# simdjson

12 Hacker News commenters recommended simdjson and 1 criticized it, November 2025 to November 2026. It was recommended in 7 of 13 months. It meets the Hacker Approved badge rule.

**Verdict:** Fast C++ JSON parser using SIMD, reaching gigabytes per second. Caveat: it still reads every byte, so there is no performance win when the whole input must be processed.

## Why people recommend it

- Parses gigabytes per second (2 comments): "You can parse JSON at several GB/s" ([source](https://news.ycombinator.com/item?id=46678625)) "can process gigabytes per second" ([source](https://news.ycombinator.com/item?id=47462245))
- Sparse access via ondemand API (2 comments): "take simdjson, use its ondemand api and then navigate it with .at_path(_with_wildcard)" ([source](https://news.ycombinator.com/item?id=47541317)) "It parses fast with SIMDJSON or doing various other approaches to parse sparsely." ([source](https://news.ycombinator.com/item?id=50137019))

## What people warn about

- No gain when whole input is read (2 comments): "But, if the application really needs to process every piece of the entire input, there's no performance win." ([source](https://news.ycombinator.com/item?id=49022701)) "Which is great, but a JSON parser fundamentally can't avoid looking at every byte." ([source](https://news.ycombinator.com/item?id=46513473))

## Alternatives hackers recommend

- [Jackson FasterXML](https://hackerapproved.com/p/jackson.md): 6 recommend
- [System.Text.Json](https://hackerapproved.com/p/system-text-json.md): 5 recommend

## Cite as

Hacker Approved, "simdjson", https://hackerapproved.com/p/simdjson/ (counts from 1,795,640 Hacker News comments, November 2025 to November 2026).