JSON data in python is essentially a dictionary (at least they are interchangeable, there are some minor differences with the formatting). Have you tried saving a dictionary to a simple text file? my_data = { 'a': [1, 2, 3], 'b': {'foo': 'bar', 'baz': [4, 5, 6]} } with open('test_file.txt', 'w') as file: file.write(my_data) This is not possible because Python expects a string that it can write to a file. It doesn't know how to turn a dictionary into something it can write to a file. But, maybe you then do this instead: my_data = { "a": [1, 2, 3], "b": {"foo": "bar", "baz": [4, 5, 6]} } with open('test_file.txt', 'w') as file: # cast my_data to a string first file.write(str(my_data)) And it works. But what if you want to read that file? with open('test_file.txt', 'r') as file: read_data = file.read() Now you have a problem, because your output is this string: "{'a': [1, 2, 3], 'b': {'foo': 'bar', 'baz': [4, 5, 6]}}" How do you convert a string into a dictionary? This here doesn't work: with open('test_file.txt', 'r') as file: read_data = dict(file.read()) Python by itself does not know how to convert a string into a dictionary. For that you need JSON. Also it makes sure that you meet all the conventions of the JSON format so that you can exchange data between different languages (e.g. from Python to JavaScript). The other thing is, if you have a .txt file, how would anybody know that this file contains a data structure without opening the file? If the file extension says "JSON" everybody knows how to interpret the data. Same with .XML, .HTML etc. Answer from MattR0se on reddit.com