Base64 Encode & Decode Online — Free Base64 Converter

Base64 is one of the most widely used encoding schemes in software development. It converts binary data into a string of printable ASCII characters, making it safe to transmit through text-based protocols that may not handle raw binary data correctly.

The name "Base64" comes from the 64-character alphabet used in the encoding: the uppercase letters A-Z (26), lowercase letters a-z (26), digits 0-9 (10), and two additional characters + and / (2). The = character is used for padding when the input length is not a multiple of 3.

How Base64 Encoding Works

The Base64 encoding process works in three steps:

1. Split input into 3-byte groups. Each group of 3 bytes (24 bits) is taken from the input data.
2. Divide into 4 groups of 6 bits. The 24 bits are split into four 6-bit values (each ranging from 0 to 63).
3. Map to the Base64 alphabet. Each 6-bit value is converted to its corresponding character in the Base64 alphabet (A=0, B=1, ..., Z=25, a=26, ..., z=51, 0=52, ..., 9=61, +=62, /=63).

If the input length is not a multiple of 3 bytes, padding characters (=) are added to make the output length a multiple of 4.

The Base64 Character Table

Encoding Example

Let's encode the string "Hi" step by step:

Common Use Cases for Base64

• Data URIs in HTML/CSS — Embed images, fonts, and other assets directly in HTML or CSS using data:image/png;base64,... syntax. This eliminates extra HTTP requests.
• HTTP Basic Authentication — The Authorization header uses Base64 to encode username:password as Basic dXNlcm5hbWU6cGFzc3dvcmQ=.
• Email Attachments (MIME) — Binary files attached to emails are Base64 encoded for safe transmission through SMTP, which is a text-based protocol.
• JSON Web Tokens (JWT) — JWTs encode their header and payload sections using Base64URL encoding (a URL-safe variant).
• Embedding binary in JSON/XML — Since JSON and XML are text formats, binary data (like images or certificates) must be Base64 encoded before embedding.
• API Payloads — Some APIs accept file uploads as Base64 encoded strings in the request body, avoiding multipart form data.

Base64 in Different Programming Languages

// Browser
btoa("Hello World")        // Encode: "SGVsbG8gV29ybGQ="
atob("SGVsbG8gV29ybGQ=")  // Decode: "Hello World"

// Node.js
Buffer.from("Hello World").toString("base64")
Buffer.from("SGVsbG8gV29ybGQ=", "base64").toString()

import base64
base64.b64encode(b"Hello World")  # b'SGVsbG8gV29ybGQ='
base64.b64decode(b"SGVsbG8gV29ybGQ=")  # b'Hello World'

import java.util.Base64;
Base64.getEncoder().encodeToString("Hello World".getBytes());
new String(Base64.getDecoder().decode("SGVsbG8gV29ybGQ="));

import "encoding/base64"
encoded := base64.StdEncoding.EncodeToString([]byte("Hello World"))
decoded, _ := base64.StdEncoding.DecodeString("SGVsbG8gV29ybGQ=")

Base64 vs Base64URL

Important: Base64 Is Not Encryption

A common misconception is that Base64 provides security. It does not. Base64 is a reversible encoding — anyone can decode a Base64 string without any secret key. Never use Base64 to "protect" passwords, API keys, or sensitive data. For actual security, use:

• Encryption — AES-256, RSA, or ChaCha20 for data confidentiality
• Hashing — SHA-256 or bcrypt for password storage
• TLS/HTTPS — For secure data transmission