Base64 Encoder & Decoder — Free Online Tool

What Is Base64 Encoding?

Base64 is a binary-to-text encoding scheme that converts binary data into a string of 64 printable ASCII characters. It is defined in RFC 4648 and is used whenever binary data needs to travel through text-only channels — like email (MIME), JSON APIs, HTML data URIs, or HTTP headers.

The encoding alphabet consists of A–Z, a–z, 0–9, +, and / (plus = for padding). The URL-safe variant (Base64URL) replaces + with - and / with _ to avoid conflicts in URLs and filenames.

Base64 is not encryption. It is a reversible encoding that anyone can decode. Never use Base64 to protect sensitive data like passwords or API keys.

How Base64 Encoding Works

Base64 converts every 3 bytes (24 bits) of input into 4 characters (6 bits each) from the Base64 alphabet. Here is the classic example — encoding the word "Man":

Result: "Man" → "TWFu"

Base64 Alphabet Table

The standard Base64 character set maps values 0–63 to these 64 characters:

URL-safe variant: value 62 maps to - (instead of +) and value 63 maps to _ (instead of /). Padding = is omitted. Use this when embedding Base64 in URLs, filenames, or JWT tokens.

Common Uses of Base64

Base64 encoding appears everywhere in modern web development:

Base64 Encoding vs Encryption

A common misconception is that Base64 provides security. It does not:

How to Encode & Decode Base64 in Code

Quick reference for Base64 encoding in the most popular languages:

JavaScript

// Encode
const encoded = btoa("Hello, World!");
// "SGVsbG8sIFdvcmxkIQ=="

// Decode
const decoded = atob("SGVsbG8sIFdvcmxkIQ==");
// "Hello, World!"

// Unicode-safe encode (handles emojis, CJK, etc.)
const utf8 = new TextEncoder().encode("Hello");
const b64 = btoa(String.fromCharCode(...utf8));

Python

import base64

# Encode
encoded = base64.b64encode(b"Hello, World!").decode()
# "SGVsbG8sIFdvcmxkIQ=="

# Decode
decoded = base64.b64decode("SGVsbG8sIFdvcmxkIQ==").decode()
# "Hello, World!"

# URL-safe
url_safe = base64.urlsafe_b64encode(b"data").decode()

Command Line (Linux / macOS)

# Encode
echo -n "Hello, World!" | base64
# SGVsbG8sIFdvcmxkIQ==

# Decode
echo "SGVsbG8sIFdvcmxkIQ==" | base64 --decode
# Hello, World!

# Encode a file
base64 image.png > image.b64

Frequently Asked Questions