<s>
Gecko	O
is	O
a	O
browser	B-Protocol
engine	I-Protocol
developed	O
by	O
Mozilla	B-Operating_System
.	O
</s>
<s>
It	O
is	O
used	O
in	O
the	O
Firefox	B-Application
browser	I-Application
,	O
the	O
Thunderbird	B-Application
email	B-Protocol
client	I-Protocol
,	O
and	O
many	O
other	O
projects	O
.	O
</s>
<s>
Gecko	O
is	O
designed	O
to	O
support	O
open	O
Internet	O
standards	O
,	O
and	O
is	O
used	O
by	O
different	O
applications	O
to	O
display	O
web	O
pages	O
and	O
,	O
in	O
some	O
cases	O
,	O
an	O
application	O
's	O
user	B-Application
interface	I-Application
itself	O
(	O
by	O
rendering	O
XUL	B-Application
)	O
.	O
</s>
<s>
Gecko	O
offers	O
a	O
rich	O
programming	O
API	B-Application
that	O
makes	O
it	O
suitable	O
for	O
a	O
wide	O
variety	O
of	O
roles	O
in	O
Internet-enabled	O
applications	O
,	O
such	O
as	O
web	B-Application
browsers	I-Application
,	O
content	O
presentation	O
,	O
and	O
client/server	B-Operating_System
.	O
</s>
<s>
Gecko	O
is	O
written	O
in	O
C++	B-Language
and	O
JavaScript	B-Language
,	O
and	O
,	O
since	O
2016	O
,	O
additionally	O
in	O
Rust	B-Application
.	O
</s>
<s>
It	O
is	O
free	B-License
and	I-License
open-source	I-License
software	I-License
subject	O
to	O
the	O
terms	O
of	O
the	O
Mozilla	B-License
Public	I-License
License	I-License
version	O
2	O
.	O
</s>
<s>
Mozilla	B-Operating_System
officially	O
supports	O
its	O
use	O
on	O
Android	B-Application
,	O
Linux	B-Application
,	O
macOS	B-Application
,	O
and	O
Windows	O
.	O
</s>
<s>
Development	O
of	O
the	O
layout	B-Protocol
engine	I-Protocol
now	O
known	O
as	O
Gecko	O
began	O
at	O
Netscape	O
in	O
1997	O
,	O
following	O
the	O
company	O
's	O
purchase	O
of	O
DigitalStyle	O
.	O
</s>
<s>
The	O
existing	O
Netscape	O
rendering	O
engine	B-Protocol
,	O
originally	O
written	O
for	O
Netscape	B-Protocol
Navigator	I-Protocol
1.0	O
and	O
upgraded	O
through	O
the	O
years	O
,	O
was	O
slow	O
,	O
did	O
not	O
comply	O
well	O
with	O
W3C	O
standards	O
,	O
had	O
limited	O
support	O
for	O
dynamic	B-General_Concept
HTML	I-General_Concept
and	O
lacked	O
features	O
such	O
as	O
incremental	O
reflow	O
(	O
when	O
the	O
layout	B-Protocol
engine	I-Protocol
rearranges	O
elements	O
on	O
the	O
screen	O
as	O
new	O
data	O
is	O
downloaded	O
and	O
added	O
to	O
the	O
page	O
)	O
.	O
</s>
<s>
The	O
new	O
layout	B-Protocol
engine	I-Protocol
was	O
developed	O
in	O
parallel	O
with	O
the	O
old	O
,	O
with	O
the	O
intention	O
being	O
to	O
integrate	O
it	O
into	O
Netscape	B-Protocol
Communicator	I-Protocol
when	O
it	O
was	O
mature	O
and	O
stable	O
.	O
</s>
<s>
At	O
least	O
one	O
more	O
major	O
revision	O
of	O
Netscape	O
was	O
expected	O
to	O
be	O
released	O
with	O
the	O
old	O
layout	B-Protocol
engine	I-Protocol
before	O
the	O
switch	O
.	O
</s>
<s>
After	O
the	O
launch	O
of	O
the	O
Mozilla	B-Operating_System
project	I-Operating_System
in	O
early	O
1998	O
,	O
the	O
new	O
layout	B-Protocol
engine	I-Protocol
code	O
was	O
released	O
under	O
