`base64`

The Python base64 module provides functions for encoding binary data as printable ASCII characters and decoding those representations back to binary.

It implements the Base16, Base32, and Base64 encodings defined in RFC 4648, as well as the non-standard Base85 encoding. It’s useful when binary data must pass through text-based protocols, such as email, URLs, or HTTP.

Here’s a quick example:

>>> import base64

>>> encoded = base64.b64encode(b"hello, world")
>>> encoded
b'aGVsbG8sIHdvcmxk'

>>> base64.b64decode(encoded)
b'hello, world'

Key Features

Encodes and decodes Base64, Base32, Base16, and Base85 data
Provides URL-safe Base64 variants that replace + with - and / with _
Supports MIME-compliant encoding with newlines every 76 characters via encodebytes()
Accepts bytes-like objects and ASCII strings as inputs to decoding functions

Frequently Used Functions

Object	Type	Description
`base64.b64encode()`	Function	Encodes bytes using the standard Base64 alphabet
`base64.b64decode()`	Function	Decodes a Base64-encoded bytes-like object or ASCII string
`base64.urlsafe_b64encode()`	Function	Encodes using the URL- and filesystem-safe Base64 alphabet
`base64.urlsafe_b64decode()`	Function	Decodes URL-safe Base64 data
`base64.encodebytes()`	Function	Encodes bytes with MIME-compliant line breaks
`base64.b85encode()`	Function	Encodes bytes using the compact Base85 encoding

Examples

Encoding and decoding with the standard Base64 alphabet:

>>> import base64

>>> base64.b64encode(b"Python is great")
b'UHl0aG9uIGlzIGdyZWF0'
>>> base64.b64decode(b"UHl0aG9uIGlzIGdyZWF0")
b'Python is great'

Comparing the standard and URL-safe alphabets on bytes that produce + and /:

>>> base64.b64encode(b"\xff\xfe")
b'//4='
>>> base64.urlsafe_b64encode(b"\xff\xfe")
b'__4='

Common Use Cases

The most common tasks for base64 include:

Encoding binary files (images, PDFs) for embedding in JSON, XML, or HTML data URIs
Generating URL-safe tokens for password resets and API keys
Encoding email attachments in MIME format
Transmitting binary data over text-only channels or protocols

Real-World Example

Consider embedding a PNG image, logo.png, as a data URI for use directly in an HTML page:

import base64

with open("logo.png", "rb") as image_file:
    encoded = base64.b64encode(image_file.read()).decode("utf-8")

data_uri = f"data:image/png;base64,{encoded}"
html_snippet = f'<img src="{data_uri}" alt="Logo">'
print(html_snippet[:72] + "...")

When you run this script, you get an output like the following:

<img src="data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAYAAAA...

The .b64encode() call converts the raw bytes to a string the browser can read inline, eliminating the need for a separate image request.

Tutorial

Bytes Objects: Handling Binary Data in Python

In this tutorial, you'll learn about Python's bytes objects, which help you process low-level binary data. You'll explore how to create and manipulate byte sequences in Python and how to convert between bytes and strings. Additionally, you'll practice this knowledge by coding a few fun examples.

intermediate python

For additional information on related topics, take a look at the following resources: