<s>
Firebug	B-Operating_System
is	O
a	O
discontinued	O
free	B-License
and	I-License
open-source	I-License
web	B-Application
browser	I-Application
extension	O
for	O
Mozilla	B-Application
Firefox	I-Application
that	O
facilitated	O
the	O
live	O
debugging	O
,	O
editing	O
,	O
and	O
monitoring	O
of	O
any	O
website	O
's	O
CSS	B-Language
,	O
HTML	B-Language
,	O
DOM	B-General_Concept
,	O
XHR	B-Protocol
,	O
and	O
JavaScript	B-Language
.	O
</s>
<s>
Firebug	B-Operating_System
was	O
licensed	O
under	O
the	O
BSD	B-Operating_System
license	I-Operating_System
and	O
was	O
initially	O
written	O
in	O
January	O
2006	O
by	O
Joe	O
Hewitt	O
,	O
one	O
of	O
the	O
original	O
Firefox	B-Application
creators	O
.	O
</s>
<s>
The	O
Firebug	B-Operating_System
Working	O
Group	O
oversaw	O
the	O
open	O
source	O
development	O
and	O
extension	O
of	O
Firebug	B-Operating_System
.	O
</s>
<s>
It	O
had	O
two	O
major	O
implementations	O
:	O
an	O
extension	O
for	O
Mozilla	B-Application
Firefox	I-Application
and	O
a	O
bookmarklet	B-Language
implementation	O
called	O
Firebug	B-Operating_System
Lite	O
which	O
can	O
be	O
used	O
with	O
Google	B-Application
Chrome	I-Application
.	O
</s>
<s>
In	O
addition	O
to	O
debugging	O
web	O
pages	O
,	O
Firebug	B-Operating_System
was	O
used	O
for	O
web	O
security	O
testing	O
and	O
web	O
page	O
performance	O
analysis	O
.	O
</s>
<s>
Firebug	B-Operating_System
has	O
been	O
deprecated	O
in	O
favor	O
of	O
the	O
integrated	O
developer	O
tools	O
added	O
to	O
Firefox	B-Application
itself	O
,	O
whose	O
functionality	O
has	O
been	O
unified	O
with	O
those	O
of	O
Firebug	B-Operating_System
.	O
</s>
<s>
As	O
Firefox	B-Application
57	O
no	O
longer	O
supports	O
XUL	B-Application
add-ons	B-Operating_System
,	O
Firebug	B-Operating_System
is	O
no	O
longer	O
compatible	O
.	O
</s>
<s>
Firebug	B-Operating_System
2.0	O
introduced	O
many	O
new	O
features	O
to	O
the	O
Firebug	B-Operating_System
extension	O
including	O
JavaScript	B-Language
syntax	O
highlighting	O
,	O
pretty	O
print	O
for	O
minified	O
JavaScript	B-Language
code	O
,	O
and	O
a	O
DOM	B-General_Concept
Event	O
Inspector	O
to	O
handle	O
all	O
event	O
handlers	O
on	O
a	O
web	O
page	O
.	O
</s>
<s>
Additionally	O
,	O
users	O
can	O
search	O
for	O
page	O
elements	O
using	O
CSS	B-Language
selectors	O
in	O
the	O
search	O
bar	O
.	O
</s>
<s>
The	O
debugging	O
tool	O
now	O
allows	O
users	O
to	O
inspect	O
JavaScript	B-Language
expressions	O
as	O
they	O
are	O
evaluated	O
.	O
</s>
<s>
Moreover	O
,	O
users	O
can	O
inspect	O
values	O
returned	O
from	O
JavaScript	B-Language
functions	O
.	O
</s>
<s>
It	O
also	O
adds	O
the	O
ability	O
to	O
create	O
new	O
HTML	B-Language
attributes	O
for	O
existing	O
HTML	B-Language
elements	O
.	O
</s>
<s>
On	O
November	O
10	O
,	O
2014	O
,	O
Firebug	B-Operating_System
3.0	O
was	O
announced	O
and	O
an	O
alpha	O
was	O
made	O
available	O
to	O
the	O
public	O
.	O
</s>
<s>
Firebug	B-Operating_System
makes	O
changes	O
immediately	O
and	O
gives	O
constant	O
feedback	O
to	O
the	O
user	O
.	O
</s>
<s>
All	O
editors	O
in	O
Firebug	B-Operating_System
support	O
autocomplete	O
.	O
</s>
<s>
The	O
Firebug	B-Operating_System
command	O
line	O
accepts	O
commands	O
written	O
in	O
JavaScript	B-Language
.	O
</s>
<s>
The	O
Firebug	B-Operating_System
application	O
contains	O
multiple	O
windows	O
,	O
splitting	O
related	O
features	O
to	O
a	O
common	O
