❕ Benchmarks regenerated on 2026-07-13
This repository contains benchmarks for Python JSON readers & writers. What's the fastest Python JSON parser? Let's find out.
To run the tests yourself:
git clone git@github.com:TkTech/json_benchmark.git && cd json_benchmark
<setup a virtualenv using your tool of choice>
poetry install
pytest --benchmark-json benchmark.json --benchmark-histogram histograms/To update the tables in the README.md with the new results, just run:
python generate_benchmark_summaries.py
python generate_minefield_reports.py
The following libraries are the current candidates for benchmarking. Feel free to request or add new libraries.
| Library | Reader | Writer | Streaming | Version |
|---|---|---|---|---|
| simdjson | Yes | No | No | 7.0.3 |
| cysimdjson | Yes | No | No | 23.9 |
| yyjson | Yes | Yes | Yes | 5.0.0 |
| orjson | Yes | Yes | No | 3.11.9 |
| rapidjson | Yes | Yes | No | 1.23 |
| ujson | Yes | Yes | No | 5.13.0 |
| json | Yes | Yes | No | 3.11 |
| msgspec | Yes | Yes | No | 0.21.1 |
| ijson | Yes | No | Yes | 3.5.1 |
"Streaming" indicates a SAX-style / incremental parser that dispatches JSON tokens without building the whole document in memory. These are compared separately in the "Streaming parse of ..." benchmark groups.
cd It doesn't matter how fast a JSON parser is if it's not going to give you the correct results. We run the JSON minefield against each library. To see the complete line-by-line results, see the <minefield_reports/> directory.
See full minefield results for yyjson.
| count | result |
|---|---|
| 283 | 🎉 expected result |
| 0 | 🔥 parsing should have failed but succeeded |
| 0 | 🔥 parsing should have succeeded but failed |
| 6 | ➕ result undefined, parsing succeeded |
| 29 | ➖ result undefined, parsing failed |
See full minefield results for yyjson-sax.
| count | result |
|---|---|
| 283 | 🎉 expected result |
| 0 | 🔥 parsing should have failed but succeeded |
| 0 | 🔥 parsing should have succeeded but failed |
| 6 | ➕ result undefined, parsing succeeded |
| 29 | ➖ result undefined, parsing failed |
See full minefield results for rapidjson.
| count | result |
|---|---|
| 277 | 🎉 expected result |
| 6 | 🔥 parsing should have failed but succeeded |
| 0 | 🔥 parsing should have succeeded but failed |
| 6 | ➕ result undefined, parsing succeeded |
| 29 | ➖ result undefined, parsing failed |
See full minefield results for orjson.
| count | result |
|---|---|
| 283 | 🎉 expected result |
| 0 | 🔥 parsing should have failed but succeeded |
| 0 | 🔥 parsing should have succeeded but failed |
| 6 | ➕ result undefined, parsing succeeded |
| 29 | ➖ result undefined, parsing failed |
See full minefield results for simdjson.
| count | result |
|---|---|
| 283 | 🎉 expected result |
| 0 | 🔥 parsing should have failed but succeeded |
| 0 | 🔥 parsing should have succeeded but failed |
| 4 | ➕ result undefined, parsing succeeded |
| 31 | ➖ result undefined, parsing failed |
See full minefield results for ujson.
| count | result |
|---|---|
| 267 | 🎉 expected result |
| 16 | 🔥 parsing should have failed but succeeded |
| 0 | 🔥 parsing should have succeeded but failed |
| 21 | ➕ result undefined, parsing succeeded |
| 14 | ➖ result undefined, parsing failed |
See full minefield results for msgspec.
| count | result |
|---|---|
| 283 | 🎉 expected result |
| 0 | 🔥 parsing should have failed but succeeded |
| 0 | 🔥 parsing should have succeeded but failed |
| 6 | ➕ result undefined, parsing succeeded |
| 29 | ➖ result undefined, parsing failed |
See full minefield results for ijson.
| count | result |
|---|---|
| 282 | 🎉 expected result |
| 1 | 🔥 parsing should have failed but succeeded |
| 0 | 🔥 parsing should have succeeded but failed |
| 16 | ➕ result undefined, parsing succeeded |
| 19 | ➖ result undefined, parsing failed |
In these benchmarks, lower is better.
