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

Conflicts

None