an	O
open-source	O
license	O
.	O
</s>
<s>
While	O
Mozilla	B-Operating_System
Organization	I-Operating_System
(	O
the	O
forerunner	O
of	O
the	B-Operating_System
Mozilla	I-Operating_System
Foundation	I-Operating_System
)	O
initially	O
continued	O
to	O
use	O
the	O
NGLayout	O
name	O
(	O
Gecko	O
was	O
a	O
Netscape	O
trademark	O
)	O
,	O
eventually	O
the	O
Gecko	O
branding	O
won	O
out	O
.	O
</s>
<s>
In	O
October	O
1998	O
,	O
Netscape	O
announced	O
that	O
its	O
next	O
browser	B-Application
would	O
use	O
Gecko	O
(	O
which	O
was	O
still	O
called	O
NGLayout	O
at	O
the	O
time	O
)	O
rather	O
than	O
the	O
old	O
layout	B-Protocol
engine	I-Protocol
,	O
requiring	O
large	O
parts	O
of	O
the	O
application	O
to	O
be	O
rewritten	O
.	O
</s>
<s>
It	O
also	O
meant	O
that	O
most	O
of	O
the	O
work	O
done	O
for	O
Netscape	B-Protocol
Communicator	I-Protocol
5.0	O
(	O
including	O
development	O
on	O
the	O
Mariner	B-Application
improvements	O
to	O
the	O
old	O
layout	B-Protocol
engine	I-Protocol
)	O
had	O
to	O
be	O
abandoned	O
.	O
</s>
<s>
Netscape	B-Protocol
6	I-Protocol
,	O
the	O
first	O
Netscape	O
release	O
to	O
incorporate	O
Gecko	O
,	O
was	O
released	O
in	O
November	O
2000	O
(	O
the	O
name	O
Netscape	O
5	O
was	O
never	O
used	O
)	O
.	O
</s>
<s>
America	O
Online	O
,	O
by	O
this	O
time	O
Netscape	O
's	O
parent	O
company	O
,	O
eventually	O
adopted	O
it	O
for	O
use	O
in	O
CompuServe	O
7.0	O
and	O
AOL	O
for	O
Mac	B-Application
OS	I-Application
X	O
(	O
these	O
products	O
had	O
previously	O
embedded	O
Internet	B-Application
Explorer	I-Application
)	O
.	O
</s>
<s>
However	O
,	O
with	O
the	O
exception	O
of	O
a	O
few	O
betas	O
,	O
Gecko	O
was	O
never	O
used	O
in	O
the	O
main	O
Microsoft	B-Application
Windows	I-Application
AOL	O
client	O
.	O
</s>
<s>
On	O
July	O
15	O
,	O
2003	O
,	O
AOL	O
laid	O
off	O
the	O
remaining	O
Gecko	O
developers	O
and	O
the	B-Operating_System
Mozilla	I-Operating_System
Foundation	I-Operating_System
(	O
formed	O
on	O
the	O
same	O
day	O
)	O
became	O
the	O
main	O
steward	O
of	O
Gecko	O
development	O
.	O
</s>
<s>
Today	O
,	O
Gecko	O
is	O
developed	O
by	O
employees	O
of	O
the	O
Mozilla	B-Operating_System
Corporation	O
,	O
employees	O
of	O
companies	O
that	O
contribute	O
to	O
the	O
Mozilla	B-Operating_System
project	I-Operating_System
,	O
and	O
volunteers	O
.	O
</s>
<s>
In	O
October	O
2016	O
,	O
Mozilla	B-Operating_System
announced	O
Quantum	O
,	O
an	O
ongoing	O
project	O
encompassing	O
several	O
software	O
development	O
efforts	O
to	O
"	O
build	O
the	O
next-generation	O
web	B-Protocol
engine	I-Protocol
for	O
Firefox	B-Application
users	O
"	O
.	O
</s>
<s>
It	O
included	O
numerous	O
improvements	O
to	O
Gecko	O
,	O
taken	O
from	O
the	O
experimental	O
Servo	B-Application
project	I-Application
.	O
</s>
<s>
Firefox	B-Application
57	O
,	O
also	O
known	O
as	O
"	O
Firefox	B-Application
Quantum	O
"	O
,	O
first	O
shipping	O
in	O
November	O
2017	O
,	O
is	O
the	O
initial	O
version	O
