The Cathedral and the Bazaar

Eric S. Raymond
The Cathedral and the Bazaar
Eric Steven Raymond
Thyrsus Enterprises

This is version 3.0
Copyright © 2000 Eric S. Raymond
Permission is granted to copy, distribute and/or modify this document under the terms of
the Open Publication License, version 2.0.
$Date: 2002/08/02 09:02:14 $
Revision History
Revision 1.57 11 September 2000 esr New major section ``How Many Eyeballs Tame
Revision 1.52 28 August 2000 esr MATLAB is a reinforcing parallel to Emacs.
Corbato— & Vyssotsky got it in 1965.
Revision 1.51 24 August 2000 esr First DocBook version. Minor updates to Fall 2000 on
the time-sensitive material.
Revision 1.49 5 May 2000 esr Added the HBS note on deadlines and scheduling.
Revision 1.51 31 August 1999 esr This the version that O'Reilly printed in the first
edition of the book.
Revision 1.45 8 August 1999 esr Added the endnotes on the Snafu Principle,
(pre)historical examples of bazaar development, and originality in the bazaar.
Revision 1.44 29 July 1999 esr Added the ``On Management and the Maginot Line''
section, some insights about the usefulness of bazaars for exploring design space, and
substantially improved the Epilog.
Revision 1.40 20 Nov 1998 esr Added a correction of Brooks based on the Halloween
Revision 1.39 28 July 1998 esr I removed Paul Eggert's 'graph on GPL vs. bazaar in
response to cogent aguments from RMS on

Revision 1.31 February 10 1998 esr Added ``Epilog: Netscape Embraces the Bazaar!''
Revision 1.29 February 9 1998 esr Changed ``free software'' to ``open source''.
Revision 1.27 18 November 1997 esr Added the Perl Conference anecdote.
Revision 1.20 7 July 1997 esr Added the bibliography.
Revision 1.16 21 May 1997 esr First official presentation at the Linux Kongress.
I anatomize a successful open-source project, fetchmail, that was run as a deliberate test
of the surprising theories about software engineering suggested by the history of Linux. I
discuss these theories in terms of two fundamentally different development styles, the
``cathedral'' model of most of the commercial world versus the ``bazaar'' model of the
Linux world. I show that these models derive from opposing assumptions about the
nature of the software-debugging task. I then make a sustained argument from the Linux
experience for the proposition that ``Given enough eyeballs, all bugs are shallow'',
suggest productive analogies with other self-correcting systems of selfish agents, and
conclude with some exploration of the implications of this insight for the future of
Table of Contents
* The Cathedral and the Bazaar
* The Mail Must Get Through
* The Importance of Having Users
* Release Early, Release Often
* How Many Eyeballs Tame Complexity
* When Is a Rose Not a Rose?
* Popclient becomes Fetchmail
* Fetchmail Grows Up
* A Few More Lessons from Fetchmail
* Necessary Preconditions for the Bazaar Style
* The Social Context of Open-Source Software
* On Management and the Maginot Line

* Epilog: Netscape Embraces the Bazaar
* Notes
* Bibliography
* Acknowledgements
The Cathedral and the Bazaar
Linux is subversive. Who would have thought even five years ago (1991) that a
world-class operating system could coalesce as if by magic out of part-time hacking by
several thousand developers scattered all over the planet, connected only by the tenuous
strands of the Internet?
Certainly not I. By the time Linux swam onto my radar screen in early 1993, I had
already been involved in Unix and open-source development for ten years. I was one of
the first GNU contributors in the mid-1980s. I had released a good deal of open-source
software onto the net, developing or co-developing several programs (nethack, Emacs's
VC and GUD modes, xlife, and others) that are still in wide use today. I thought I knew
how it was done.
Linux overturned much of what I thought I knew. I had been preaching the Unix gospel
of small tools, rapid prototyping and evolutionary programming for years. But I also
believed there was a certain critical complexity above which a more centralized, a priori
approach was required. I believed that the most important software (operating systems
and really large tools like the Emacs programming editor) needed to be built like
cathedrals, carefully crafted by individual wizards or small bands of mages working in
splendid isolation, with no beta to be released before its time.
Linus Torvalds's style of development-release early and often, delegate everything you
can, be open to the point of promiscuity-came as a surprise. No quiet, reverent
cathedral-building here-rather, the Linux community seemed to resemble a great babbling
bazaar of differing agendas and approaches (aptly symbolized by the Linux archive sites,
who'd take submissions from anyone) out of which a coherent and stable system could
seemingly emerge only by a succession of miracles.
The fact that this bazaar style seemed to work, and work well, came as a distinct shock.
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