<s>
Link	B-Protocol
prefetching	I-Protocol
allows	O
web	O
browsers	O
to	O
pre-load	O
resources	O
.	O
</s>
<s>
Prefetching	O
was	O
first	O
introduced	O
in	O
HTML5	B-Application
.	O
</s>
<s>
Resources	O
which	O
can	O
be	O
prefetched	O
include	O
:	O
JavaScript	B-Language
,	O
CSS	B-Language
,	O
image	O
,	O
audio	O
,	O
video	O
,	O
and	O
web	O
fonts	O
.	O
</s>
<s>
DNS	B-Protocol
names	I-Protocol
and	O
TCP	B-Protocol
connections	O
can	O
also	O
be	O
hinted	O
for	O
prefetching	O
.	O
</s>
<s>
There	O
are	O
two	O
W3C	O
standards	O
covering	O
prefetching	O
for	O
HTML5	B-Application
:	O
</s>
<s>
Common	O
hints	O
include	O
JavaScript	B-Language
,	O
CSS	B-Language
,	O
images	O
and	O
web	O
fonts	O
.	O
</s>
<s>
Common	O
hints	O
include	O
DNS	B-Protocol
queries	I-Protocol
,	O
opening	O
TCP	B-Protocol
connections	O
,	O
and	O
page	O
pre-rendering	O
.	O
</s>
<s>
HTML5	B-Application
methods	O
for	O
prefetch	O
hints	O
:	O
</s>
<s>
Link	O
for	O
HTTP	B-Protocol
headers	I-Protocol
:	O
Example	O
below	O
.	O
</s>
<s>
iCab	B-Operating_System
,	O
Mozilla	B-Language
Application	I-Language
Suite	I-Language
,	O
and	O
WebTV	B-Device
are	O
the	O
first	O
referenced	O
browsers	O
to	O
support	O
link	B-Protocol
prefetching	I-Protocol
.	O
</s>
<s>
Mozilla	B-Application
Firefox	I-Application
supports	O
DNS	B-Protocol
prefetching	I-Protocol
,	O
as	O
of	O
version	O
3.5	O
.	O
</s>
<s>
Google	B-Application
Chrome	I-Application
supports	O
prefetching	O
of	O
linked	O
web	O
content	O
by	O
"	O
prerendering	O
"	O
,	O
as	O
of	O
version11	O
.	O
</s>
<s>
Internet	B-Application
Explorer	I-Application
supports	O
prefetching	O
of	O
IP	O
addresses	O
by	O
"	O
DNS	B-Protocol
prefetching	I-Protocol
"	O
,	O
as	O
of	O
version9	O
.	O
</s>
<s>
As	O
of	O
version	O
11	O
,	O
Internet	B-Application
Explorer	I-Application
supports	O
the	O
following	O
set	O
of	O
features	O
to	O
expand	O
its	O
prefetching	O
capabilities	O
:	O
"	O
prerender	O
"	O
,	O
"	O
dns-prefetch	O
"	O
and	O
"	O
lazyload	O
"	O
(	O
images	O
only	O
)	O
.	O
</s>
<s>
Google	B-Application
is	O
the	O
most	O
well-known	O
website	O
that	O
takes	O
advantage	O
of	O
this	O
feature	O
so	O
as	O
to	O
improve	O
the	O
user	O
experience	O
.	O
</s>
<s>
Specifically	O
,	O
Google	B-Application
implemented	O
"	O
Google	B-Application
Instant	O
Pages	O
"	O
in	O
August	O
2011	O
which	O
takes	O
advantage	O
of	O
the	O
aforementioned	O
feature	O
,	O
predictive	O
search	O
completion	O
,	O
and	O
preloading	O
search	O
results	O
as	O
the	O
user	O
types	O
in	O
order	O
to	O
improve	O
the	O
performance	O
of	O
the	O
search	O
engine	O
.	O
</s>
<s>
Bing	B-Application
has	O
employed	O
the	O
use	O
of	O
prefetching	O
and	O
preloading	O
since	O
the	O
release	O
of	O
Internet	B-Application
Explorer	I-Application
11	I-Application
(	O
October	O
2013	O
)	O
.	O
</s>
<s>
An	O
issue	O
inherent	O
to	O
indiscriminate	O
link	B-Protocol
prefetching	I-Protocol
involves	O
the	O
misuse	O
of	O
"	O
safe	O
"	O
HTTP	O
methods	O
.	O
</s>
<s>
Additionally	O
,	O
there	O
are	O
a	O
number	O
of	O
criticisms	O
regarding	O
the	O
privacy	O
and	O
resource	O
usage	O
implications	O
of	O
link	B-Protocol
prefetching	I-Protocol
:	O
</s>
<s>
Web	O
statistics	O
such	O
as	O
browser	O
usage	O
,	O
search	O
engine	O
referers	B-Protocol
,	O
and	O
page	O
hits	O
may	O
become	O
less	O
reliable	O
due	O
to	O
registering	O
page	O
hits	O
that	O
were	O
never	O
seen	O
by	O
the	O
user	O
.	O
</s>
<s>
In	O
the	O
case	O
of	O
prerendering	O
,	O
Google	B-Application
warns	O
that	O
improper	O
use	O
may	O
result	O
in	O
the	O
aforementioned	O
increased	O
bandwidth	O
usage	O
,	O
slower	O
loading	O
of	O
other	O
links	O
,	O
and	O
slightly	O
stale	O
content	O
.	O
</s>