Sample file is 2251051 bytes.
| library | min (ms) | max (ms) | mean (ms) |
|---|---|---|---|
| yyjson | 8.6970 | 9.3007 | 8.8893 |
| ijson (yajl2_c) | 22.6858 | 23.8652 | 23.1013 |
Sample file is 1727204 bytes.
| library | min (ms) | max (ms) | mean (ms) |
|---|---|---|---|
| yyjson | 3.3277 | 4.8824 | 3.7323 |
| ijson (yajl2_c) | 6.3018 | 8.5975 | 6.9487 |
Sample file is 631514 bytes.
| library | min (ms) | max (ms) | mean (ms) |
|---|---|---|---|
| yyjson | 1.7940 | 2.0859 | 1.8278 |
| ijson (yajl2_c) | 2.8267 | 5.3436 | 2.9626 |
Sample file is 7 bytes.
| library | min (ms) | max (ms) | mean (ms) |
|---|---|---|---|
| yyjson | 0.0011 | 0.0212 | 0.0012 |
| ijson (yajl2_c) | 0.0037 | 0.1267 | 0.0039 |
Sample file is 48765043 bytes.
| library | min (ms) | max (ms) | mean (ms) |
|---|---|---|---|
| yyjson | 315.4146 | 319.3040 | 317.5809 |
| ijson (yajl2_c) | 495.1035 | 505.1622 | 499.9637 |
Sample file is 66409302 bytes.
| library | min (ms) | max (ms) | mean (ms) |
|---|---|---|---|
| yyjson | 646.0111 | 659.2554 | 651.9847 |
| ijson (yajl2_c) | 1020.1002 | 1032.1442 | 1027.0863 |
Sample file is 3512883 bytes.
| library | min (ms) | max (ms) | mean (ms) |
|---|---|---|---|
| yyjson | 7.6482 | 11.5492 | 7.8543 |
| ijson (yajl2_c) | 9.3670 | 9.6594 | 9.5128 |
Sample file is 3327831 bytes.
| library | min (ms) | max (ms) | mean (ms) |
|---|---|---|---|
| yyjson | 4.7380 | 5.4931 | 4.8932 |
| ijson (yajl2_c) | 5.1025 | 5.9048 | 5.2717 |
Sample file is 2251051 bytes.
| library | min (ms) | max (ms) | mean (ms) |
|---|---|---|---|
| yyjson | 4.4991 | 6.7486 | 4.8984 |
| orjson | 6.0146 | 20.8946 | 12.1758 |
| msgspec | 6.6082 | 27.9779 | 15.5113 |
| simdjson | 7.2701 | 20.6712 | 14.5211 |
| ujson | 11.1293 | 25.2489 | 18.3757 |
| json | 23.8417 | 34.6569 | 28.9730 |
| rapidjson | 24.6718 | 39.5648 | 32.8370 |
Sample file is 1727030 bytes.
| library | min (ms) | max (ms) | mean (ms) |
|---|---|---|---|
| yyjson | 1.7838 | 3.2357 | 1.9707 |
| orjson | 2.4194 | 13.5199 | 4.6141 |
| msgspec | 3.0889 | 21.4627 | 6.3947 |
| simdjson | 3.3927 | 16.4161 | 6.1467 |
| ujson | 4.4742 | 19.0578 | 7.3929 |
| rapidjson | 4.5165 | 21.7992 | 7.4734 |
| json | 6.2320 | 14.9818 | 7.9924 |
Sample file is 567916 bytes.
| library | min (ms) | max (ms) | mean (ms) |
|---|---|---|---|
| orjson | 0.8095 | 13.5349 | 1.1043 |
| yyjson | 0.8694 | 1.5064 | 0.9441 |
| msgspec | 1.0577 | 17.2088 | 1.4776 |
| simdjson | 1.3933 | 14.9575 | 1.7529 |
| ujson | 1.6982 | 14.8908 | 2.1086 |
| rapidjson | 1.8627 | 15.8346 | 2.2719 |
| json | 2.6851 | 13.7934 | 2.9656 |
Sample file is 7 bytes.
