package lwt

  1. Overview
  2. Docs
Promises and event-driven I/O

Install 

dune-project
 Dependency

github.com Edit opam file Versions (34)

Authors

  1. J
    Jérôme Vouillon
  2. J
    Jérémie Dimino

Maintainers

  1. R
    Raphaël Proust <code@bnwr.net>
  2. Anton Bachin

Sources

6.1.2.tar.gz
md5=00bc7eb2772a28530f7365a7040f0c4f
sha512=a4737a2fc44aaeedca46ec6134c07013d5cf44039a988a6e79a40715a53e43601d4c91bbf11a8e89540528d912b8fa487e3068465c136c1156a872258eb3443b

Description

A promise is a value that may become determined in the future.

Lwt provides typed, composable promises. Promises that are resolved by I/O are resolved by Lwt in parallel.

Meanwhile, OCaml code, including code creating and waiting on promises, runs in a single thread by default. This reduces the need for locks or other synchronization primitives. Code can be run in parallel on an opt-in basis.

Published: 29 Apr 2026

Dependencies (5)

  1. ocplib-endian
  2. dune-configurator
  3. cppo build & >= "1.1"
  4. ocaml >= "4.14"
  5. dune >= "3.18"

Dev Dependencies (2)

  1. odoc with-doc & >= "2.3"
  2. ocamlfind dev & >= "1.7.3-1"