with	O
major	O
components	O
from	O
the	O
Quantum/Servo	O
projects	O
enabled	O
.	O
</s>
<s>
These	O
include	O
increased	O
performance	O
in	O
the	O
CSS	B-Language
and	O
GPU	B-Architecture
rendering	O
components	O
.	O
</s>
<s>
Additional	O
components	O
will	O
be	O
merged	O
from	O
Servo	B-Application
to	O
Gecko	O
incrementally	O
in	O
future	O
versions	O
.	O
</s>
<s>
In	O
September	O
2018	O
,	O
Mozilla	B-Operating_System
announced	O
GeckoView	O
,	O
the	O
foundation	O
of	O
Mozilla	B-Operating_System
's	O
next	O
generation	O
of	O
mobile	O
products	O
based	O
on	O
a	O
software	O
library	O
that	O
makes	O
Gecko	O
reusable	O
for	O
Android	B-Application
,	O
encompassing	O
newer	O
software	O
development	O
efforts	O
to	O
"	O
decouple	O
the	O
engine	B-Protocol
itself	O
from	O
its	O
user	B-Application
interface	I-Application
,	O
and	O
made	O
it	O
easy	O
to	O
embed	O
in	O
other	O
applications	O
"	O
.	O
</s>
<s>
Firefox	B-Application
Focus	O
7.0	O
,	O
shipped	O
in	O
the	O
same	O
month	O
,	O
is	O
the	O
initial	O
version	O
introduced	O
GeckoView	O
,	O
with	O
increased	O
performance	O
in	O
median	O
page	O
loading	O
.	O
</s>
<s>
Firefox	B-Application
Reality	O
was	O
also	O
built	O
with	O
GeckoView	O
.	O
</s>
<s>
In	O
June	O
2019	O
,	O
Mozilla	B-Operating_System
announced	O
Firefox	B-Application
Preview	O
as	O
an	O
ongoing	O
project	O
that	O
focuses	O
on	O
building	O
an	O
Android	B-Application
web	B-Application
browser	I-Application
with	O
GeckoView	O
.	O
</s>
<s>
Firefox	B-Application
for	I-Application
Android	I-Application
79	O
,	O
also	O
known	O
as	O
"	O
Firefox	B-Application
Daylight	I-Application
"	O
,	O
first	O
shipping	O
in	O
August	O
2020	O
,	O
is	O
the	O
first	O
stable	O
release	O
of	O
that	O
with	O
major	O
components	O
powered	O
by	O
GeckoView	O
engine	B-Protocol
.	O
</s>
<s>
Gecko	O
also	O
supports	O
SVG	B-Application
.	O
</s>
<s>
In	O
order	O
to	O
support	O
web	O
pages	O
designed	O
for	O
legacy	O
versions	O
of	O
Netscape	O
and	O
Internet	B-Application
Explorer	I-Application
,	O
Gecko	O
supports	O
DOCTYPE	O
switching	O
.	O
</s>
<s>
Documents	O
that	O
have	O
no	O
DOCTYPE	O
or	O
an	O
older	O
DOCTYPE	O
are	O
rendered	O
in	O
quirks	B-General_Concept
mode	I-General_Concept
,	O
which	O
emulates	O
some	O
of	O
the	O
non-standard	O
oddities	O
of	O
Netscape	B-Protocol
Communicator	I-Protocol
4.x	O
;	O
however	O
,	O
some	O
of	O
the	O
4.x	O
features	O
(	O
such	O
as	O
layers	O
)	O
are	O
not	O
supported	O
.	O
</s>
<s>
Gecko	O
also	O
has	O
limited	O
support	O
for	O
some	O
non-standard	O
Internet	B-Application
Explorer	I-Application
features	O
,	O
such	O
as	O
the	O
marquee	B-General_Concept
element	I-General_Concept
and	O
the	O
document.all	O
property	O
(	O
though	O
pages	O
explicitly	O
testing	O
for	O
document.all	O
will	O
be	O
told	O
it	O
is	O
not	O
supported	O
)	O
.	O
</s>
<s>
Gecko	O
is	O
primarily	O
used	O
in	O
web	B-Application
browsers	I-Application
,	O
the	O
earliest	O
