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Dollar Dhingra
Dollar Dhingra

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Benchmarking Python JSON serializers - json vs ujson vs orjson


If you work with a large datasets in json inside your python code, then you might want to try using 3rd party libraries like ujsonand orjson which are replacements to python’s json library.

As per their documentation

  • ujson (UltraJSON) is an ultra fast JSON encoder and decoder written in pure C with bindings for Python 3.7+.

  • orjson is a fast, correct JSON library for Python. It is the fastest python library for json encoding & decoding. It serializes dataclass, datetime, numpy, and UUID instances natively.


I did a basic benchmark comparing json, ujson and orjson. The benchmarking results were interesting.

import time
import json
import orjson
import ujson

def benchmark(name, dumps, loads):
    start = time.time()
    for i in range(3000000):
        result = dumps(m)
    print(name, time.time() - start)

if __name__ == " __main__":
    m = {
        "timestamp": 1556283673.1523004,
        "task_uuid": "0ed1a1c3-050c-4fb9-9426-a7e72d0acfc7",
        "task_level": [1, 2, 1],
        "action_status": "started",
        "action_type": "main",
        "key": "value",
        "another_key": 123,
        "and_another": ["a", "b"],

    benchmark("Python", json.dumps, json.loads)
    benchmark("ujson", ujson.dumps, ujson.loads)

    # orjson only outputs bytes, but often we need unicode:
    benchmark("orjson", lambda s: str(orjson.dumps(s), "utf-8"), orjson.loads)

# Python 12.502133846282959
# ujson 4.428200960159302
# orjson 2.3136467933654785

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ujson is 3 times faster than the standard json library

orjson is over 6 times faster than the standard json library


For most cases, you would want to go with python’s standard json library which removes dependencies on other libraries. On other hand you could try out ujsonwhich is simple replacement for python’s json library. If you want more speed and also want dataclass, datetime, numpy, and UUID instances and you are ready to deal with more complex code, then you can try your hands on orjson

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