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. boulangerie
  18. builder-web >= "0.2.0"
  19. caisar
  20. calculon != "0.5"
  21. calculon-redis-lib
  22. calculon-web = "0.6"
  23. camelot >= "1.3.0"
  24. camels
  25. canary
  26. catala = "0.9.0" | >= "1.0.0~beta"
  27. cb-check
  28. cbor >= "0.3"
  29. cconv-ppx
  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 >= "8.10.0+0.7.0" & < "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. eio_main >= "0.10"
  62. elasticsearch-cli = "0.5"
  63. elpi >= "3.3.1"
  64. fehu < "1.0.0~alpha3"
  65. fiat-p256
  66. fit >= "1.2.0"
  67. forester >= "3.1.0"
  68. frama-c < "23.0" | >= "27.0~beta"
  69. fred
  70. frenetic
  71. fstar
  72. gapi-ocaml
  73. gdbprofiler
  74. gemini
  75. gendarme-json < "0.4.0"
  76. gendarme-yojson
  77. github != "4.0.0"
  78. github-data
  79. github-unix >= "4.5.1"
  80. gitlab
  81. goblint-cil >= "1.8.0"
  82. gopcaml-mode-merlin < "0.0.6"
  83. gradescope_submit
  84. graphql < "0.9.0" | >= "0.14.0"
  85. graphql-async >= "0.14.0"
  86. graphql-cohttp >= "0.13.0"
  87. graphql-lwt >= "0.14.0"
  88. graphql_ppx
  89. gremlin
  90. guardian
  91. h2
  92. hacl_x25519
  93. handlebars-ml
  94. hilite < "0.3.0"
  95. hl_yaml
  96. hockmd
  97. horned_worm
  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. jsonschema2atd
  116. jupyter
  117. jupyter-kernel
  118. jwto
  119. kappa-library < "4.1.3"
  120. karamel
  121. kaun >= "1.0.0~alpha1" & < "1.0.0~alpha3"
  122. kremlin < "transition"
  123. kubecaml
  124. lablgtk3-extras >= "3.0.1"
  125. lambdapi
  126. learn-ocaml
  127. letsencrypt < "2.0.0"
  128. letters
  129. libsail
  130. lichess_api
  131. linol >= "0.2" & < "0.10"
  132. linol-eio
  133. linol-lwt
  134. lockfree >= "0.3.1"
  135. logs-async-reporter >= "1.3"
  136. lsp < "1.6.0" | >= "1.23.1"
  137. melange-json = "1.2.0"
  138. melange-json-native
  139. merlin != "4.5-411"
  140. metadb
  141. mirage-crypto-ec
  142. mjson
  143. monorobot
  144. mopsa
  145. multicore-bench
  146. mutaml
  147. neo4j_bolt
  148. nloge
  149. nsq
  150. obuilder
  151. ocaml-lsp-server < "1.10.5" | >= "1.18.0" & != "1.21.0-4.14" & != "1.23.0"
  152. ocaml-protoc-plugin >= "6.1.0"
  153. ocaml_db_model
  154. ocaml_pgsql_model
  155. ocamleditor >= "1.15.2-ocaml414"
  156. ocf >= "1.0.0"
  157. ocsigen-start
  158. odoc >= "3.0.0"
  159. odoc-driver
  160. oframl
  161. oidc
  162. ojs-base
  163. ojs_base
  164. ometrics < "0.2.0"
  165. opam-check-npm-deps >= "4.1.0"
  166. openai-gym
  167. openapi
  168. openapi_router
  169. opencage
  170. openstellina
  171. opium >= "0.19.0"
  172. oraft
  173. orun
  174. osh
  175. oui
  176. ozulip
  177. pa_ppx < "0.14" | >= "0.19"
  178. pandoc
  179. pbrt_yojson
  180. pds-reachability >= "0.2.3"
  181. petr4
  182. pgn_parser
  183. phylogenetics >= "0.2.0"
  184. piece_rope
  185. pkcs11-driver >= "1.0.0"
  186. polymarket
  187. ppx_deriving_jsonschema
  188. ppx_deriving_yojson < "3.6.1"
  189. ppx_protocol_conv_json < "5.0.0" | >= "5.2.1"
  190. ppx_yojson
  191. ppx_yojson_conv < "v0.13.0"
  192. ppx_yojson_conv_lib
  193. ppxlib-tools >= "0.37.0"
  194. prof_spacetime
  195. pxshot
  196. qdrant
  197. qmp >= "0.19.0"
  198. query-json
  199. quests
  200. r2pipe
  201. radare2
  202. rdf
  203. records = "0.6.0" | >= "1.0.0"
  204. repr-bench
  205. rfsm >= "2.2"
  206. rocq-devtools
  207. rpclib
  208. rungen
  209. rust-staticlib-gen
  210. SZXX
  211. safemoney
  212. saga
  213. sail < "0.15"
  214. saturn
  215. saturn_lockfree
  216. satyrographos != "0.0.2.7" & < "0.0.2.13"
  217. savvy
  218. semver2
  219. serde_json
  220. server-reason-react >= "0.4.0"
  221. shakuhachi
  222. sihl < "0.2.0" | >= "0.3.0~rc2"
  223. sihl-core
  224. simple_httpd
  225. slack
  226. slug
  227. smaws-lib
  228. smtml >= "0.7.0"
  229. snf_mcp < "0.2.1"
  230. spectrum_palette_ppx
  231. spotify-web-api
  232. starred_ml
  233. swagger
  234. talon < "1.0.0~alpha3"
  235. tdigest < "2.1.0"
  236. testcontainers
  237. textmate-language >= "0.3.4"
  238. textrazor >= "0.1.1"
  239. tidy_email_sendgrid
  240. timedesc < "0.8.0"
  241. timedesc-json
  242. timere < "0.4.0"
  243. user-agent-parser
  244. vecosek
  245. vercel
  246. volgo-vcs >= "0.0.22"
  247. vscoq-language-server < "2.3.3"
  248. vsrocq-language-server
  249. wasm_of_ocaml-compiler
  250. webauthn
  251. why3find
  252. xapi-rrd >= "1.9.0"
  253. yojson-five >= "3.0.0"
  254. yosqlite >= "0.2"
  255. yultracer
  256. zanuda
  257. zarr

Conflicts

None