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About Clozure CL

Clozure CL is an open source Common Lisp implementation that runs on PowerPC hardware under Mac OS X and Linux, and on x86-64 hardware under Mac OS X, Linux, and FreeBSD. A port to 32-bit x86 is progressing well; a port to 64-bit Windows is also pretty far along. There's also a Solaris x86-64 port that is mostly working.

Some distinguishing features of the implementation include:

  • fast compilation speed
  • native OS threads
  • precise, generational, compacting garbage collector
  • convenient foreign-function interface

Clozure CL used to be called OpenMCL. It is also sometimes called CCL. You will see the three names being used interchangeably.

Getting Clozure CL

Please see  Obtaining, Installing, and Running Clozure CL for complete instructions.

The most recent released version of Clozure CL is 1.2. Archives of Clozure CL 1.2 are available via anonymous ftp at

After installing CCL, read about getting updates and bug fixes.


The Clozure CL manual is available on the web at or As of Clozure CL 1.2, the DocBook sources for the manual are included with the distribution.


Mailing Lists

There are two CCL-related mailing lists hosted at Click on a list's link to subscribe or to view archived messages.


Everyone interested in Clozure CL is welcome to participate in #ccl on The  channel logs are available.

Paid Support

 Clozure Associates provides commercial support and consulting services for Clozure CL as well as other Common Lisp implementations. These services can range from helping you debug your software to adding extensions to CCL, to providing several full time Lisp programmers to help you build your application. Please contact us at business@… for more information.

Starting Points

CCL Basics

Contributing to CCL

In-Depth CCL

Orient Yourself to Clozure CL Culture