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. avro-compiler
  10. avro-simple
  11. aws-config
  12. aws-s3 < "4.5.1" | >= "4.8.0"
  13. awsm-codegen
  14. bap-radare2
  15. bitcoin >= "3.0"
  16. boulangerie
  17. builder-web >= "0.2.0"
  18. caisar
  19. calculon != "0.5"
  20. calculon-redis-lib
  21. calculon-web = "0.6"
  22. camelot >= "1.3.0"
  23. camels
  24. canary
  25. catala = "0.9.0" | >= "1.0.0~beta"
  26. cb-check
  27. cbor >= "0.3"
  28. cconv-ppx
  29. chess_com_api
  30. colibrics
  31. comby-semantic
  32. commons
  33. containers >= "3.9"
  34. coq-lsp
  35. coq-of-ocaml
  36. coq-serapi >= "8.10.0+0.7.0" & < "8.20.0+0.20.0"
  37. crs >= "0.0.20250705"
  38. current_docker
  39. current_examples
  40. current_git
  41. current_github
  42. current_gitlab
  43. current_slack
  44. current_ssh
  45. current_web
  46. dap
  47. daypack-lib
  48. dblp-api
  49. decoders-yojson >= "0.7.0"
  50. devkit
  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
  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. horned_worm
  96. hpack
  97. hsluv
  98. httph
  99. huml
  100. huml-cli
  101. index-bench
  102. ip2location
  103. ip2locationio
  104. ip2whois
  105. irmin-graphql
  106. irmin-tezos
  107. jasmin
  108. jhupllib
  109. jose
  110. js_of_ocaml-compiler
  111. jsonrpc >= "1.23.1"
  112. jsonschema
  113. jsonschema2atd
  114. jupyter
  115. jupyter-kernel
  116. jwto
  117. kappa-library < "4.1.3"
  118. karamel
  119. kaun >= "1.0.0~alpha1"
  120. kremlin < "transition"
  121. kubecaml
  122. lablgtk3-extras >= "3.0.1"
  123. lambdapi
  124. learn-ocaml
  125. letsencrypt
  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. mirage-crypto-ec
  140. mjson
  141. monorobot
  142. mopsa
  143. multicore-bench
  144. mutaml
  145. neo4j_bolt
  146. nloge
  147. nsq
  148. obuilder
  149. ocaml-lsp-server < "1.10.5" | >= "1.18.0" & != "1.21.0-4.14" & != "1.23.0"
  150. ocaml-protoc-plugin >= "6.1.0"
  151. ocaml_db_model
  152. ocaml_pgsql_model
  153. ocamleditor >= "1.15.2-ocaml414"
  154. ocf >= "1.0.0"
  155. ocsigen-start
  156. odoc >= "3.0.0"
  157. odoc-driver
  158. oframl
  159. oidc
  160. ojs-base
  161. ojs_base
  162. ometrics < "0.2.0"
  163. opam-check-npm-deps >= "4.1.0"
  164. openai-gym
  165. openapi
  166. openapi_router
  167. opencage
  168. openstellina
  169. opium >= "0.19.0"
  170. oraft
  171. orun
  172. osh
  173. ozulip
  174. pa_ppx < "0.14" | >= "0.19"
  175. pandoc
  176. pbrt_yojson
  177. pds-reachability >= "0.2.3"
  178. petr4
  179. pgn_parser
  180. phylogenetics >= "0.2.0"
  181. piece_rope
  182. pkcs11-driver >= "1.0.0"
  183. polymarket
  184. ppx_deriving_jsonschema
  185. ppx_deriving_yojson < "3.6.1"
  186. ppx_protocol_conv_json < "5.0.0" | >= "5.2.1"
  187. ppx_yojson
  188. ppx_yojson_conv < "v0.13.0"
  189. ppx_yojson_conv_lib
  190. ppxlib-tools >= "0.37.0"
  191. prof_spacetime
  192. pxshot
  193. qdrant
  194. qmp >= "0.19.0"
  195. query-json
  196. quests
  197. r2pipe
  198. radare2
  199. rdf
  200. records = "0.6.0" | >= "1.0.0"
  201. repr-bench
  202. rfsm >= "2.2"
  203. rocq-devtools
  204. rpclib
  205. rungen
  206. rust-staticlib-gen
  207. SZXX
  208. safemoney
  209. saga
  210. sail < "0.15"
  211. saturn
  212. saturn_lockfree
  213. satyrographos != "0.0.2.7" & < "0.0.2.13"
  214. savvy
  215. semver2
  216. serde_json
  217. server-reason-react >= "0.4.0"
  218. shakuhachi
  219. sihl < "0.2.0" | >= "0.3.0~rc2"
  220. sihl-core
  221. simple_httpd
  222. slack
  223. slug
  224. smaws-lib
  225. smtml >= "0.7.0"
  226. snf_mcp < "0.2.1"
  227. spotify-web-api
  228. starred_ml
  229. swagger
  230. talon
  231. tdigest < "2.1.0"
  232. testcontainers
  233. textmate-language >= "0.3.4"
  234. textrazor >= "0.1.1"
  235. tidy_email_sendgrid
  236. timedesc < "0.8.0"
  237. timedesc-json
  238. timere < "0.4.0"
  239. user-agent-parser
  240. vecosek
  241. vercel
  242. volgo-vcs >= "0.0.22"
  243. vscoq-language-server < "2.3.3"
  244. vsrocq-language-server
  245. wasm_of_ocaml-compiler
  246. webauthn
  247. why3find
  248. xapi-rrd >= "1.9.0"
  249. yojson-five >= "3.0.0"
  250. yosqlite >= "0.2"
  251. zanuda
  252. zarr

Conflicts

None