<s>
DNS	B-Protocol
over	I-Protocol
HTTPS	I-Protocol
(	O
DoH	O
)	O
is	O
a	O
protocol	O
for	O
performing	O
remote	O
Domain	B-Protocol
Name	I-Protocol
System	I-Protocol
(	O
DNS	B-Application
)	O
resolution	O
via	O
the	O
HTTPS	B-Protocol
protocol	O
.	O
</s>
<s>
A	O
goal	O
of	O
the	O
method	O
is	O
to	O
increase	O
user	O
privacy	O
and	O
security	O
by	O
preventing	O
eavesdropping	O
and	O
manipulation	O
of	O
DNS	B-Application
data	O
by	O
man-in-the-middle	O
attacks	O
by	O
using	O
the	O
HTTPS	B-Protocol
protocol	O
to	O
encrypt	O
the	O
data	O
between	O
the	O
DoH	O
client	O
and	O
the	O
DoH-based	O
DNS	B-Application
resolver	O
.	O
</s>
<s>
By	O
March	O
2018	O
,	O
Google	B-Application
and	O
the	B-Operating_System
Mozilla	I-Operating_System
Foundation	I-Operating_System
had	O
started	O
testing	O
versions	O
of	O
DNS	B-Protocol
over	I-Protocol
HTTPS	I-Protocol
.	O
</s>
<s>
In	O
February	O
2020	O
,	O
Firefox	B-Application
switched	O
to	O
DNS	B-Protocol
over	I-Protocol
HTTPS	I-Protocol
by	O
default	O
for	O
users	O
in	O
the	O
United	O
States	O
.	O
</s>
<s>
An	O
alternative	O
to	O
DoH	O
is	O
the	O
DNS	B-Protocol
over	I-Protocol
TLS	I-Protocol
(	O
DoT	B-Protocol
)	O
protocol	O
,	O
a	O
similar	O
standard	O
for	O
encrypting	O
DNS	B-Protocol
queries	I-Protocol
,	O
differing	O
only	O
in	O
the	O
methods	O
used	O
for	O
encryption	O
and	O
delivery	O
.	O
</s>
<s>
It	O
uses	O
HTTP/2	B-Protocol
and	O
HTTPS	B-Protocol
,	O
and	O
supports	O
the	O
wire	O
format	O
DNS	B-Application
response	O
data	O
,	O
as	O
returned	O
in	O
existing	O
UDP	O
responses	O
,	O
in	O
an	O
HTTPS	B-Protocol
payload	O
with	O
the	O
MIME	B-Application
type	I-Application
application/dns	O
-message	O
.	O
</s>
<s>
If	O
HTTP/2	B-Protocol
is	O
used	O
,	O
the	O
server	O
may	O
also	O
use	O
HTTP/2	B-Protocol
server	I-Protocol
push	I-Protocol
to	O
send	O
values	O
that	O
it	O
anticipates	O
the	O
client	O
may	O
find	O
useful	O
in	O
advance	O
.	O
</s>
<s>
In	O
addition	O
,	O
other	O
industry	O
working	O
groups	O
such	O
as	O
the	O
,	O
have	O
been	O
formed	O
to	O
"	O
define	O
and	O
adopt	O
DNS	B-Application
encryption	O
technologies	O
in	O
a	O
manner	O
that	O
ensures	O
the	O
continued	O
high	O
performance	O
,	O
resiliency	O
,	O
stability	O
and	O
security	O
of	O
the	O
Internet	O
's	O
critical	O
namespace	O
and	O
name	O
resolution	O
services	O
,	O
as	O
well	O
as	O
ensuring	O
the	O
continued	O
unimpaired	O
functionality	O
of	O
security	O
protections	O
,	O
parental	O
controls	O
,	O
and	O
other	O
services	O
that	O
depend	O
upon	O
the	O
DNS	B-Application
"	O
.	O
</s>
<s>
Since	O
DoH	O
cannot	O
be	O
used	O
under	O
some	O
circumstances	O
,	O
like	O
captive	O
portals	O
,	O
web	B-Application
browsers	I-Application
like	O
Firefox	B-Application
can	O
be	O
configured	O
to	O
fallback	O
to	O
insecure	O
DNS	B-Application
.	O
</s>
<s>
Oblivious	O
DoH	O
was	O
originally	O
developed	O
as	O
Oblivious	O
DNS	B-Application
(	O
ODNS	O
)	O
by	O
researchers	O
at	O
Princeton	O
University	O
and	O
the	O
University	O
of	O
Chicago	O
as	O
an	O
extension	O
to	O
unencrypted	O
DNS	B-Application