being	O
Netscape	B-Protocol
6	I-Protocol
and	O
Mozilla	B-Language
Suite	I-Language
(	O
later	O
renamed	O
SeaMonkey	B-Language
)	O
.	O
</s>
<s>
It	O
is	O
also	O
used	O
in	O
other	O
Mozilla	B-Operating_System
web	B-Application
browser	I-Application
derivatives	O
such	O
as	O
Firefox	B-Application
and	O
Firefox	B-Application
for	I-Application
mobile	I-Application
and	O
the	O
implementation	O
of	O
the	O
Internet	O
Explorer-clone	O
that	O
is	O
part	O
of	O
Wine	B-Application
.	O
</s>
<s>
Mozilla	B-Operating_System
also	O
uses	O
it	O
in	O
their	O
Thunderbird	B-Application
email-client	I-Application
.	O
</s>
<s>
Other	O
web	B-Application
browsers	I-Application
using	O
Gecko	O
include	O
GNU	B-Application
IceCat	I-Application
,	O
Waterfox	B-Language
,	O
K-Meleon	B-Protocol
,	O
Lunascape	B-Operating_System
,	O
Portable	B-Operating_System
Firefox	I-Operating_System
,	O
Conkeror	B-Protocol
,	O
Classilla	B-Protocol
,	O
TenFourFox	B-Operating_System
.	O
</s>
<s>
Gecko	O
is	O
also	O
used	O
by	O
Sugar	B-Language
for	O
the	O
OLPC	B-Application
XO-1	I-Application
computer	O
.	O
</s>
<s>
Gecko	O
is	O
used	O
as	O
a	O
complete	O
implementation	O
of	O
the	O
XUL	B-Application
(	O
XML	B-Application
User	I-Application
Interface	I-Application
Language	I-Application
)	O
.	O
</s>
<s>
Gecko	O
currently	O
defines	O
the	O
XUL	B-Application
specification	O
.	O
</s>
<s>
Products	O
that	O
formerly	O
used	O
Gecko	O
include	O
Pale	B-Protocol
Moon	I-Protocol
(	O
now	O
using	O
Goanna	B-Language
)	O
,	O
Epiphany	B-Language
(	O
now	O
known	O
as	O
GNOME	B-Language
Web	I-Language
and	O
using	O
WebKitGTK	O
)	O
,	O
and	O
GNOME	B-Language
DevHelp	I-Language
(	O
now	O
using	O
WebKitGTK	O
.	O
)	O
</s>
<s>
Discontinued	O
products	O
that	O
used	O
Gecko	O
include	O
Swiftfox	B-Protocol
,	O
Flock	B-Protocol
,	O
Galeon	B-Language
,	O
Camino	B-Language
,	O
Minimo	B-Application
,	O
Beonex	B-Protocol
Communicator	I-Protocol
,	O
Kazehakase	B-Language
,	O
Songbird	B-Application
,	O
Sunbird	O
(	O
calendar	O
)	O
,	O
MicroB	B-Protocol
,	O
Nightingale	B-Language
,	O
Instantbird	B-Protocol
,	O
and	O
Picasa	B-Application
for	O
Linux	B-Application
.	O
</s>
<s>
On	O
Windows	O
and	O
other	O
platforms	O
,	O
Gecko	O
depends	O
on	O
proprietary	O
compilers	B-Language
.	O
</s>
<s>
Thus	O
,	O
FOSS	B-License
distributions	O
of	O
Linux	B-Application
cannot	O
include	O
the	O
Gecko	O
package	O
used	O
in	O
the	O
Windows	O
compatibility	O
layer	O
Wine	B-Application
.	O
</s>
<s>
After	O
Gecko	O
2.0	O
,	O
the	O
version	O
number	O
was	O
bumped	O
to	O
5.0	O
to	O
match	O
Firefox	B-Application
5	O
,	O
and	O
from	O
then	O
on	O
has	O
been	O
kept	O
in	O
sync	O
with	O
the	O
major	O
version	O
number	O
for	O
both	O
Firefox	B-Application
and	O
Thunderbird	B-Application
,	O
to	O
reflect	O
the	O
fact	O
that	O
it	O
is	O
no	O
longer	O
a	O
separate	O
component	O
.	O
</s>
<s>
Thus	O
in	O
2001	O
Apple	O
chose	O
to	O
fork	O
KHTML	B-Language
