---
title: "OCaml 5.5.0 released"
url: https://daily.dev/posts/ocaml-5-5-0-released-nq6jzdbdm
source_url: https://discuss.ocaml.org/t/ocaml-5-5-0-released/18265
type: article
source: "Lobsters"
published: 2026-06-21T16:14:32.798Z
updated: 2026-06-21T16:15:00.862Z
tags: ["functional-programming", "compiler", "ocaml"]
reading_time: 33
upvotes: 0
comments: 0
language: en
---

> ## Documentation Index
> Fetch the complete documentation index at: https://daily.dev/llms.txt
> Use this file to discover all available pages before exploring further.

# OCaml 5.5.0 released

**[Lobsters](https://daily.dev/sources/lobsters)** · 33 min read · 0 upvotes · 0 comments

## Summary

OCaml 5.5.0 has been released with several significant language and runtime improvements. Key highlights include module-dependent functions (modular explicits) enabling lightweight functors as function arguments, a relocatable compiler that can be moved without breaking bytecode runtime compatibility, higher-rank polymorphic function arguments via explicit type annotations, and an expanded String standard library with search/replace/split functions using the 2-way string matching algorithm. The release also introduces generalized local definitions, external types for better FFI integration with GADTs, and GC improvements including a new sweep-only phase and idle phase. Additionally, around 60 new standard library functions, ~90 improvements, ~40 bug fixes, and Windows concurrency primitives now use WinAPI instead of Winpthreads.

## Full article

daily.dev links to this article rather than hosting it. Read it at the original source: <https://discuss.ocaml.org/t/ocaml-5-5-0-released/18265>

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---

Tags: [#functional-programming](https://daily.dev/tags/functional-programming), [#compiler](https://daily.dev/tags/compiler), [#ocaml](https://daily.dev/tags/ocaml)

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