,	O
before	O
DoH	O
itself	O
was	O
standardized	O
and	O
widely	O
deployed	O
.	O
</s>
<s>
Apple	O
and	O
Cloudflare	B-Application
subsequently	O
deployed	O
the	O
technology	O
in	O
the	O
context	O
of	O
DoH	O
,	O
as	O
Oblivious	O
DoH	O
(	O
ODoH	O
)	O
.	O
</s>
<s>
In	O
ODoH	O
and	O
ODNS	O
,	O
all	O
DNS	B-Application
requests	O
and	O
responses	O
routed	O
via	O
a	O
proxy	O
,	O
hiding	O
clients	O
 '	O
addresses	O
from	O
the	O
resolver	O
.	O
</s>
<s>
DoH	O
is	O
used	O
for	O
recursive	O
DNS	B-Application
resolution	O
by	O
DNS	B-Application
resolvers	O
.	O
</s>
<s>
Using	O
a	O
DoH	O
implementation	O
within	O
an	O
application	O
:	O
Some	O
browsers	B-Application
have	O
a	O
built-in	O
DoH	O
implementation	O
and	O
can	O
thus	O
perform	O
queries	O
by	O
bypassing	O
the	O
operating	B-General_Concept
system	I-General_Concept
's	O
DNS	B-Application
functionality	O
.	O
</s>
<s>
Installing	O
a	O
DoH	O
proxy	O
on	O
the	O
name	O
server	O
in	O
the	O
local	O
network	O
:	O
In	O
this	O
scenario	O
client	O
systems	O
continue	O
to	O
use	O
traditional	O
(	O
port	O
53	O
or	O
853	O
)	O
DNS	B-Application
to	O
query	O
the	O
name	O
server	O
in	O
the	O
local	O
network	O
,	O
which	O
will	O
then	O
gather	O
the	O
necessary	O
replies	O
via	O
DoH	O
by	O
reaching	O
DoH-servers	O
in	O
the	O
Internet	O
.	O
</s>
<s>
Installing	O
a	O
DoH	O
proxy	O
on	O
a	O
local	O
system	O
:	O
In	O
this	O
scenario	O
,	O
operating	B-General_Concept
systems	I-General_Concept
are	O
configured	O
to	O
query	O
a	O
locally	O
running	O
DoH	O
proxy	O
.	O
</s>
<s>
Apple	O
's	O
iOS	B-Operating_System
14	I-Operating_System
and	O
macOS	B-Operating_System
11	I-Operating_System
released	O
in	O
late	O
2020	O
support	O
both	O
DoH	O
and	O
DoT	B-Protocol
protocols	O
.	O
</s>
<s>
In	O
November	O
2019	O
,	O
Microsoft	O
announced	O
plans	O
to	O
implement	O
support	O
for	O
encrypted	O
DNS	B-Protocol
protocols	I-Protocol
in	O
Microsoft	B-Application
Windows	I-Application
,	O
beginning	O
with	O
DoH	O
.	O
</s>
<s>
In	O
May	O
2020	O
,	O
Microsoft	O
released	O
Windows	B-Application
10	O
Insider	O
Preview	O
Build	O
19628	O
that	O
included	O
initial	O
support	O
for	O
DoH	O
along	O
with	O
instructions	O
on	O
how	O
to	O
enable	O
it	O
via	O
registry	B-Protocol
and	O
command	B-Application
line	I-Application
interface	I-Application
.	O
</s>
<s>
Windows	B-Application
10	O
Insider	O
Preview	O
Build	O
20185	O
added	O
graphical	O
user	O
interface	O
for	O
specifying	O
a	O
DoH	O
resolver	O
.	O
</s>
<s>
DoH	O
support	O
is	O
not	O
included	O
in	O
Windows	B-Application
10	O
21H2	O
.	O
</s>
<s>
Windows	B-Application
11	I-Application
has	O
DoH	O
support	O
.	O
</s>
<s>
BIND	B-Protocol
9	I-Protocol
,	O
an	O
open	B-License
source	I-License
DNS	B-Application
resolver	O
from	O
Internet	O
Systems	O
Consortium	O
added	O
native	O
support	O
for	O
DoH	O
in	O
version	O
9.17.10	O
.	O
</s>
<s>
DNSdist	O
,	O
an	O
open	B-License
source	I-License
DNS	B-Application
proxy/load	O
balancer	O
from	O
PowerDNS	B-Language
,	O
added	O
native	O
support	O
for	O
DoH	O
in	O
version	O
1.4.0	O
in	O
April	O
2019	O
.	O
</s>
<s>
