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. index-bench
  97. ip2location
  98. ip2locationio
  99. ip2whois
  100. irmin-graphql
  101. irmin-tezos
  102. jasmin
  103. jhupllib
  104. jose
  105. js_of_ocaml-compiler
  106. jsonrpc >= "1.23.1"
  107. jsonschema
  108. jsonschema2atd
  109. jupyter
  110. jupyter-kernel
  111. jwto
  112. kappa-library < "4.1.3"
  113. karamel
  114. kaun >= "1.0.0~alpha1"
  115. kremlin < "transition"
  116. kubecaml
  117. lablgtk3-extras >= "3.0.1"
  118. lambdapi
  119. learn-ocaml
  120. letsencrypt
  121. letters
  122. libsail
  123. lichess_api
  124. linol >= "0.2" & < "0.10"
  125. linol-eio
  126. linol-lwt
  127. lockfree >= "0.3.1"
  128. logs-async-reporter >= "1.3"
  129. lsp < "1.6.0" | >= "1.23.1"
  130. melange-json = "1.2.0"
  131. melange-json-native
  132. merlin != "4.5-411"
  133. metadb
  134. mirage-crypto-ec
  135. mjson
  136. monorobot
  137. mopsa
  138. multicore-bench
  139. mutaml
  140. nloge
  141. nsq
  142. obuilder
  143. ocaml-lsp-server < "1.10.5" | >= "1.18.0" & != "1.21.0-4.14" & != "1.23.0"
  144. ocaml-protoc-plugin >= "6.1.0"
  145. ocaml_db_model
  146. ocaml_pgsql_model
  147. ocamleditor >= "1.15.2-ocaml414"
  148. ocsigen-start
  149. odoc >= "3.0.0"
  150. odoc-driver
  151. oframl
  152. oidc
  153. ojs-base
  154. ojs_base
  155. ometrics < "0.2.0"
  156. openai-gym
  157. openapi
  158. openapi_router
  159. opencage
  160. openstellina
  161. opium >= "0.19.0"
  162. oraft
  163. orun
  164. osh
  165. ozulip
  166. pa_ppx < "0.14" | >= "0.19"
  167. pandoc
  168. pbrt_yojson
  169. pds-reachability >= "0.2.3"
  170. petr4
  171. pgn_parser
  172. phylogenetics >= "0.2.0"
  173. piece_rope
  174. pkcs11-driver >= "1.0.0"
  175. ppx_deriving_jsonschema
  176. ppx_deriving_yojson < "3.6.1"
  177. ppx_protocol_conv_json < "5.0.0" | >= "5.2.1"
  178. ppx_yojson
  179. ppx_yojson_conv < "v0.13.0"
  180. ppx_yojson_conv_lib
  181. ppxlib-tools >= "0.37.0"
  182. prof_spacetime
  183. qmp >= "0.19.0"
  184. quests
  185. r2pipe
  186. radare2
  187. rdf
  188. records = "0.6.0" | >= "1.0.0"
  189. repr-bench
  190. rocq-devtools
  191. rpclib
  192. rungen
  193. rust-staticlib-gen
  194. SZXX
  195. safemoney
  196. saga
  197. sail < "0.15"
  198. saturn
  199. saturn_lockfree
  200. satyrographos != "0.0.2.7" & < "0.0.2.13"
  201. savvy
  202. semver2
  203. serde_json
  204. sihl < "0.2.0" | >= "0.3.0~rc2"
  205. sihl-core
  206. slack
  207. slug
  208. smaws-lib
  209. smtml >= "0.7.0"
  210. snf_mcp < "0.2.1"
  211. spotify-web-api
  212. starred_ml
  213. swagger
  214. talon
  215. tdigest < "2.1.0"
  216. textmate-language >= "0.3.4"
  217. textrazor >= "0.1.1"
  218. tezos-context-hash-irmin
  219. tidy_email_sendgrid
  220. timedesc < "0.8.0"
  221. timedesc-json
  222. timere < "0.4.0"
  223. user-agent-parser
  224. vecosek
  225. vercel
  226. vscoq-language-server
  227. vsrocq-language-server
  228. wasm_of_ocaml-compiler
  229. webauthn
  230. why3find
  231. xapi-rrd >= "1.9.0"
  232. yojson-five >= "3.0.0"
  233. yosqlite >= "0.2"
  234. zanuda
  235. zarr

Conflicts

None