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

Conflicts

None