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-runtime >= "2.10.0"
  8. avro-compiler
  9. avro-simple
  10. aws-config
  11. aws-s3 < "4.5.1" | >= "4.8.0"
  12. awsm-codegen
  13. bap-radare2
  14. bitcoin >= "3.0"
  15. boulangerie
  16. builder-web >= "0.2.0"
  17. caisar
  18. calculon != "0.5"
  19. calculon-redis-lib
  20. calculon-web = "0.6"
  21. camelot >= "1.3.0"
  22. camels
  23. canary
  24. catala = "0.9.0" | >= "1.0.0~alpha"
  25. cb-check
  26. cbor >= "0.3"
  27. cconv-ppx
  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 >= "8.10.0+0.7.0" & < "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. docfd >= "2.1.0"
  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. gitlab
  78. goblint-cil >= "1.8.0"
  79. gopcaml-mode-merlin < "0.0.6"
  80. gradescope_submit
  81. graphql < "0.9.0" | >= "0.14.0"
  82. graphql-async >= "0.14.0"
  83. graphql-cohttp >= "0.13.0"
  84. graphql-lwt >= "0.14.0"
  85. graphql_ppx
  86. gremlin
  87. guardian
  88. h2
  89. hacl_x25519
  90. handlebars-ml
  91. hilite < "0.3.0"
  92. hl_yaml
  93. hockmd
  94. horned_worm
  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. jsonschema2atd
  113. jupyter
  114. jupyter-kernel
  115. jwto
  116. kappa-library < "4.1.3"
  117. karamel
  118. kaun >= "1.0.0~alpha1"
  119. kremlin < "transition"
  120. kubecaml
  121. lablgtk3-extras >= "3.0.1"
  122. lambdapi
  123. learn-ocaml
  124. letsencrypt
  125. letters
  126. libsail
  127. lichess_api
  128. linol >= "0.2" & < "0.10"
  129. linol-eio
  130. linol-lwt
  131. lockfree >= "0.3.1"
  132. logs-async-reporter >= "1.3"
  133. lsp < "1.6.0" | >= "1.23.1"
  134. melange-json = "1.2.0"
  135. melange-json-native
  136. merlin != "4.5-411"
  137. metadb
  138. mirage-crypto-ec
  139. mjson
  140. monorobot
  141. mopsa
  142. multicore-bench
  143. mutaml
  144. nloge
  145. nsq
  146. obuilder
  147. ocaml-lsp-server < "1.10.5" | >= "1.18.0" & != "1.21.0-4.14" & != "1.23.0"
  148. ocaml-protoc-plugin >= "6.1.0"
  149. ocaml_db_model
  150. ocaml_pgsql_model
  151. ocamleditor >= "1.15.2-ocaml414"
  152. ocf >= "1.0.0"
  153. ocsigen-start
  154. odoc >= "3.0.0"
  155. odoc-driver
  156. oframl
  157. oidc
  158. ojs-base
  159. ojs_base
  160. ometrics < "0.2.0"
  161. openai-gym
  162. openapi
  163. openapi_router
  164. opencage
  165. openstellina
  166. opium >= "0.19.0"
  167. oraft
  168. orun
  169. osh
  170. ozulip
  171. pa_ppx < "0.14" | >= "0.19"
  172. pandoc
  173. pbrt_yojson
  174. pds-reachability >= "0.2.3"
  175. petr4
  176. pgn_parser
  177. phylogenetics >= "0.2.0"
  178. piece_rope
  179. pkcs11-driver >= "1.0.0"
  180. ppx_deriving_jsonschema
  181. ppx_deriving_yojson < "3.6.1"
  182. ppx_protocol_conv_json < "5.0.0" | >= "5.2.1"
  183. ppx_yojson
  184. ppx_yojson_conv < "v0.13.0"
  185. ppx_yojson_conv_lib
  186. ppxlib-tools >= "0.37.0"
  187. prof_spacetime
  188. qmp >= "0.19.0"
  189. query-json
  190. quests
  191. r2pipe
  192. radare2
  193. rdf
  194. records = "0.6.0" | >= "1.0.0"
  195. repr-bench
  196. rfsm >= "2.2"
  197. rocq-devtools
  198. rpclib
  199. rungen
  200. rust-staticlib-gen
  201. SZXX
  202. safemoney
  203. saga
  204. sail < "0.15"
  205. saturn
  206. saturn_lockfree
  207. satyrographos != "0.0.2.7" & < "0.0.2.13"
  208. savvy
  209. semver2
  210. serde_json
  211. server-reason-react >= "0.4.0"
  212. sihl < "0.2.0" | >= "0.3.0~rc2"
  213. sihl-core
  214. slack
  215. slug
  216. smaws-lib
  217. smtml >= "0.7.0"
  218. snf_mcp < "0.2.1"
  219. spotify-web-api
  220. starred_ml
  221. swagger
  222. talon
  223. tdigest < "2.1.0"
  224. textmate-language >= "0.3.4"
  225. textrazor >= "0.1.1"
  226. tezos-context-hash-irmin
  227. tidy_email_sendgrid
  228. timedesc < "0.8.0"
  229. timedesc-json
  230. timere < "0.4.0"
  231. user-agent-parser
  232. vecosek
  233. vercel
  234. vscoq-language-server < "2.3.3"
  235. vsrocq-language-server
  236. wasm_of_ocaml-compiler
  237. webauthn
  238. why3find
  239. xapi-rrd >= "1.9.0"
  240. yojson-five >= "3.0.0"
  241. yosqlite >= "0.2"
  242. zanuda
  243. zarr

Conflicts

None