, 22, 5, 46 = TWFu. When the input isn't a multiple of 3 bytes, the last group is filled with zero bits and marked with =: “Ma” is TWE= and “M” is TQ==. That is why Base64 output is always about a third larger than the input.

Image to Base64 (data URI)

A data URI puts a whole file inside a URL: data:, the MIME type, ;base64, and the Base64. Browsers treat it like a link to the file, so you can use it in HTML, CSS, Markdown, JSON or email templates without hosting the image. This is a real 1 × 1 pixel PNG (68 bytes):

<img src="data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAQAAAC1HAwCAAAAC0lEQVR42mNkYAAAAAYAAjCB0C8AAAAASUVORK5CYII=" alt="">

The encoder can give you the plain data URI, the Base64 on its own, a ready <img> tag or a CSS background-image: url(…). Data URIs can't be cached separately and are a third larger than the file, so keep them for small images:

URL-safe Base64 and padding

Standard Base64 uses + and /, which mean “space” and “path separator” in URLs, and =, which separates query parameters. URL-safe Base64 (base64url, RFC 4648 §5) swaps them for - and _ and usually drops the padding. You can see the difference in the last row of the table above: Pz8/Pj4+ becomes Pz8_Pj4-. JSON Web Tokens are three base64url strings joined by dots; the JWT decoder reads them. If you must put standard Base64 in a URL, percent-encode it with the URL encoder instead.

Base64 encode in JavaScript, Python and the command line

JavaScript: btoa() only accepts characters up to U+00FF. It throws on emoji, and it encodes “é” as the Latin-1 byte (6Q==) instead of UTF-8 (w6k=). Convert to UTF-8 first:

const bytes = new TextEncoder().encode("café 😀");
const b64 = btoa(Array.from(bytes, (b) => String.fromCharCode(b)).join(""));
// Node.js: Buffer.from("café 😀").toString("base64")   ("base64url" for URL-safe)

Python:

import base64
base64.b64encode("café".encode("utf-8")).decode()        # 'Y2Fmw6k='
base64.urlsafe_b64encode(data).rstrip(b"=")              # URL-safe, no padding

Linux and macOS: printf '%s' 'Hello, World!' | base64 gives SGVsbG8sIFdvcmxkIQ==. Using echo adds a newline and gives SGVsbG8sIFdvcmxkIQo=. For a file: base64 -w 0 image.png on Linux (no line wrapping) or base64 -i image.png on macOS. Windows PowerShell: [Convert]::ToBase64String([IO.File]::ReadAllBytes("image.png")).

Related developer tools

• Base64 decoder: Base64 back to text, or to an image, PDF or file.
• URL encoder: percent-encode text for query strings and links.
• JWT decoder: read the base64url parts of a JSON Web Token.

Frequently asked questions