KLklaussilveira·Jun 5, 2025Submission
Picohttpparser: Fast HTTP request/response parser in C
2 points · Open discussionh2o
picohttpparser
C2014–2025
h2o / picohttpparser
picohttpparser
tiny HTTP parser written in C (used in HTTP::Parser::XS et al.)
5Distinct people
5Mentions
0Explicit recommenders
2.1KGitHub stars
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What it is
tiny HTTP parser written in C (used in HTTP::Parser::XS et al.)
GitHub
Where it is used
No documented product use has been verified yet.
What people are saying
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This week on Hacker News
Nov 7–Nov 14 UTC · Direct repository links and separately labeled related project stories. Indexed through 11/14/2026, 3:56:07 PM UTC.
No direct repository links were found in the indexed HN discussions over the past seven days. Older discussions are available below.
Mentions over time
HN mentions by year5 dated mentions
Observed mentions: 2014-12-26 08:10:34 UTC to 2025-06-05 13:03:51 UTC.
Counts come from the repository’s dated source evidence. Index cutoff: 2026-11-02 08:16:59 UTC.
View mention counts and date ranges
| Period | Start (UTC) | End (exclusive, UTC) | Mentions | Submissions | Comments |
|---|---|---|---|---|---|
| 2014 | 2014-01-01 00:00:00 UTC | 2015-01-01 00:00:00 UTC | 1 | 0 | 1 |
| 2015 | 2015-01-01 00:00:00 UTC | 2016-01-01 00:00:00 UTC | 0 | 0 | 0 |
| 2016 | 2016-01-01 00:00:00 UTC | 2017-01-01 00:00:00 UTC | 0 | 0 | 0 |
| 2017 | 2017-01-01 00:00:00 UTC | 2018-01-01 00:00:00 UTC | 0 | 0 | 0 |
| 2018 | 2018-01-01 00:00:00 UTC | 2019-01-01 00:00:00 UTC | 0 | 0 | 0 |
| 2019 | 2019-01-01 00:00:00 UTC | 2020-01-01 00:00:00 UTC | 0 | 0 | 0 |
| 2020 | 2020-01-01 00:00:00 UTC | 2021-01-01 00:00:00 UTC | 0 | 0 | 0 |
| 2021 | 2021-01-01 00:00:00 UTC | 2022-01-01 00:00:00 UTC | 1 | 0 | 1 |
| 2022 | 2022-01-01 00:00:00 UTC | 2023-01-01 00:00:00 UTC | 2 | 0 | 2 |
| 2023 | 2023-01-01 00:00:00 UTC | 2024-01-01 00:00:00 UTC | 0 | 0 | 0 |
| 2024 | 2024-01-01 00:00:00 UTC | 2025-01-01 00:00:00 UTC | 0 | 0 | 0 |
| 2025 | 2025-01-01 00:00:00 UTC | 2026-01-01 00:00:00 UTC | 1 | 1 | 0 |
What Hacker News says
5 sourcesyou could try using https://libuv.org/ and https://github.com/h2o/picohttpparser
In Ask HN: Resources for Building a Webserver in C?Yea, it is definitely a fake HTTP server which I acknowledge in the article [1]. However based on the size of the requests, and my observation of the number of packets per second in/out being symmetrical at the network interface level, I didn't have a concern about doubled responses.
Skipping the parsing of the HTTP requests definitely gives a performance boost, but for this comparison both sides got the same boost, so I didn't mind being less strict. Seastar's HTTP parser was being finicky, so I chose the easy route and just removed it from the equation.
For reference though, in my previous post[2] libreactor was able to hit 1.2M req/s while fully parsing the HTTP requests using picohttpparser[3]. But that is still a very simple and highly optimized implementation. FYI, from what I recall, when I played with disabling HTTP parsing in lib
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reactor, I got a performance boost of about 5%.
1. https://talawah.io/blog/linux-kernel-vs-dpdk-http-performanc...
2. https://talawah.io/blog/extreme-http-performance-tuning-one-...
3. https://github.com/h2o/picohttpparser
The fact that someone wrote a parser that's hard to follow doesn't mean that parsing HTTP/1.x is extremely difficult. What is really hard is to construct a parser that is at the same time (1) fast, (2) complete, (3) secure. It is much easier to choose just two, compare e.g. the one based on Nginx[0] vs picohttpparser [1].
[0] https://github.com/Samsung/http-parser/blob/master/http_pars...
[1] https://github.com/h2o/picohttpparser/blob/master/picohttppa...
In Show HN: Micro HTTP server in 22 lines of CI'm skeptical of the performance numbers. First, like others here I don't believe nginx's performance will be a bottleneck for HTTP/2. Beyond that, I suspect there are cases in which this code is much worse than nginx.
Here's one. Look at the example request loop on <https://github.com/h2o/picohttpparser/>. It reads from a socket, appending to an initially-empty buffer. Then it tries to parse the buffer contents as an HTTP request. If the request is incomplete, the loop repeats. (h2o's lib/http1.c:handle_incoming_request appears to do the same thing.)
In particular, phr_parse_request doesn't retain any state between attempts. Each time, it goes through the whole buffer. In the degenerate case in which a client sends a large (n-byte) request one byte at a byte, it uses O(n^2) CPU for parsing. That extreme should be rare when clients are no
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t malicious, but the benchmark is probably testing the other extreme where all requests are in a single read. Typical conditions are probably somewhere between.