  1. 0install >= "2.15.1"
  2. aches-lwt
  3. activitypub
  4. albatross
  5. alcotest-lwt
  6. alcotest-mirage
  7. ambient-context-lwt
  8. amqp-client >= "1.1.0"
  9. amqp-client-lwt
  10. angstrom-lwt-unix >= "0.11.0"
  11. anthill
  12. anycache-lwt
  13. archi-lwt
  14. arp
  15. awa-mirage
  16. aws-lwt
  17. aws-s3-lwt >= "4.8.1"
  18. awskit-lwt
  19. awskit-lwt-unix
  20. awskit-s3-lwt
  21. awskit-s3-lwt-unix
  22. awsm-lwt
  23. awso-lwt
  24. azure-cosmos-db < "0.4.0"
  25. azure-cosmos-db-lwt
  26. balancer
  27. bastet_lwt
  28. bimage-lwt
  29. bistro
  30. bizowie-api
  31. brisk-reconciler
  32. builder
  33. builder-web
  34. bun >= "0.3.3"
  35. cachet-lwt
  36. calculon
  37. caldav
  38. camltc
  39. canary
  40. capnp-rpc-lwt < "2.0"
  41. capnp-rpc-unix < "2.1"
  42. caqti-lwt
  43. caqti-mirage
  44. carton < "1.0.0"
  45. carton-git
  46. carton-lwt
  47. catala-format >= "0.2.0"
  48. cf-lwt
  49. chamelon
  50. chamelon-unix
  51. chamo
  52. charrua-client
  53. charrua-unix
  54. chess_com_api
  55. ciao_lwt
  56. clz
  57. cmdtui-lambda-term
  58. coap
  59. coap-server-lwt
  60. cohttp-curl-lwt
  61. cohttp-lwt
  62. cohttp-lwt-jsoo
  63. cohttp-lwt-unix
  64. cohttp-mirage
  65. cohttp-server-lwt-unix
  66. comby
  67. comby-semantic
  68. conan-lwt
  69. conduit-lwt
  70. conduit-lwt-unix
  71. cowabloga
  72. crunch
  73. cstruct-lwt
  74. csv-lwt
  75. ctypes >= "0.15.0" & < "0.21.1"
  76. ctypes-foreign >= "0.21.1"
  77. curl_lwt
  78. current
  79. current-albatross-deployer
  80. current_docker
  81. current_examples
  82. current_git
  83. current_github
  84. current_gitlab
  85. current_ocluster
  86. current_rpc
  87. current_slack
  88. current_web
  89. dap
  90. data-encoding < "0.1.1"
  91. devkit >= "1.2"
  92. distributed-lwt
  93. dkim-bin < "0.8.0"
  94. dkim-lwt-unix
  95. dkim-mirage
  96. dlm
  97. dmarc
  98. dns-certify
  99. dns-cli
  100. dns-client < "7.0.3"
  101. dns-client-lwt
  102. dns-client-mirage
  103. dns-forward
  104. dns-forward-lwt-unix
  105. dns-lwt
  106. dns-mirage
  107. dns-resolver
  108. dns-server
  109. dns-stub
  110. dnsrobot
  111. dnssd
  112. docker_hub
  113. docteur >= "0.0.2"
  114. docteur-solo5
  115. docteur-unix >= "0.0.5"
  116. doi2bib
  117. dream
  118. dream-httpaf
  119. dream-pure
  120. dream-serve < "1.0.1"
  121. dropbox
  122. dune >= "3.17.2"
  123. dune-rpc-lwt
  124. earlybird
  125. elasticsearch-cli
  126. emoji = "2.0.0"
  127. equinoxe
  128. ethernet
  129. ez_api >= "1.2.0" & < "3.0.0"
  130. ezcurl-lwt
  131. ezjs_min < "0.2"
  132. ezjsonm-lwt
  133. ezresto
  134. faraday-lwt
  135. faraday-lwt-unix
  136. fat-filesystem
  137. fiber-lwt
  138. fsevents-lwt
  139. fswatch_lwt
  140. gdbprofiler
  141. git
  142. git-cohttp
  143. git-cohttp-unix
  144. git-kv >= "0.2.0"
  145. git-mirage
  146. git-paf
  147. git-unix >= "3.2.0"
  148. github
  149. github-hooks
  150. github-unix >= "4.4.0"
  151. gitlab-unix
  152. gitlab_pipeline_notifier
  153. gluten-lwt
  154. gluten-lwt-unix < "0.4.0"
  155. gluten-mirage < "0.4.0"
  156. granary
  157. granary_repl
  158. graphql-lwt
  159. gremlin
  160. grpc-lwt
  161. guardian
  162. gufo
  163. h1
  164. h1-lwt-unix
  165. h2-lwt
  166. h2-lwt-unix < "0.10.0"
  167. h2-mirage
  168. happy-eyeballs-lwt
  169. happy-eyeballs-mirage
  170. hidapi-lwt
  171. hiredis >= "0.6"
  172. hl_yaml
  173. hockmd
  174. http-lwt-client
  175. http-mirage-client
