package yojson

  1. Overview
  2. Docs
Yojson is an optimized parsing and printing library for the JSON format

Install 

dune-project
 Dependency

github.com Readme Changelog BSD-3-Clause License Edit opam file Versions (15)

Authors

  1. M
    Martin Jambon

Maintainers

  1. P
    paul-elliot@tarides.com
  2. N
    nathan@tarides.com
  3. M
    marek@tarides.com

Sources

yojson-3.0.0.tbz
sha256=99414da7609b92a02474ef4b49ecda15edc8cbba5229341b124e7e4695c39610
sha512=896d0ea829a36ccadba6628800369c1a3ab9e7c64dbda8b76331889c9db481cd64e137f467481ae80a8dd5fca45d748bfa71f58641806cc1bb1a007f8291789f

Description

Yojson is an optimized parsing and printing library for the JSON format.

ydump is a pretty-printing command-line program provided with the yojson package.

Published: 02 Jun 2025

README

Yojson: JSON library for OCaml

Build Status

This library parses JSON data into a nested OCaml tree data structure.

Library documentation

Currently at https://ocaml-community.github.io/yojson/

Examples

A simple example on how to parse JSON from a string literal.

let json_string = {|
  {"number" : 42,
   "string" : "yes",
   "list": ["for", "sure", 42]}|}
(* val json_string : string *)

let json = Yojson.Safe.from_string json_string
(* val json : Yojson.Safe.t *)

let () = Format.printf "Parsed to %a" Yojson.Safe.pp json

Yojson is a pretty common choice for parsing JSON in OCaml, as such it is the base for a number of tools and libraries that are built on top of it.

  • ppx_deriving_yojson to automatically generate code that converts between Yojson.Safe.t and custom OCaml types
  • ppx_yojson_conv, an alternative to ppx_deriving_yojson from Jane Street with different design decisions
  • atd, generates mapping code from .atd specification files and can be used in multiple languages
  • jsonm is an alternate JSON parser that parses JSON into a stream of items, so the complete data structure does not have to be in memory.

Help wanted

Yojson is developed and maintained by volunteers — users like you. Various issues are in need of attention. If you'd like to contribute, please leave a comment on the issue you're interested in, or create a new issue. Experienced contributors will guide you as needed.

There are many simple ways of making a positive impact. For example, you can...

  • Use the software in your project.
  • Give a demo to your colleagues.
  • Share the passion on your blog.
  • Tweet about what you're doing with Yojson.
  • Report difficulties by creating new issues. We'll triage them.
  • Ask questions on StackOverflow.
  • Answer questions on StackOverflow.
  • Discuss usage on the OCaml forums.
  • Pick a task that's easy for you.

Check out in particular good first time issues and other issues with which we could use some help.

License

Yojson is licensed under the 3-clause BSD license, see LICENSE.md for details.

Dependencies (2)

  1. ocaml >= "4.08"
  2. dune >= "2.7"

Dev Dependencies (2)

  1. odoc with-doc
  2. alcotest with-test & >= "0.8.5"

