Welcome to the Cloudy home page!

Cloudy is a spectral synthesis code designed to simulate conditions in interstellar matter under a broad range of conditions. It is provided for general use under an open source License.

Please post questions or problems on the Cloudy discussion board. Updates to Cloudy will be announced on that board.

Our user forum has moved to this site. Yahoo have shut down their old groups site.

C17.03, is released. This paper discusses what is new. Follow the StepByStep instructions for downloading and installing the code, or go straight to the DownloadLinks page to obtain it. NewC17 explains improvements and changes.

The next Cloudy workshop was scheduled for Athens, Greece, June 15-19, 2020 but it delayed due to the virus. For more details visit the workshop website and join the workshop user group at to receive notices of developments.

Getting started with Cloudy

The VideoPage has several videos showing how to build and run Cloudy.

StepByStep instructions for downloading and installing the release version, and running the code on various platforms.

Or you can go straight to the DownloadLinks page.

StellarAtmospheres in Cloudy are now very flexible. They are described on this web site rather than in Hazy.

KnownProblems are described on this page.

HotFixes are small corrections to the source that fix problems discovered after the current stable version was released.

The RevisionHistory pages list changes and new features in past, current and the next versions.

Frequently asked questions are on the FaqPage

More information about Cloudy

A list of Cloudy papers and documentation can be found in this link

Old versions of Cloudy are on the CloudyOld page

The DownloadLinks page gives links to download the current version of the code, and trial versions if they exist.

Acknowledgments for help with Cloudy are on the AcknowledgmentsPage

Outside pages related to Cloudy or related physics

ContributedMaterial - codes and spectra contributed by others.

A list of typos in AGN3 is posted here. (updated 2016 August)

A very old page giving miscellaneous information, including the following: people involved in its development, the code's history and style convention, computing at Cambridge in the 1970's, what the version numbers mean, the distinction between notation such as C+2 vs C III, how to call C from Fortran. Software contributed to drive Cloudy, other spectral synthesis codes, development software, atomic data, Kentucky, meetings on spectroscopy, and a collection of cloud images from across the internet.

The web page for the 1994 Lexington meeting on photoionization and shock models.


These are donated scripts that help use Cloudy more efficiently. Do you have a useful script? If so please send a link to a page describing it to the Cloudy discussion board.


Meta wiki

Discussion about the wiki, trac, etc is at MetaWiki

For a complete list of local wiki pages, see TitleIndex.

The trac page on wiki formatting

Last modified 11 months ago Last modified on 2022-05-06T19:12:48Z