,	O
not	O
Gecko	O
,	O
to	O
create	O
the	O
WebKit	B-Language
engine	B-Protocol
for	O
its	O
Safari	B-Application
browser	I-Application
.	O
</s>
<s>
However	O
,	O
by	O
2008	O
Mozilla	B-Operating_System
had	O
addressed	O
some	O
of	O
the	O
bloat	O
problems	O
,	O
resulting	O
in	O
big	O
performance	O
improvements	O
for	O
Gecko	O
.	O
</s>
<s>
Quantum	O
is	O
a	O
Mozilla	B-Operating_System
project	I-Operating_System
encompassing	O
several	O
software	O
development	O
efforts	O
to	O
"	O
build	O
the	O
next-generation	O
web	B-Protocol
engine	I-Protocol
for	O
Firefox	B-Application
users	O
"	O
.	O
</s>
<s>
It	O
includes	O
numerous	O
improvements	O
to	O
Gecko	O
,	O
largely	O
incorporated	O
from	O
the	O
experimental	O
Servo	B-Application
project	I-Application
.	O
</s>
<s>
Quantum	O
also	O
includes	O
refinements	O
to	O
the	O
user	B-Application
interface	I-Application
and	O
interactions	O
.	O
</s>
<s>
Firefox	B-Application
57	O
,	O
released	O
in	O
November	O
2017	O
,	O
is	O
the	O
initial	O
version	O
with	O
a	O
Servo	B-Application
component	O
enabled	O
.	O
</s>
<s>
Mozilla	B-Operating_System
dubs	O
this	O
and	O
several	O
planned	O
future	O
releases	O
"	O
Firefox	B-Application
Quantum	O
"	O
.	O
</s>
<s>
In	O
2012	O
,	O
Mozilla	B-Operating_System
began	O
the	O
experimental	O
Servo	B-Application
project	I-Application
,	O
which	O
is	O
an	O
engine	B-Protocol
designed	O
from	O
scratch	O
with	O
the	O
goals	O
of	O
improving	O
concurrency	B-Operating_System
and	I-Operating_System
parallelism	I-Operating_System
while	O
also	O
reducing	O
memory	B-Application
safety	I-Application
vulnerabilities	O
.	O
</s>
<s>
Servo	B-Application
is	O
written	O
in	O
the	O
Rust	B-Application
programming	I-Application
language	I-Application
,	O
also	O
created	O
by	O
Mozilla	B-Operating_System
,	O
which	O
is	O
designed	O
to	O
generate	O
compiled	B-Language
code	O
with	O
better	O
memory	B-Application
safety	I-Application
,	O
concurrency	O
,	O
and	O
parallelism	B-Operating_System
than	O
compiled	B-Language
C++	B-Language
code	I-Language
.	O
</s>
<s>
As	O
of	O
April	O
2016	O
,	O
Servo	B-Application
needed	O
at	O
least	O
several	O
years	O
of	O
development	O
to	O
become	O
a	O
full-featured	O
browser	B-Protocol
engine	I-Protocol
,	O
hence	O
the	O
decision	O
to	O
start	O
the	O
Quantum	O
project	O
to	O
bring	O
stable	O
portions	O
of	O
Servo	B-Application
into	O
Firefox	B-Application
.	O
</s>
<s>
Mozilla	B-Operating_System
laid	O
off	O
all	O
Servo	B-Application
developers	O
in	O
August	O
2020	O
.	O
</s>
<s>
CSS	B-Language
:	O
Servo	B-Application
's	O
parallel	O
style	B-Language
sheet	I-Language
system	O
integrated	O
into	O
Gecko	O
.	O
</s>
<s>
Benchmarks	O
suggest	O
that	O
performance	O
scales	O
linearly	O
with	O
number	O
of	O
CPU	B-Device
cores	O
.	O
</s>
<s>
This	O
was	O
released	O
in	O
Firefox	B-Application
57	O
.	O
</s>
<s>
Render	O
:	O
Servo	B-Application
's	O
rendering	O
architecture	O
,	O
called	O
WebRender	O
