Gecko Version Cross-Reference Chart - The Andrew Turnbull Mozilla Network

"Gecko" is the name of the layout engine that Mozilla Firefox and numerous other web browsers and other Internet software are built upon...the "underpinnings," if you will. Gecko was first demonstrated by Netscape in 1998, and originally titled "NGLayout" (or Next Generation Layout) in reference to the differences that set it apart from the rendering engine of Netscape 4.x and earlier releases.

Numerous revisions of the Gecko codebase have been implemented since then. Since 2000, the codebase version number has been identifiable within the user agent string in a form similar to "Mozilla/5.0 (Windows; U; Win95; en-US; rv:1.7.5) Gecko/20041107 Firefox/1.0." Since many different browsers can and have been released from a single Gecko codebase version, this number can form a handy tool to identify which software titles and releases are equivalent in technology and rendering capabilities.

The table below compares the Gecko versions of Netscape (including some of the pseudo-Netscape releases AOL churned out after dissolving the division), Mozilla, Mozilla Firefox, SeaMonkey, Camino, Flock, and K-Meleon.

Gecko codebase	(Year)	Netscape	Mozilla	SeaMonkey	Firefox, Firebird, Phoenix	Camino, Chimera	Flock	K-Meleon
1.9	(2008)				3.0
1.8.1	(2006)	9.0		1.1	2.0	1.5, 1.6	1.0, 1.1	1.1
1.8	(2005)			1.0	1.5	1.0	0.4-0.7	1.0
1.7	(2004)	7.2, 8.x	1.7		0.9, 1.0	0.8		0.9
1.6	(2003)		1.6		0.8
1.5	(2003)		1.5		0.6.1*, 0.7			0.8
1.4	(2003)	7.1	1.4		0.6*
1.3	(2003)		1.3		0.5*
1.2	(2002)		1.2		0.1-0.4*			0.7*
1.1	(2002)		1.1
1.0	(2002)	7.0	1.0			0.4-0.7
0.9.x	(2001)	6.1, 6.2	0.9.x
0.8	(2001)		0.8
0.7	(2001)		0.7
0.6	(2000)	6.0*	0.6

Mozilla Firebird 0.6/0.6.1, Phoenix 0.1 to 0.5, and K-Meleon 0.7 were all based upon alpha or beta versions of the Gecko codebases they correspond to.

Netscape 6.0 and 6.01 were based upon a version of Gecko most equivalent to 0.6, but note the version in the user agent string as "m18," in reference to the previous Mozilla and Gecko codebase release under the early "Milestone" number nomenclature.

The version numbers for various Mozilla application suite releases are the same as those of the Gecko codebases they are based on; i.e., Mozilla 1.7.12 is based on Gecko 1.7.12, and Mozilla 1.0.2 was based on Gecko 1.0.2.