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. aws-config
  10. aws-s3 < "4.5.1" | >= "4.8.0"
  11. awsm-codegen
  12. bap-radare2
  13. bitcoin >= "3.0"
  14. boulangerie
  15. builder-web >= "0.2.0"
  16. caisar
  17. calculon != "0.5"
  18. calculon-redis-lib
  19. calculon-web = "0.6"
  20. camelot >= "1.3.0"
  21. camels
  22. canary
  23. catala = "0.9.0" | >= "1.0.0~alpha"
  24. cb-check
  25. cbor >= "0.3"
  26. cconv-ppx
  27. chess_com_api
  28. colibrics
  29. comby-semantic
  30. commons
  31. containers >= "3.9"
  32. coq-lsp
  33. coq-of-ocaml
  34. coq-serapi >= "8.10.0+0.7.0" & < "8.20.0+0.20.0"
  35. crs >= "0.0.20250705"
  36. current_docker
  37. current_examples
  38. current_git
  39. current_github
  40. current_gitlab
  41. current_slack
  42. current_ssh
  43. current_web
  44. dap
  45. daypack-lib
  46. dblp-api
  47. decoders-yojson >= "0.7.0"
  48. devkit
  49. docfd >= "2.1.0"
  50. docker-api >= "0.2.2"
  51. docker_hub
  52. dot-merlin-reader < "4.9"
  53. dream
  54. dream-inertia
  55. dune-cargo-build
  56. dune-release >= "1.4.0"
  57. dune_deps_extra
  58. eio_main >= "0.10"
  59. elasticsearch-cli = "0.5"
  60. elpi >= "3.3.1"
  61. fehu
  62. fiat-p256
  63. fit >= "1.2.0"
  64. forester >= "3.1.0"
  65. frama-c < "23.0" | >= "27.0~beta"
  66. fred
  67. frenetic
  68. fstar
  69. gapi-ocaml
  70. gdbprofiler
  71. gemini
  72. gendarme-json
  73. github != "4.0.0"
  74. github-data
  75. gitlab
  76. goblint-cil >= "1.8.0"
  77. gopcaml-mode-merlin < "0.0.6"
  78. gradescope_submit
  79. graphql < "0.9.0" | >= "0.14.0"
  80. graphql-async >= "0.14.0"
  81. graphql-cohttp >= "0.13.0"
  82. graphql-lwt >= "0.14.0"
  83. graphql_ppx
  84. gremlin
  85. guardian
  86. h2
  87. hacl_x25519
  88. handlebars-ml
  89. hilite < "0.3.0"
  90. hl_yaml
  91. hockmd
  92. horned_worm
  93. hpack
  94. hsluv
  95. httph
  96. huml
  97. huml-cli
  98. index-bench
  99. ip2location
  100. ip2locationio
  101. ip2whois
  102. irmin-graphql
  103. irmin-tezos
  104. jasmin
  105. jhupllib
  106. jose
  107. js_of_ocaml-compiler
  108. jsonrpc >= "1.23.1"
  109. jsonschema
  110. jsonschema2atd
  111. jupyter
  112. jupyter-kernel
  113. jwto
  114. kappa-library < "4.1.3"
  115. karamel
  116. kaun >= "1.0.0~alpha1"
  117. kremlin < "transition"
  118. kubecaml
  119. lablgtk3-extras >= "3.0.1"
  120. lambdapi
  121. learn-ocaml
  122. letsencrypt
  123. letters
  124. libsail
  125. lichess_api
  126. linol >= "0.2" & < "0.10"
  127. linol-eio
  128. linol-lwt
  129. lockfree >= "0.3.1"
  130. logs-async-reporter >= "1.3"
  131. lsp < "1.6.0" | >= "1.23.1"
  132. melange-json = "1.2.0"
  133. melange-json-native
  134. merlin != "4.5-411"
  135. metadb
  136. mirage-crypto-ec
  137. mjson
  138. monorobot
  139. mopsa
  140. multicore-bench
  141. mutaml
  142. nloge
  143. nsq
  144. obuilder
  145. ocaml-lsp-server < "1.10.5" | >= "1.18.0" & != "1.21.0-4.14" & != "1.23.0"
  146. ocaml-protoc-plugin >= "6.1.0"
  147. ocaml_db_model
  148. ocaml_pgsql_model
  149. ocamleditor >= "1.15.2-ocaml414"
  150. ocsigen-start
  151. odoc >= "3.0.0"
  152. odoc-driver
  153. oframl
  154. oidc
  155. ojs-base
  156. ojs_base
  157. ometrics < "0.2.0"
  158. openai-gym
  159. openapi
  160. openapi_router
  161. opencage
  162. openstellina
  163. opium >= "0.19.0"
  164. oraft
  165. orun
  166. osh
  167. ozulip
  168. pa_ppx < "0.14" | >= "0.19"
  169. pandoc
  170. pbrt_yojson
  171. pds-reachability >= "0.2.3"
  172. petr4
  173. pgn_parser
  174. phylogenetics >= "0.2.0"
  175. piece_rope
  176. pkcs11-driver >= "1.0.0"
  177. ppx_deriving_jsonschema
  178. ppx_deriving_yojson < "3.6.1"
  179. ppx_protocol_conv_json < "5.0.0" | >= "5.2.1"
  180. ppx_yojson
  181. ppx_yojson_conv < "v0.13.0"
  182. ppx_yojson_conv_lib
  183. ppxlib-tools >= "0.37.0"
  184. prof_spacetime
  185. qmp >= "0.19.0"
  186. quests
  187. r2pipe
  188. radare2
  189. rdf
  190. records = "0.6.0" | >= "1.0.0"
  191. repr-bench
  192. rocq-devtools
  193. rpclib
  194. rungen
  195. rust-staticlib-gen
  196. SZXX
  197. safemoney
  198. saga
  199. sail < "0.15"
  200. saturn
  201. saturn_lockfree
  202. satyrographos != "0.0.2.7" & < "0.0.2.13"
  203. savvy
  204. semver2
  205. serde_json
  206. sihl < "0.2.0" | >= "0.3.0~rc2"
  207. sihl-core
  208. slack
  209. slug
  210. smaws-lib
  211. smtml >= "0.7.0"
  212. snf_mcp < "0.2.1"
  213. spotify-web-api
  214. starred_ml
  215. swagger
  216. talon
  217. tdigest < "2.1.0"
  218. textmate-language >= "0.3.4"
  219. textrazor >= "0.1.1"
  220. tezos-context-hash-irmin
  221. tidy_email_sendgrid
  222. timedesc < "0.8.0"
  223. timedesc-json
  224. timere < "0.4.0"
  225. user-agent-parser
  226. vecosek
  227. vercel
  228. vscoq-language-server
  229. vsrocq-language-server
  230. wasm_of_ocaml-compiler
  231. webauthn
  232. why3find
  233. xapi-rrd >= "1.9.0"
  234. yojson-five >= "3.0.0"
  235. yosqlite >= "0.2"
  236. zanuda
  237. zarr

Conflicts

None