Unbound	B-Protocol
,	O
an	O
open	B-License
source	I-License
DNS	B-Application
resolver	O
created	O
by	O
NLnet	B-General_Concept
Labs	I-General_Concept
,	O
has	O
supported	O
DoH	O
since	O
version	O
1.12.0	O
,	O
released	O
in	O
October	O
2020	O
.	O
</s>
<s>
It	O
first	O
implemented	O
support	O
for	O
DNS	B-Application
encryption	O
using	O
the	O
alternative	O
DoT	B-Protocol
protocol	O
much	O
earlier	O
,	O
starting	O
with	O
version	O
1.4.14	O
,	O
released	O
in	O
December	O
2011	O
.	O
</s>
<s>
Unbound	B-Protocol
runs	O
on	O
most	O
operating	B-General_Concept
systems	I-General_Concept
,	O
including	O
distributions	O
of	O
Linux	B-Application
,	O
MacOS	B-Application
,	O
and	O
Windows	B-Application
.	O
</s>
<s>
DNS	B-Protocol
over	I-Protocol
HTTPS	I-Protocol
is	O
available	O
in	O
Google	B-Application
Chrome	I-Application
83	O
or	O
later	O
for	O
Windows	B-Application
,	O
Linux	B-Application
,	O
and	O
macOS	B-Application
,	O
configurable	O
via	O
the	O
settings	O
page	O
.	O
</s>
<s>
When	O
enabled	O
,	O
and	O
the	O
operating	B-General_Concept
system	I-General_Concept
is	O
configured	O
with	O
a	O
supported	O
DNS	B-Application
server	O
,	O
Chrome	B-Application
will	O
upgrade	O
DNS	B-Protocol
queries	I-Protocol
to	O
be	O
encrypted	O
.	O
</s>
<s>
In	O
September	O
2020	O
,	O
Google	B-Application
Chrome	I-Application
for	O
Android	O
began	O
staged	O
rollout	O
of	O
DNS	B-Protocol
over	I-Protocol
HTTPS	I-Protocol
.	O
</s>
<s>
Users	O
can	O
configure	O
a	O
custom	O
resolver	O
or	O
disable	O
DNS	B-Protocol
over	I-Protocol
HTTPS	I-Protocol
in	O
settings	O
.	O
</s>
<s>
Google	B-Application
Chrome	I-Application
has	O
5	O
DNS	B-Protocol
over	I-Protocol
HTTPS	I-Protocol
providers	O
pre-configured	O
which	O
are	O
Google	B-Protocol
Public	I-Protocol
DNS	I-Protocol
,	O
Cloudflare	B-Application
1.1.1.1	B-Protocol
,	O
Quad	O
9.9.9.9	O
,	O
NextDNS	O
,	O
and	O
CleanBrowsing	B-Protocol
.	O
</s>
<s>
Microsoft	B-Application
Edge	I-Application
supports	O
DNS	B-Protocol
over	I-Protocol
HTTPS	I-Protocol
,	O
configurable	O
via	O
the	O
settings	O
page	O
.	O
</s>
<s>
When	O
enabled	O
,	O
and	O
the	O
operating	B-General_Concept
system	I-General_Concept
is	O
configured	O
with	O
a	O
supported	O
DNS	B-Application
server	O
,	O
Edge	O
will	O
upgrade	O
DNS	B-Protocol
queries	I-Protocol
to	O
be	O
encrypted	O
.	O
</s>
<s>
In	O
2018	O
,	O
Mozilla	B-Operating_System
partnered	O
with	O
Cloudflare	B-Application
to	O
deliver	O
DoH	O
for	O
Firefox	B-Application
users	O
that	O
enable	O
it	O
(	O
known	O
as	O
Trusted	O
Recursive	O
Resolver	O
)	O
.	O
</s>
<s>
On	O
February	O
25	O
,	O
2020	O
,	O
Firefox	B-Application
started	O
enabling	O
DNS	B-Protocol
over	I-Protocol
HTTPS	I-Protocol
for	O
all	O
US-based	O
users	O
,	O
relying	O
on	O
Cloudflare	B-Application
's	O
resolver	O
by	O
default	O
.	O
</s>
<s>
Opera	B-Application
supports	O
DoH	O
,	O
configurable	O
via	O
the	O
browser	B-Application
settings	O
page	O
.	O
</s>
<s>
By	O
default	O
,	O
DNS	B-Protocol
queries	I-Protocol
are	O
sent	O
to	O
Cloudflare	B-Application
servers	O
.	O
</s>
<s>
DNS	B-Protocol
