How to Encode Text to Base64

Encode text to Base64 in JavaScript (browser)

The built-in btoa() function encodes strings in the browser, but only handles Latin-1. Use TextEncoder for full UTF-8 support:

// Simple Latin-1 encode (built-in)
const encoded = btoa("Hello, World!");
// → "SGVsbG8sIFdvcmxkIQ=="

// UTF-8 safe encode (handles emoji and non-ASCII)
function encodeBase64(str) {
  const bytes = new TextEncoder().encode(str);
  const binStr = Array.from(bytes, b => String.fromCharCode(b)).join('');
  return btoa(binStr);
}
encodeBase64("Hello 😀"); // → "SGVsbG8g8J+YgA=="

Encode text to Base64 in Node.js

Node.js Buffer handles Base64 encoding natively without any imports:

// Encode a UTF-8 string to Base64
const text = "Hello, World!";
const encoded = Buffer.from(text, "utf8").toString("base64");
console.log(encoded); // → "SGVsbG8sIFdvcmxkIQ=="

// Encode a binary file to Base64
const fs = require("fs");
const fileData = fs.readFileSync("./image.png");
const base64 = fileData.toString("base64");

Encode text to Base64 in Python

Python's standard library includes Base64 encoding in the base64 module:

import base64

# Encode a UTF-8 string to Base64
text = "Hello, World!"
encoded = base64.b64encode(text.encode("utf-8")).decode("utf-8")
print(encoded)  # → SGVsbG8sIFdvcmxkIQ==

# URL-safe Base64 (uses - and _ instead of + and /)
url_safe = base64.urlsafe_b64encode(text.encode("utf-8")).decode("utf-8")

Encode to Base64 in the terminal (macOS/Linux)

Use the built-in base64 command to encode strings or files from the command line:

# Encode a string (note: echo adds a newline — use printf for clean output)
printf 'Hello, World!' | base64
# → SGVsbG8sIFdvcmxkIQ==

# Encode a file to Base64
base64 < image.png > image.b64

HTTP Basic Authentication

HTTP Basic Auth requires credentials formatted as username:password encoded in Base64 inside the Authorization header.

const credentials = btoa("username:password");
fetch("/api/data", {
  headers: { "Authorization": `Basic ${credentials}` }
});

Embedding images in HTML / CSS

Inline small images directly in your markup using a Base64 data URI, saving an HTTP round-trip.

<!-- HTML -->
<img src="data:image/png;base64,iVBORw0KGgo..." alt="icon" />

/* CSS */
.logo { background-image: url("data:image/svg+xml;base64,PHN2..."); }

Passing binary data through JSON APIs

JSON doesn't support raw binary. Encode binary blobs (images, PDFs, files) to Base64 before including them in JSON payloads.

const payload = {
  filename: "report.pdf",
  content: Buffer.from(pdfBytes).toString("base64"),
  mimeType: "application/pdf"
};
await fetch("/api/upload", {
  method: "POST",
  body: JSON.stringify(payload)
});

Storing secrets in environment variables

Binary keys and certificates can't be stored directly in .env files. Encode them to Base64 first.

# Encode a binary key file
base64 < private-key.pem > key.b64

# In your .env file
PRIVATE_KEY_BASE64="LS0tLS1CRUdJTiBQUklWQVRFIEtFWS0tLS0t..."

# Decode at runtime (Node.js)
const key = Buffer.from(process.env.PRIVATE_KEY_BASE64, "base64").toString();