window	O
.	O
</s>
<s>
Firebug	B-Operating_System
also	O
allows	O
users	O
to	O
view	O
the	O
download	O
time	O
for	O
individual	O
files	O
.	O
</s>
<s>
It	O
separates	O
different	O
types	O
of	O
objects	O
,	O
such	O
as	O
JavaScript	B-Language
files	O
and	O
images	O
,	O
and	O
can	O
determined	O
which	O
files	O
are	O
loaded	O
from	O
a	O
browser	B-Application
's	O
cache	O
.	O
</s>
<s>
Firebug	B-Operating_System
also	O
features	O
the	O
ability	O
to	O
examine	O
HTTP	O
headers	O
and	O
time	O
stamps	O
relative	O
to	O
when	O
an	O
HTTP	O
request	O
is	O
made	O
.	O
</s>
<s>
Its	O
net	O
panel	O
can	O
monitor	O
URLs	O
that	O
the	O
browser	B-Application
requests	O
,	O
such	O
as	O
external	O
CSS	B-Language
,	O
JavaScript	B-Language
,	O
and	O
image	O
files	O
.	O
</s>
<s>
The	O
HTML	B-Language
and	O
CSS	B-Language
tools	O
allow	O
for	O
the	O
inspection	O
and	O
editing	O
of	O
HTML	B-Language
and	O
CSS	B-Language
elements	O
on	O
a	O
web	O
page	O
.	O
</s>
<s>
Later	O
versions	O
of	O
Firebug	B-Operating_System
allow	O
users	O
to	O
see	O
live	O
changes	O
to	O
the	O
CSS	B-Language
.	O
</s>
<s>
Visualization	O
of	O
CSS	B-Language
elements	O
is	O
shown	O
while	O
inspecting	O
HTML	B-Language
elements	O
.	O
</s>
<s>
The	O
Firebug	B-Operating_System
layout	O
tab	O
is	O
used	O
to	O
display	O
and	O
manipulate	O
CSS	B-Language
property	O
values	O
.	O
</s>
<s>
Furthermore	O
,	O
users	O
can	O
click	O
on	O
any	O
visible	O
HTML	B-Language
elements	O
on	O
a	O
web	O
page	O
to	O
access	O
its	O
CSS	B-Language
property	O
values	O
.	O
</s>
<s>
Firebug	B-Operating_System
's	O
script	O
tab	O
enables	O
users	O
to	O
set	O
breakpoints	O
and	O
step	O
through	O
lines	O
of	O
code	O
.	O
</s>
<s>
Additionally	O
,	O
Firebug	B-Operating_System
can	O
navigate	O
directly	O
to	O
a	O
line	O
of	O
JavaScript	B-Language
code	O
,	O
watch	O
expressions	O
,	O
call	O
stacks	O
,	O
and	O
launch	O
the	O
debugger	O
in	O
the	O
event	O
an	O
error	O
occurs	O
during	O
execution	O
.	O
</s>
<s>
Firebug	B-Operating_System
can	O
also	O
log	O
errors	O
.	O
</s>
<s>
Logging	O
uses	O
a	O
Firebug	B-Operating_System
JavaScript	B-Language
API	O
.	O
</s>
<s>
Firebug	B-Operating_System
's	O
JavaScript	B-Language
panel	O
can	O
log	O
errors	O
,	O
profile	O
function	O
calls	O
,	O
and	O
enable	O
the	O
developer	O
to	O
run	O
arbitrary	O
JavaScript	B-Language
.	O
</s>
<s>
Firebug	B-Operating_System
allows	O
users	O
to	O
run	O
JavaScript	B-Language
code	O
through	O
the	O
command	O
line	O
and	O
allows	O
the	O
user	O
to	O
log	O
errors	O
that	O
occur	O
in	O
the	O
JavaScript	B-Language
,	O
CSS	B-Language
,	O
and	O
XML	O
.	O
</s>
<s>
Firebug	B-Operating_System
provides	O
a	O
separate	O
text	O
editor	O
to	O
modify	O
the	O
JavaScript	B-Language
and	O
see	O
immediate	O
results	O
on	O
the	O
user	O
's	O
browser	B-Application
.	O
</s>
<s>
As	O
provided	O
in	O
an	O
update	O
,	O
the	O
JavaScript	B-Language
command	O
line	O
features	O
an	O
autocomplete	O
function	O
.	O
</s>
<s>
Firebug	B-Operating_System
requires	O
a	O
user	O
to	O
refresh	O
a	O
web	O
page	O
in	O
the	O
event	O
of	O
a	O
crash	O
.	O
</s>
<s>
Many	O
extensions	O
have	O
been	O
made	O
to	O
enhance	O
Firebug	B-Operating_System
.	O
</s>
<s>
Since	O
Firebug	B-Operating_System
is	O
open	O
source	O
,	O
users	O
can	O
contribute	O
their	O
own	O
extensions	O
to	O
the	O
Firebug	B-Operating_System
community	O
.	O
</s>