  176. http-multipart-formdata >= "2.0.0" & < "3.0.0"
  177. httpaf-lwt-unix
  178. httpun-lwt
  179. httpun-mirage
  180. httpun-ws-lwt
  181. hvsock
  182. i3ipc
  183. influxdb-lwt
  184. inotify >= "2.4"
  185. inquire < "0.3.0"
  186. interface-prime-lwt
  187. ip2location
  188. ip2locationio
  189. ip2whois
  190. ipv6-multicast-lwt
  191. irc-client-lwt
  192. irc-client-lwt-ssl
  193. irc-client-tls
  194. irmin
  195. irmin-bench
  196. irmin-chunk
  197. irmin-cli
  198. irmin-client
  199. irmin-containers
  200. irmin-fs
  201. irmin-git
  202. irmin-graphql
  203. irmin-http
  204. irmin-indexeddb
  205. irmin-layers
  206. irmin-mirage-git
  207. irmin-mirage-graphql
  208. irmin-pack
  209. irmin-server
  210. irmin-test
  211. irmin-unix
  212. irmin-watcher
  213. joolog
  214. jose < "0.9.0"
  215. js_of_ocaml-lwt
  216. jsoo_broadcastchannel
  217. jsoo_storage
  218. jupyter
  219. jupyter-kernel
  220. kafka < "0.5"
  221. kafka_lwt
  222. kappa-library
  223. ke >= "0.5"
  224. kinetic-client
  225. kubecaml
  226. lambda-runtime
  227. lambda-term >= "3.3.3"
  228. lambda_streams_lwt
  229. launchd
  230. ldp
  231. learn-ocaml
  232. learn-ocaml-client
  233. ledgerwallet >= "0.4.0"
  234. letsencrypt < "2.0.0"
  235. letsencrypt-app
  236. letsencrypt-dns < "2.0.0"
  237. letters
  238. lichess_api
  239. links
  240. llama
  241. lru_cache
  242. lwt-canceler
  243. lwt-dllist
  244. lwt-exit
  245. lwt-parallel
  246. lwt-pipe
  247. lwt-pipeline
  248. lwt-watcher
  249. lwt_camlp4
  250. lwt_direct >= "6.0.0"
  251. lwt_domain != "0.2.0"
  252. lwt_eio >= "0.6"
  253. lwt_ppx >= "6.0.0"
  254. lwt_react
  255. lwt_retry
  256. lwt_ssl
  257. mariadb >= "1.2.0"
  258. markdown_monolith
  259. markup = "0.7.6"
  260. markup-lwt
  261. mdx
  262. mechaml
  263. mehari-lwt-unix
  264. mehari-mirage
  265. memtrace-mirage
  266. metrics-influx
  267. metrics-lwt
  268. metrics-unix
  269. migra
  270. mimic
  271. mindstorm-lwt
  272. mirage < "4.0.0"
  273. mirage-block >= "2.0.1"
  274. mirage-block-ccm
  275. mirage-block-combinators
  276. mirage-block-lwt
  277. mirage-block-partition
  278. mirage-block-ramdisk
  279. mirage-block-solo5
  280. mirage-block-unikraft
  281. mirage-block-unix >= "2.14.2"
  282. mirage-block-xen
  283. mirage-channel >= "4.0.1"
  284. mirage-channel-lwt
  285. mirage-clock-lwt
  286. mirage-clock-unix < "4.2.0"
  287. mirage-console-lwt
  288. mirage-crypto-rng < "0.11.3"
  289. mirage-crypto-rng-lwt
  290. mirage-crypto-rng-mirage
  291. mirage-device >= "2.0.0"
  292. mirage-flow >= "3.0.0"
  293. mirage-flow-combinators
  294. mirage-flow-lwt
  295. mirage-flow-unix
  296. mirage-fs >= "4.0.0"
  297. mirage-fs-lwt
  298. mirage-kv >= "3.0.1"
  299. mirage-kv-lwt
  300. mirage-kv-unix
  301. mirage-net >= "4.0.0"
  302. mirage-net-lwt
  303. mirage-net-macosx
  304. mirage-net-solo5
  305. mirage-net-unikraft
  306. mirage-net-unix
  307. mirage-net-xen
  308. mirage-profile
  309. mirage-protocols >= "7.0.0"
  310. mirage-protocols-lwt
  311. mirage-qubes
  312. mirage-qubes-ipv4
  313. mirage-runtime
  314. mirage-sleep
  315. mirage-solo5
  316. mirage-stack = "3.0.0"
  317. mirage-stack-lwt
  318. mirage-time >= "3.0.0"
  319. mirage-time-lwt
  320. mirage-time-unix
  321. mirage-types-lwt
  322. mirage-unikraft
  323. mirage-unix
  324. mirage-vnetif
  325. mirage-xen
  326. monorobot
  327. mqtt
  328. mrmime >= "0.5.0"
  329. multipart-form-data
