<s>
HTTP	B-Protocol
Client	I-Protocol
Hints	I-Protocol
(	O
or	O
simply	O
Client	B-Protocol
Hints	I-Protocol
)	O
are	O
a	O
set	O
of	O
HTTP	B-Protocol
Header	I-Protocol
Fields	I-Protocol
for	O
proactive	O
content	B-Protocol
negotiation	I-Protocol
in	O
the	O
Hypertext	B-Protocol
Transfer	I-Protocol
Protocol	I-Protocol
(	O
HTTP	B-Protocol
)	O
.	O
</s>
<s>
The	O
client	O
can	O
advertise	O
information	O
about	O
itself	O
through	O
these	O
fields	O
so	O
the	O
server	B-Application
can	O
determine	O
which	O
resources	O
should	O
be	O
included	O
in	O
its	O
response	O
.	O
</s>
<s>
As	O
an	O
abstract	O
example	O
,	O
the	O
server	B-Application
might	O
indicate	O
in	O
an	O
Accept-CH	O
response	O
header	O
of	O
an	O
initial	O
request	O
that	O
it	O
can	O
accept	O
device	O
pixel	O
ratio	O
information	O
from	O
the	O
client	O
.	O
</s>
<s>
The	O
client	O
will	O
then	O
make	O
future	O
requests	O
using	O
a	O
header	O
field	O
containing	O
these	O
details	O
,	O
and	O
the	O
server	B-Application
will	O
respond	O
with	O
images	O
appropriate	O
for	O
that	O
device	O
pixel	O
ratio	O
.	O
</s>
