How To Decode And Encode In Base64 In Python 3

Python3 Base64 binary file open

Are you working with an application that needs to transmit and store the binary data over to a network that can only handle only textual form of data? Well then encoding your binary data to Base64 is your solution because this scheme can be used to format data into a string of ASCII characters.

Base64 encoding scheme is important because it makes sure that the data doesn’t get modified during the process of transferring or storage. Base64 tells us that we can represent 64 different characters and numbers using this base system that means at least 6 bits are required to represent a single character.

In this article we shall look at the process of how we can encode or decode strings, images, urls and binary data into Base64 using Python and explore the libraries that are involved in the process.

Encoding Strings using Base64

In python3 we have a module called base64 which allows us to encode data. To import the module we use the following syntax:

import base64

In this module we have a function called b64encode() which helps perform base64 encoding. This function takes a bytes object  as a parameter and returns a Base64 bytes object. The format of using b64encode() is :


The variable should always be a bytes like object but what if we need to encode a string to Base64. To encode strings in Base64 the process is first converting the string using encode() method into bytes and then using b64encode() method. Let’s look at an example of converting string to base64:

import base64

str_example = "Python is the best programming language"
str_to_bytes = str_example.encode("ascii") #we have an encoded string
bytes_to_base64= base64.b64encode(str_to_bytes)#encoding bytes to base64
#returns decoded string of base64
base64_output = bytes_to_base64.decode('ascii')


Since we know that b64encode returns a byte-like object which is shown in the first print statement. To convert it to a string we can use the decode() method with the parameter we want to decode it into. To prevent any data loss or corruption the main thing to remember is that the encoding and decoding format should always be the same.

Encoding URL/FileNames to Base64

Base64 provides another method to ensure safe URL encoding which can also be used for naming files. As we know that the characters like “\”, “<”, ”>”, “{“ and ”}” are the unsafe characters for naming files or using in a url. The method used for encoding urls is:


This method converts the “+” and “/” sign to “-” and “_” respectively. Let’s understand this with an example:

import base64

str_url = "abc9+"

url_bytes = str_url.encode("utf-8")
#URL to base64 encoding
url_base64 = base64.urlsafe_b64encode(url_bytes)
#base64 to url
base64_str = url_base64.decode('utf-8')


Encoding Image in Base64

Using the base64 module we can also encode an image. You can download a sample image from google and use it. We will first open the file in “rb” mode instead of “r” which is necessary because this opens the file in binary format. Let’s look at the code for encoding an image in Base64 using python.

import base64

#open file in binary read mode
with open("flower.jpg", "rb") as image:
   encoded_image = base64.b64encode(



The output may be different according to the image chosen. Please note this can also be used for text or pdf files.

Encoding binary data to Base64

The b64encode() method takes binary as an input so we have one step less to do while encoding binary data to Base64. Let’s take a look at an example of encoding binary data to base64.

import base64

binary_data = b'\x00\xFF\x00\xFF\x00\xFF'
data_base64 = base64.b64encode(binary_data)
base64_string = data_base64.decode('utf-8')



Encoding JSON in Base64

JSON API is the designated way used for exchanging data between websites, mobile applications or servers. Python3 has a builtin module “json” that helps us to convert python objects into JSON. If in any case you want to encode the json object to a base64 encoded string, there is no straightforward way to do that, First you have to convert the JSON object into string by using the json.dumps method and then finally encode that string into base64. Let’s look at it through an example.

import json
import base64

dict_data = {"language": "Python"}
json_data = json.dumps(dict_data)
json_b64 = base64.b64encode(json_data.encode('utf-8'))


Before encoding the data to base64 converting it into bytes is necessary that’s why data is passed into encode function first and converted into the utf-8 format and then the resulting bytes object is passed to the base64.

Encoding Zip Files into Base64

Python3 is extremely flexible in encoding and decoding of data. It’s possible to encode zip files using the b64encode method. We can use the same methods to encode and decode zip files as used earlier only difference is that we need to use python’s open method to read the zip file in binary mode and then after converting it to base64 using the same method we have to re-write the converted output into the new file so let’s take a look on how we can do it.

import base64

with open('', 'rb') as file_input, open('', 'w') as file_output:


The output is an encoded base64 zip file.

File needs to be read in binary mode as the encode method accepts binary data as input. Please note that multiple context support is only available in Python 3.x. This code is efficient since it doesn’t store data read in memory.

Decoding Base64 to string

Decoding is basically the reverse of what happens in encoding. The base64 string is decoded into bytes which is then converted to strings. The decode method is available in the “base64” module. The method used for decoding is as follows :


Let’s now take a look at a real example using the b64decode method. The string we shall use shall be the output encoded string of the first example.

import base64
#encoded string from first example
b64_str = "UHl0aG9uIGlzIHRoZSBiZXN0IHByb2dyYW1taW5nIGxhbmd1YWdl"
b64_str = b64_str.encode('ascii')
b64_bytes = base64.b64decode(b64_str)
decode_str = b64_bytes.decode('ascii')


As you can see in the output the string was correctly decoded. Please note that method “b64decode” takes a bytes like object as input.

Base64 URL FileNames Decoding and using UTF-8

The method “urlsafe_b64decode()” is similar to the default decoding method in the base64 module. The difference is that it uses this character “_” instead of “/” and “-” character instead of “=”. The method syntax is as follows:


The urlsafe method takes an encoded base64 string as parameter and returns a byte object. Now let’s implement this using an example.

import base64

b64_str = "aGVsbG8gd29ybGQ="
url_bytes_b64 = base64.urlsafe_b64decode(b64_str)
str_64 = str(url_bytes_b64, "utf-8")


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