  330. multipart_form >= "0.2.0" & < "0.4.0"
  331. multipart_form-cohttp-lwt < "0.6.0"
  332. multipart_form-lwt
  333. naboris
  334. nbd >= "4.0.3"
  335. nbd-tool
  336. nbd-unix
  337. neo4j_bolt
  338. nottui-lwt
  339. notty-community
  340. nproc
  341. nsq
  342. obuilder
  343. obus >= "1.2.1"
  344. ocaml-ai-sdk
  345. ocluster
  346. ocluster-api
  347. ocluster-worker
  348. ocplib-resto
  349. ocsigenserver
  350. ocsipersist
  351. ocsipersist-dbm
  352. ocsipersist-lib
  353. ocsipersist-pgsql
  354. ocsipersist-sqlite
  355. oframl
  356. ojs_base
  357. omigrate
  358. oneffs
  359. opam-check-npm-deps >= "4.1.0"
  360. opam-publish >= "3.0.0"
  361. opencage
  362. opentelemetry-client-cohttp-lwt
  363. opentelemetry-client-ocurl-lwt
  364. opentelemetry-cohttp-lwt >= "0.4"
  365. opentelemetry-lwt
  366. opium
  367. opium-graphql
  368. opium_kernel
  369. opomodoro
  370. order-i3-xfce
  371. ordma
  372. oskel >= "0.3.0"
  373. ounit-lwt < "2.2.0"
  374. ounit2-lwt
  375. owork
  376. ozulip
  377. paf
  378. paf-cohttp
  379. passage < "0.1.8"
  380. pcap-format < "0.5.2"
  381. petrol
  382. pgn_parser
  383. pgx_lwt
  384. pgx_lwt_mirage
  385. pgx_lwt_unix < "2.0"
  386. piaf < "0.2.0"
  387. picos >= "0.3.0" & < "0.5.0"
  388. picos_meta
  389. plebeia >= "2.0.0"
  390. plotkicadsch
  391. posix-getopt >= "4.0.2"
  392. ppx_defer >= "0.4.0"
  393. ppx_deriving_rpc
  394. ppx_rapper_lwt
  395. proc-smaps
  396. prof_spacetime
  397. prometheus
  398. prometheus-app
  399. promise_jsoo_lwt
  400. protocol-9p
  401. protocol-9p-unix
  402. proton
  403. pxshot
  404. qcow
  405. qcow-stream
  406. qcow-tool
  407. qcow-types
  408. qdrant < "0.2.0"
  409. qfs
  410. quests
  411. quickterface
  412. rawlink < "2.1"
  413. rawlink-lwt
  414. rdf_json_ld
  415. rdf_lwt
  416. redis-lwt
  417. reparse-lwt
  418. reparse-lwt-unix
  419. resource-pooling
  420. resp
  421. resp-mirage >= "0.10.0"
  422. resp-unix >= "0.10.0"
  423. resto
  424. resto-cohttp-client = "0.4"
  425. resto-cohttp-server = "0.4"
  426. resto-directory = "0.4"
  427. ringo-lwt
  428. river
  429. rock
  430. rpclib-js
  431. rpclib-lwt
  432. SZXX < "4.0.0"
  433. sanddb
  434. scgi
  435. sendmail-lwt
  436. sendmail-mirage
  437. serial
  438. server-reason-react
  439. session-cohttp-lwt
  440. session-cookie-lwt
  441. session-postgresql-lwt
  442. sessions
  443. shared-block-ring
  444. shared-memory-ring-lwt
  445. sherlodoc
  446. sihl < "0.2.0"
  447. slack
  448. slacko
  449. slipshow
  450. smtml >= "0.7.0"
  451. speed
  452. spin < "0.8.0"
  453. spoke
  454. statocaml
  455. stk
  456. stog
  457. swapfs
  458. syguslib-utils
  459. syndic >= "1.4" & < "1.6.0"
  460. tar-mirage
  461. tar-unix
  462. tcpip
  463. telegraml
  464. terminus
  465. testcontainers
  466. testo-lwt
  467. tidy_email
  468. tls >= "0.10.6" & < "0.16.0"
  469. tls-lwt
  470. tls-mirage
  471. tube
  472. tuntap
  473. twirp_cohttp_lwt_unix
  474. uring
  475. uspf
  476. uspf-lwt
  477. uspf-mirage
  478. utcp
  479. utop
  480. uwt
  481. vchan
  482. vchan-unix
  483. vchan-xen
  484. vercel
  485. vhd-format-lwt
  486. vmnet
  487. vue-jsoo < "0.3"
  488. wayland < "2.0"
  489. webauthn
  490. xen-evtchn
  491. xen-evtchn-unix
  492. xen-gnt
  493. xen-gnt-unix
  494. xenstore
  495. xenstore-tool
  496. xenstore_transport
  497. xlsx2csv
  498. yocaml_git
  499. yocaml_unix < "2.0.0"
  500. zarr-lwt
  501. zmq-lwt >= "5.2.1"

Conflicts

None