over	I-Protocol
HTTPS	I-Protocol
server	O
implementations	O
are	O
already	O
available	O
free	O
of	O
charge	O
by	O
some	O
public	O
DNS	B-Application
providers	O
.	O
</s>
<s>
DoH	O
can	O
impede	O
analysis	O
and	O
monitoring	O
of	O
DNS	B-Application
traffic	O
for	O
cybersecurity	O
purposes	O
;	O
the	O
2019	O
DDoS	O
worm	O
Godlua	O
used	O
DoH	O
to	O
mask	O
connections	O
to	O
its	O
command-and-control	O
server	O
.	O
</s>
<s>
In	O
January	O
2021	O
,	O
NSA	O
warned	O
enterprises	O
against	O
using	O
external	O
DoH	O
resolvers	O
because	O
they	O
prevent	O
DNS	B-Protocol
query	I-Protocol
filtering	O
,	O
inspection	O
,	O
and	O
audit	O
.	O
</s>
<s>
DoH	O
has	O
been	O
used	O
to	O
bypass	O
parental	O
controls	O
which	O
operate	O
at	O
the	O
(	O
unencrypted	O
)	O
standard	O
DNS	B-Application
level	O
;	O
Circle	O
,	O
a	O
parental	O
control	O
router	O
which	O
relies	O
on	O
DNS	B-Protocol
queries	I-Protocol
to	O
check	O
domains	O
against	O
a	O
blocklist	O
,	O
blocks	O
DoH	O
by	O
default	O
due	O
to	O
this	O
.	O
</s>
<s>
However	O
,	O
there	O
are	O
DNS	B-Application
providers	O
that	O
offer	O
filtering	O
and	O
parental	O
controls	O
along	O
with	O
support	O
for	O
DoH	O
by	O
operating	O
DoH	O
servers	O
.	O
</s>
<s>
The	O
Internet	O
Service	O
Providers	O
Association	O
(	O
ISPA	O
)	O
—	O
a	O
trade	O
association	O
representing	O
British	O
ISPs	O
—	O
and	O
the	O
also	O
British	O
body	O
Internet	O
Watch	O
Foundation	O
have	O
criticized	O
Mozilla	B-Operating_System
,	O
developer	O
of	O
the	O
Firefox	B-Application
web	I-Application
browser	I-Application
,	O
for	O
supporting	O
DoH	O
,	O
as	O
they	O
believe	O
that	O
it	O
will	O
undermine	O
web	O
blocking	O
programs	O
in	O
the	O
country	O
,	O
including	O
ISP	O
default	O
filtering	O
of	O
adult	O
content	O
,	O
and	O
mandatory	O
court-ordered	O
filtering	O
of	O
copyright	O
violations	O
.	O
</s>
<s>
The	O
ISPA	O
nominated	O
Mozilla	B-Operating_System
for	O
its	O
"	O
Internet	O
Villain	O
"	O
award	O
for	O
2019	O
(	O
alongside	O
the	O
EU	O
Directive	O
on	O
Copyright	O
in	O
the	O
Digital	O
Single	O
Market	O
,	O
and	O
Donald	O
Trump	O
)	O
,	O
"	O
for	O
their	O
proposed	O
approach	O
to	O
introduce	O
DNS-over-HTTPS	B-Protocol
in	O
such	O
a	O
way	O
as	O
to	O
bypass	O
UK	O
filtering	O
obligations	O
and	O
parental	O
controls	O
,	O
undermining	O
internet	O
safety	O
standards	O
in	O
the	O
UK.	O
"	O
</s>
<s>
Mozilla	B-Operating_System
responded	O
to	O
the	O
allegations	O
by	O
the	O
ISPA	O
,	O
arguing	O
that	O
it	O
would	O
not	O
prevent	O
filtering	O
,	O
and	O
that	O
they	O
were	O
"	O
surprised	O
and	O
disappointed	O
that	O
an	O
industry	O
association	O
for	O
ISPs	O
decided	O
to	O
misrepresent	O
an	O
improvement	O
to	O
decades-old	O
internet	O
infrastructure	O
"	O
.	O
</s>
<s>
Mozilla	B-Operating_System
subsequently	O
stated	O
that	O
DoH	O
will	O
not	O
be	O
used	O
by	O
default	O
in	O
the	O
British	O
market	O
until	O
further	O
discussion	O
with	O
relevant	O
stakeholders	O
,	O
but	O
stated	O
that	O
it	O
"	O
would	O
offer	O
real	O
security	O
benefits	O
to	O
UK	O
citizens	O
"	O
.	O
</s>
