<s>
Firefox	B-Operating_System
Sync	I-Operating_System
,	O
originally	O
branded	O
Mozilla	B-Operating_System
Weave	I-Operating_System
,	O
is	O
a	O
browser	B-Application
synchronization	I-Application
feature	O
for	O
Firefox	B-Application
web	I-Application
browsers	I-Application
.	O
</s>
<s>
It	O
allows	O
users	O
to	O
partially	O
synchronize	O
bookmarks	O
,	O
browsing	O
history	O
,	O
preferences	O
,	O
passwords	O
,	O
filled	O
forms	O
,	O
add-ons	B-Operating_System
,	O
and	O
the	O
last	O
25	O
opened	O
tabs	O
across	O
multiple	O
computers	O
.	O
</s>
<s>
The	O
feature	O
is	O
now	O
included	O
in	O
Firefox	B-Application
and	O
it	O
's	O
being	O
implemented	O
in	O
Thunderbird	B-Application
.	O
</s>
<s>
It	O
keeps	O
user	O
data	O
on	O
Mozilla	B-Operating_System
servers	O
,	O
but	O
according	O
to	O
Mozilla	B-Operating_System
the	O
data	O
is	O
encrypted	O
in	O
such	O
a	O
way	O
that	O
no	O
third	O
party	O
,	O
not	O
even	O
Mozilla	B-Operating_System
,	O
can	O
access	O
user	O
information	O
.	O
</s>
<s>
It	O
is	O
also	O
possible	O
for	O
the	O
user	O
to	O
host	O
their	O
own	O
Firefox	B-Operating_System
Sync	I-Operating_System
servers	O
,	O
or	O
indeed	O
,	O
for	O
any	O
entity	O
to	O
do	O
so	O
.	O
</s>
<s>
Firefox	B-Operating_System
Sync	I-Operating_System
was	O
originally	O
an	O
add-on	B-Operating_System
for	O
Mozilla	B-Application
Firefox	I-Application
3.x	O
and	O
SeaMonkey	B-Language
2.0	O
,	O
but	O
it	O
has	O
been	O
a	O
built-in	O
feature	O
since	O
Firefox	B-Application
4.0	O
and	O
SeaMonkey	B-Language
2.1	O
.	O
</s>
<s>
Firefox	B-Operating_System
Sync	I-Operating_System
is	O
built	O
on	O
top	O
of	O
Firefox	B-Application
Accounts	O
as	O
of	O
Firefox	B-Application
29	O
,	O
and	O
therefore	O
Firefox	B-Application
29	O
and	O
later	O
cannot	O
sync	O
with	O
Firefox	B-Application
28	O
and	O
earlier	O
.	O
</s>
<s>
Firefox	B-Application
Home	O
was	O
a	O
companion	O
application	O
for	O
the	O
iPhone	B-Device
and	O
iPod	B-Device
Touch	I-Device
based	O
on	O
the	O
Firefox	B-Operating_System
Sync	I-Operating_System
technology	O
.	O
</s>
<s>
Firefox	B-Application
Home	O
was	O
not	O
considered	O
a	O
web	O
browser	O
,	O
as	O
it	O
would	O
launch	O
pages	O
in	O
either	O
an	O
embedded	O
viewer	O
or	O
by	O
switching	O
to	O
the	O
Safari	O
app	O
.	O
</s>
<s>
In	O
December	O
2014	O
,	O
Mozilla	B-Operating_System
announced	O
Firefox	B-Application
for	I-Application
iOS	I-Application
,	O
a	O
version	O
of	O
the	O
Firefox	B-Application
browser	I-Application
for	O
iOS	B-Application
,	O
which	O
includes	O
Firefox	B-Operating_System
Sync	I-Operating_System
support	O
for	O
syncing	O
Firefox	B-Application
's	O
browsing	O
history	O
,	O
bookmarks	O
,	O
and	O
recent	O
tabs	O
.	O
</s>
<s>
Mozilla	B-Operating_System
also	O
offers	O
a	O
synchronization	O
server	O
application	O
for	O
use	O
with	O
Firefox	B-Operating_System
Sync	I-Operating_System
,	O
for	O
users	O
and	O
businesses	O
that	O
prefer	O
to	O
host	O
their	O
own	O
synchronization	O
data	O
.	O
</s>
