First alpha release of OCaml 5.5.0

Florian Angeletti <[email protected]> Fri, 27 Feb 2026 14:59:56 +0100 (CET)
Newsgroups gmane.comp.lang.caml.inria
Message-ID <[email protected]>
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Dear OCaml users, 

Four months after the release of OCaml 5.4.0, the set of new features for the 
future version 5.5.0 of OCaml has been frozen. We are thus happy to announce 
the first alpha release for OCaml 5.5.0. 

This alpha version is here to help fellow hackers join us early in our bug 
hunting and opam ecosystem fixing fun (see below for the installation 
instructions). More information about the release process is available 
at https://github.com/ocaml/ocaml/blob/trunk/release-info/introduction.md. 

The progress on stabilising the ecosystem is tracked on the 
"opam readiness for 5.5.0 meta-issue" at 

- https://github.com/ocaml/opam-repository/issues/29463 

There is also a companion alpha opam repository available for this alpha release 

opam repo add alpha git+https://github.com/kit-ty-kate/opam-alpha-repository.git 

which contains in-progress alpha releases of opam packages that are being updated for 
OCaml 5.5.0 . 

The full release is expected between May and June. There are more information 
available in the prospective calendar at 

- https://github.com/ocaml/ocaml/blob/trunk/release-info/calendar.md . 

If you find any bugs, please report them on OCaml's issue tracker: 

- https://github.com/ocaml/ocaml/issues 

If you are interested in the ongoing list of new features and bug fixes, the 
updated change log for OCaml 5.5.0 is available on GitHub at 

- https://github.com/ocaml/ocaml/blob/5.5/Changes 

Happy hacking, 
Florian Angeletti for the OCaml team 

Installation Instructions 
------------------------------ 

The base compiler can be installed as an opam switch with the following commands 
on opam 2.1 and later: 

opam update 
opam switch create 5.5.0~alpha1 

The source code for the alpha is also available at these addresses: 

* GitHub: https://github.com/ocaml/ocaml/archive/5.5.0-alpha1.tar.gz 
* OCaml archives at Inria: https://caml.inria.fr/pub/distrib/ocaml-5.5/ocaml-5.5.0~alpha1.tar.gz 

Fine-Tuned Compiler Configuration 
---------------------------------------------- 

If you want to tweak the configuration of the compiler, you can switch to the option variant with: 


opam update 
opam switch create <switch_name> ocaml-variants.5.5.0~alpha1+options <option_list> 


where `option_list` is a space separated list of `ocaml-option-*` packages. For instance, for a flambda and no-flat-float-array switch: 


opam switch create 5.5.0~alpha1+flambda+nffa ocaml-variants.5.5.0~alpha1+options ocaml-option-flambda ocaml-option-no-flat-float-array 


All available options can be listed with `opam search ocaml-option`. 




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<html><body><div style=3D"font-family: arial, helvetica, sans-serif; font-s=
ize: 12pt; color: #000000"><div>Dear OCaml users,<br><br>Four months after =
the release of OCaml 5.4.0, the set of new features for the<br>future versi=
on 5.5.0 of OCaml has been frozen. We are thus happy to announce<br>the fir=
st alpha release for OCaml 5.5.0.<br><br>This alpha version is here to help=
 fellow hackers join us early in our bug<br>hunting and opam ecosystem fixi=
ng fun (see below for the installation<br>instructions). More information a=
bout the release process is available<br>at https://github.com/ocaml/ocaml/=
blob/trunk/release-info/introduction.md.<br><br>The progress on stabilising=
 the ecosystem is tracked on the<br>"opam readiness for 5.5.0 meta-issue" a=
t<br><br>&nbsp; - https://github.com/ocaml/opam-repository/issues/29463<br>=
<br>There is also a companion alpha opam repository available for this alph=
a release<br><br>&nbsp; &nbsp; &nbsp; opam repo add alpha git+https://githu=
b.com/kit-ty-kate/opam-alpha-repository.git<br><br>which contains in-progre=
ss alpha releases of opam packages that are being updated for<br>OCaml 5.5.=
0 .<br><br>The full release is expected between May and June. There are mor=
e information<br>available in the prospective calendar at<br><br>&nbsp; - h=
ttps://github.com/ocaml/ocaml/blob/trunk/release-info/calendar.md .<br><br>=
If you find any bugs, please report them on OCaml's issue tracker:<br><br>&=
nbsp; - https://github.com/ocaml/ocaml/issues<br><br>If you are interested =
in the ongoing list of new features and bug fixes, the<br>updated change lo=
g for OCaml 5.5.0 is available on GitHub at<br><br>&nbsp; - https://github.=
com/ocaml/ocaml/blob/5.5/Changes<br><br>Happy hacking,<br>Florian Angeletti=
 for the OCaml team<br><br>Installation Instructions<br>-------------------=
-----------<br><br>The base compiler can be installed as an opam switch wit=
h the following commands<br>on opam 2.1 and later:<br><br>&nbsp; &nbsp; opa=
m update<br>&nbsp; &nbsp; opam switch create 5.5.0~alpha1<br><br>The source=
 code for the alpha is also available at these addresses:<br><br>* GitHub: =
https://github.com/ocaml/ocaml/archive/5.5.0-alpha1.tar.gz<br>* OCaml archi=
ves at Inria: https://caml.inria.fr/pub/distrib/ocaml-5.5/ocaml-5.5.0~alpha=
1.tar.gz<br><br>Fine-Tuned Compiler Configuration<br>----------------------=
------------------------<br><br>If you want to tweak the configuration of t=
he compiler, you can switch to the option variant with:<br><br><br>&nbsp; &=
nbsp; opam update<br>&nbsp; &nbsp; opam switch create &lt;switch_name&gt; o=
caml-variants.5.5.0~alpha1+options &lt;option_list&gt;<br><br><br>where `op=
tion_list` is a space separated list of `ocaml-option-*` packages. For inst=
ance, for a flambda and no-flat-float-array switch:<br><br><br>&nbsp; &nbsp=
; opam switch create 5.5.0~alpha1+flambda+nffa ocaml-variants.5.5.0~alpha1+=
options ocaml-option-flambda ocaml-option-no-flat-float-array<br><br><br>Al=
l available options can be listed with `opam search ocaml-option`.<br><br><=
br><br data-mce-bogus=3D"1"></div></div></body></html>
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