Base64 Encoder/Decoder

How to Use the Base64 Encoder/Decoder

1. To Encode: Select the Encode tab, type or paste your text, and click "Encode to Base64". The Base64-encoded result appears in the output area.
2. To Decode: Select the Decode tab, paste your Base64 string, and click "Decode from Base64". The original text appears in the output area.
3. Click Copy to copy the result to your clipboard.
4. This tool handles UTF-8 characters including emojis, accented letters, and non-Latin scripts.

About Base64 Encoding

Base64 is a group of binary-to-text encoding schemes that represent binary data in an ASCII string format. It uses a set of 64 characters (A-Z, a-z, 0-9, +, /) to represent binary data, with = used as padding. Base64 encoding is widely used in web development, email systems (MIME), and data storage where binary data needs to be stored or transferred as text.

Common use cases include embedding images in CSS or HTML using data URIs, encoding file attachments in emails, storing binary data in JSON or XML, and transmitting data through URLs. While Base64 increases the data size by approximately 33%, it guarantees safe transport through systems that only handle text. Note that Base64 is an encoding scheme, not encryption, and should never be used for security purposes.

Common Base64 Use Cases

Base64 encoding appears throughout web development and software engineering. Here are the most frequent scenarios where you will encounter or need Base64.

Data URIs for Inline Images

Embed small images directly in HTML or CSS to avoid extra HTTP requests:

<img src="data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAEAAAAB
CAYAAAAC1HAwCAAAAC0lEQVQI12NgAAIABQABNjN9GQAAAAlwSFlzAAAWJQ
AAFiUBSVIk8AAAABl0RVh0..." alt="pixel">

Basic Authentication Header

HTTP Basic Auth encodes credentials as Base64:

username:password  =>  dXNlcm5hbWU6cGFzc3dvcmQ=

Authorization: Basic dXNlcm5hbWU6cGFzc3dvcmQ=

JSON Web Tokens (JWT)

JWTs use Base64URL encoding for the header and payload sections:

Header:  {"alg":"HS256","typ":"JWT"}
Base64:  eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9

Payload: {"sub":"1234567890","name":"John"}
Base64:  eyJzdWIiOiIxMjM0NTY3ODkwIiwibmFtZSI6IkpvaG4ifQ

Email Attachments (MIME)

Content-Type: application/pdf; name="report.pdf"
Content-Transfer-Encoding: base64

JVBERi0xLjQKMSAwIG9iago8PAovVHlwZSAvQ2F0YWxvZwov...

Storing Binary Data in JSON

{
  "filename": "photo.jpg",
  "content_type": "image/jpeg",
  "data": "iVBORw0KGgoAAAANSUhEUgAA..."
}

Base64 Quick Reference

The Base64 alphabet consists of 64 characters plus a padding character. Understanding the encoding table helps when debugging or manually inspecting encoded data.

Size Overhead Comparison

Technical Background: How Base64 Works

Base64 encoding works by taking groups of three bytes (24 bits) from the input and splitting them into four groups of 6 bits each. Each 6-bit group maps to one of 64 characters in the Base64 alphabet (A-Z, a-z, 0-9, +, /). Because 6 bits can represent values 0-63, this creates a one-to-one mapping from bit patterns to printable ASCII characters. When the input length is not a multiple of three bytes, padding with one or two = characters is added to make the output a multiple of four characters.

This encoding scheme was designed to solve a fundamental problem in computing: many data transport systems were built to handle text, not binary data. Email protocols, JSON, XML, HTML, and many database systems can corrupt binary data by interpreting control characters, stripping high bits, or performing character set conversions. By converting binary data to a limited set of universally safe ASCII characters, Base64 guarantees that the data survives transport intact.

The trade-off is a 33% increase in size, since every 3 bytes become 4 characters. For small payloads like authentication tokens, cryptographic keys, or small icons, this overhead is negligible. For large files, the overhead can be significant, which is why file uploads typically use multipart form encoding rather than Base64. The Base64URL variant (replacing + with - and / with _) was created because standard Base64 characters have special meaning in URLs and file systems.

Frequently Asked Questions