  1. 0install >= "2.18"
  2. abella >= "2.0.8"
  3. acgtk
  4. anthropic
  5. archetype
  6. atd >= "2.6.0"
  7. atdgen >= "3.0.1"
  8. atdgen-runtime >= "2.10.0"
  9. atdml
  10. avro-compiler
  11. avro-simple
  12. aws-config
  13. aws-s3 < "4.5.1" | >= "4.8.0"
  14. awsm-codegen
  15. awso
  16. awso-common
  17. bap-radare2
  18. bitcoin >= "3.0"
  19. bizowie-api
  20. boulangerie
  21. builder-web >= "0.2.0"
  22. caisar
  23. calculon
  24. camelot >= "1.4.2"
  25. camels
  26. canary
  27. catala = "0.9.0" | >= "1.0.0~beta"
  28. cb-check
  29. cbor >= "0.3"
  30. chess_com_api
  31. colibrics
  32. comby-semantic
  33. commons
  34. containers >= "3.9"
  35. contract
  36. coq-lsp
  37. coq-of-ocaml
  38. coq-serapi < "8.20.0+0.20.0"
  39. crs >= "0.0.20250705"
  40. current_docker
  41. current_examples
  42. current_git
  43. current_github
  44. current_gitlab
  45. current_slack
  46. current_ssh
  47. current_web
  48. dap
  49. daypack-lib
  50. dblp-api
  51. decoders-yojson >= "0.7.0"
  52. devkit
  53. dnsrobot
  54. docker-api >= "0.2.2"
  55. docker_hub
  56. dot-merlin-reader < "4.9"
  57. dream
  58. dream-inertia
  59. dune-cargo-build
  60. dune-release >= "1.4.0"
  61. dune_deps_extra
  62. ecma-regex
  63. eio_main >= "0.10"
  64. elasticsearch-cli = "0.5"
  65. elpi >= "3.3.1"
  66. fehu < "1.0.0~alpha3"
  67. fiat-p256
  68. fit >= "1.2.0"
  69. forester >= "3.1.0"
  70. frama-c < "23.0" | >= "27.0~beta"
  71. fred
  72. frenetic
  73. fstar
  74. gapi-ocaml
  75. gdbprofiler
  76. gemini
  77. gendarme-json < "0.4.0"
  78. gendarme-yojson
  79. github != "4.0.0"
  80. github-data
  81. github-unix >= "4.5.1"
  82. gitlab
  83. goblint-cil >= "1.8.0"
  84. gopcaml-mode-merlin < "0.0.6"
  85. gradescope_submit
  86. graphql < "0.9.0" | >= "0.14.0"
  87. graphql-async >= "0.14.0"
  88. graphql-cohttp >= "0.13.0"
  89. graphql-lwt >= "0.14.0"
  90. graphql_ppx
  91. gremlin
  92. guardian
  93. h2
  94. hacl_x25519
  95. handlebars-ml
  96. hilite < "0.3.0"
  97. hl_yaml
  98. hockmd
  99. hpack
  100. hsluv
  101. httph
  102. huml
  103. huml-cli
  104. index-bench
  105. ip2location
  106. ip2locationio
  107. ip2whois
  108. irmin-graphql
  109. irmin-tezos
  110. jasmin
  111. jhupllib
  112. jose
  113. js_of_ocaml-compiler
  114. jsonrpc >= "1.23.1"
  115. jsonschema
  116. jsonschema-core
  117. jsonschema2atd
  118. jupyter
  119. jupyter-kernel
  120. jwto
  121. kappa-library < "4.1.3"
  122. karamel
  123. kaun >= "1.0.0~alpha1" & < "1.0.0~alpha3"
  124. kremlin < "transition"
  125. kubecaml
  126. lablgtk3-extras >= "3.0.1"
  127. lambdapi
  128. learn-ocaml
  129. letsencrypt < "2.0.0"
  130. letters
  131. libsail
  132. lichess_api
  133. linol >= "0.2" & < "0.10"
  134. linol-eio
  135. linol-lwt
  136. lockfree >= "0.3.1"
  137. logs-async-reporter >= "1.3"
  138. lsp < "1.6.0" | >= "1.23.1"
  139. melange-json = "1.2.0"
  140. melange-json-native
  141. merlin != "4.5-411"
  142. metadb
  143. miaou-core
  144. miaou-driver-web
  145. mirage-crypto-ec
  146. mjson
  147. monorobot
  148. mopsa
  149. multicore-bench
  150. mutaml
  151. nats-client
  152. nats-client-async
  153. neo4j_bolt
  154. nloge
  155. nsq
  156. obuilder
  157. ocaml-ai-sdk
  158. ocaml-lsp-server < "1.10.5" | >= "1.18.0" & != "1.21.0-4.14" & != "1.23.0"
  159. ocaml-protoc-plugin >= "6.1.0"
  160. ocaml_db_model
  161. ocaml_pgsql_model
  162. ocamleditor
  163. ocf >= "1.0.0"
  164. ochre
  165. ocsigen-start
  166. odoc >= "3.0.0"
  167. odoc-driver
  168. oframl
  169. oidc
  170. ojs-base
  171. ojs_base
  172. ometrics < "0.2.0"
  173. opam-check-npm-deps >= "4.1.0"
  174. openai-gym
  175. openapi
  176. openapi_router
  177. opencage
  178. openstellina
  179. opium >= "0.19.0"
  180. oraft
  181. orun
  182. osh
  183. oui
  184. ozulip
  185. pa_ppx < "0.14" | >= "0.19"
  186. pandoc
  187. pbrt_yojson
  188. pds-reachability >= "0.2.3"
  189. pgn_parser
  190. pgn_to_tex
  191. phylogenetics >= "0.2.0"
  192. piece_rope
  193. pkcs11-driver >= "1.0.0"
  194. polymarket
  195. ppx_deriving_jsonschema
  196. ppx_deriving_yojson < "3.6.1"
  197. ppx_protocol_conv_json >= "5.2.1"
  198. ppx_yojson
  199. ppx_yojson_conv_lib
  200. ppxlib-tools >= "0.37.0"
  201. prof_spacetime
  202. pxshot
  203. qdrant
  204. qmp >= "0.19.0"
  205. query-json
  206. quests
  207. r2pipe
  208. radare2
  209. rdf
  210. records >= "1.0.0"
  211. repr-bench
  212. rescriptdep
  213. rfsm >= "2.2"
  214. rocq-devtools
  215. rpclib
  216. rungen
  217. rust-staticlib-gen
  218. SZXX
  219. safemoney
  220. saga
  221. sail < "0.15"
  222. saturn
  223. saturn_lockfree
  224. satyrographos >= "0.0.2.8" & < "0.0.2.13"
  225. savvy
  226. semver2
  227. serde_json
  228. server-reason-react >= "0.4.0"
  229. shakuhachi
  230. sihl < "0.2.0" | >= "0.3.0~rc2"
  231. sihl-core
  232. simple_httpd
  233. slack
  234. slug
  235. smaws-lib
  236. smtml >= "0.7.0"
  237. snf_mcp < "0.2.1"
  238. spectrum_palette_ppx
  239. spotify-web-api
  240. starred_ml
  241. swagger
  242. talon < "1.0.0~alpha3"
  243. tdigest < "2.1.0"
  244. testcontainers
  245. textmate-language >= "0.3.4"
  246. textrazor >= "0.1.1"
  247. tidy_email_sendgrid
  248. timedesc < "0.8.0"
  249. timedesc-json
  250. timere < "0.4.0"
  251. transom
  252. user-agent-parser
  253. vecosek
  254. vercel
  255. volgo-vcs >= "0.0.22"
  256. vscoq-language-server < "2.3.3"
  257. vsrocq-language-server
  258. wasm_of_ocaml-compiler
  259. webauthn
  260. why3find
  261. xapi-rrd >= "1.9.0"
  262. yojson-five >= "3.0.0"
  263. yosqlite >= "0.2"
  264. yultracer
  265. zanuda
  266. zarr

Conflicts

None