,	O
integrated	O
into	O
Gecko	O
.	O
</s>
<s>
WebRender	O
replaces	O
the	O
immediate	O
mode	O
drawing	O
model	O
with	O
a	O
retained	O
mode	O
model	O
that	O
is	O
more	O
easily	O
accelerated	O
by	O
the	O
GPU	B-Architecture
by	O
taking	O
advantage	O
of	O
CSS/DOM	O
'	O
s	O
similarity	O
to	O
a	O
scene	B-Data_Structure
graph	I-Data_Structure
.	O
</s>
<s>
Mozilla	B-Operating_System
began	O
enabling	O
the	O
new	O
renderer	O
for	O
select	O
hardware/OS	O
combinations	O
in	O
Firefox	B-Application
67	O
.	O
</s>
<s>
Compositor	O
:	O
Gecko	O
's	O
existing	O
compositor	O
moved	O
to	O
its	O
own	O
process	O
,	O
isolating	O
browser	B-Application
tabs	O
from	O
graphics	O
driver	O
related	O
crashes	O
.	O
</s>
<s>
Since	O
compositor	O
crashes	O
will	O
not	O
bring	O
down	O
the	O
browser	B-Application
content	O
process	O
,	O
the	O
compositor	O
process	O
can	O
be	O
restarted	O
transparently	O
without	O
losing	O
user	O
data	O
.	O
</s>
<s>
This	O
was	O
released	O
in	O
Firefox	B-Application
53	O
.	O
</s>
<s>
DOM	B-General_Concept
:	O
Loosely	O
inspired	O
by	O
Servo	B-Application
's	O
Constellation	O
architecture	O
and	O
Opera	B-Application
's	O
Presto	B-Application
engine	B-Protocol
,	O
Quantum	O
DOM	B-General_Concept
uses	O
cooperatively	O
scheduled	O
threads	O
within	O
the	B-General_Concept
DOM	I-General_Concept
to	O
increase	O
responsiveness	O
without	O
increasing	O
the	O
number	O
of	O
processes	O
and	O
,	O
thus	O
,	O
memory	O
usage	O
.	O
</s>
<s>
The	O
core	O
of	O
this	O
shipped	O
in	O
Firefox	B-Application
57	O
.	O
</s>
<s>
Focused	O
on	O
real	O
user	O
performance	O
improvements	O
on	O
major	O
webapps	B-Application
,	O
primarily	O
G	B-Application
Suite	I-Application
(	O
now	O
called	O
Google	B-Application
Workspace	I-Application
)	O
and	O
Facebook	B-Application
.	I-Application
</s>
<s>
This	O
work	O
completed	O
and	O
shipped	O
for	O
Firefox	B-Application
57	O
.	O
</s>
<s>
Photon	O
:	O
A	O
UI	B-Application
refresh	O
of	O
the	O
entire	O
application	O
,	O
with	O
a	O
strong	O
focus	O
on	O
improving	O
UI	B-Application
performance	O
.	O
</s>
<s>
This	O
was	O
released	O
in	O
Firefox	B-Application
57	O
.	O
</s>
<s>
Network	O
:	O
Improve	O
the	O
performance	O
of	O
Necko	B-Application
,	O
Gecko	O
's	O
networking	O
layer	O
,	O
by	O
moving	O
more	O
network	O
activity	O
off	O
the	O
main	O
thread	O
,	O
context	O
dependent	O
prioritization	O
of	O
networking	O
streams	O
,	O
and	O
racing	O
the	O
cache	O
layer	O
with	O
the	O
network	O
.	O
</s>
<s>
This	O
feature	O
was	O
released	O
in	O
Firefox	B-Application
59	O
.	O
</s>
<s>
The	O
Mozilla	B-Operating_System
Azure	O
project	O
is	O
a	O
stateless	O
low-level	O
graphics	O
abstraction	O
API	B-Application
used	O
in	O
Firefox	B-Application
.	O
</s>
<s>
Firefox	B-Application
began	O
using	O
Azure	O
instead	O
of	O
Cairo	B-Language
in	O
2012	O
.	O
</s>
<s>
It	O
is	O
written	O
in	O
C++	B-Language
and	O
used	O
by	O
Servo	B-Application
.	O
</s>