| library | min (ms) | max (ms) | mean (ms) |
|---|---|---|---|
| msgspec | 0.0001 | 0.0039 | 0.0001 |
| yyjson | 0.0001 | 0.0025 | 0.0001 |
| orjson | 0.0001 | 0.0017 | 0.0001 |
| rapidjson | 0.0003 | 0.0017 | 0.0003 |
| ujson | 0.0003 | 0.0043 | 0.0003 |
| simdjson | 0.0004 | 0.0098 | 0.0004 |
| json | 0.0008 | 0.0049 | 0.0008 |
Sample file is 45690911 bytes.
| library | min (ms) | max (ms) | mean (ms) |
|---|---|---|---|
| yyjson | 226.2088 | 239.0445 | 230.9776 |
| orjson | 470.7608 | 544.2078 | 507.9765 |
| msgspec | 474.9090 | 539.3030 | 508.0502 |
| rapidjson | 607.6599 | 671.6313 | 642.6487 |
| json | 658.0721 | 700.5949 | 674.1365 |
| ujson | 795.8875 | 926.3975 | 873.1998 |
| simdjson | 852.5420 | 919.4318 | 881.5412 |
Sample file is 66409251 bytes.
| library | min (ms) | max (ms) | mean (ms) |
|---|---|---|---|
| yyjson | 559.2589 | 575.5079 | 570.1669 |
| msgspec | 1051.5780 | 1180.5235 | 1115.4705 |
| orjson | 1105.1228 | 1175.1532 | 1142.0121 |
| ujson | 1286.0061 | 1469.6067 | 1364.5810 |
| rapidjson | 1296.9691 | 1427.1810 | 1359.3918 |
| simdjson | 1357.0520 | 1529.2694 | 1430.5631 |
| json | 1572.2035 | 1680.6050 | 1615.5561 |
Sample file is 1707203 bytes.
| library | min (ms) | max (ms) | mean (ms) |
|---|---|---|---|
| orjson | 4.4288 | 5.2035 | 4.5914 |
| yyjson | 4.6131 | 5.3194 | 4.7907 |
| msgspec | 4.7112 | 6.7624 | 5.3332 |
| simdjson | 5.2242 | 6.5857 | 5.4582 |
| ujson | 5.7027 | 8.0437 | 6.4811 |
| json | 6.3685 | 9.7802 | 7.2586 |
| rapidjson | 7.4218 | 8.2376 | 7.6006 |
Sample file is 3327831 bytes.
| library | min (ms) | max (ms) | mean (ms) |
|---|---|---|---|
| msgspec | 2.5023 | 14.6973 | 3.0122 |
| yyjson | 2.5452 | 3.1216 | 2.6679 |
| simdjson | 2.8363 | 17.3013 | 3.2583 |
| orjson | 3.5744 | 14.2182 | 3.7913 |
| rapidjson | 4.3007 | 17.6994 | 4.7676 |
| json | 4.4708 | 16.9558 | 5.2436 |
| ujson | 4.6627 | 22.6703 | 5.6661 |
| library | min (ms) | max (ms) | mean (ms) |
|---|---|---|---|
| json_merge_patch | 0.0005 | 0.0803 | 0.0007 |
| yyjson | 0.0010 | 0.0277 | 0.0011 |
Generally, unless you control the CI runners with self-hosted boxes (which are unsafe on public Github projects!), you have no idea what machine you're going to get, or how many other jobs may be running on the same machine. This can cause the benchmarks to vary drastically between runs, even minutes apart. For this reason benchmarks are always run locally on a consistent machine, in a consistent state.
x64 tests are run on an AMD Ryzen 7 5800X, capped at base clock speed with 64GB of Corsair CMW32GX4M2E3200C16.
This repository isn't for arguing the pros or cons of JSON versus some other exchange format. You frequently have no choice but to work with JSON, and if you can read or write responses 15% faster, that means you can handle more requests per second with the same hardware.
