<s>
Canvas	B-Protocol
fingerprinting	I-Protocol
is	O
one	O
of	O
a	O
number	O
of	O
browser	B-Protocol
fingerprinting	I-Protocol
techniques	O
for	O
tracking	B-Application
online	I-Application
users	I-Application
that	O
allow	O
websites	O
to	O
identify	O
and	O
track	O
visitors	O
using	O
the	O
HTML5	B-Language
canvas	I-Language
element	O
instead	O
of	O
browser	B-Application
cookies	I-Application
or	O
other	O
similar	O
means	O
.	O
</s>
<s>
Canvas	B-Protocol
fingerprinting	I-Protocol
works	O
by	O
exploiting	O
the	O
HTML5	B-Language
canvas	I-Language
element	O
.	O
</s>
<s>
Variations	O
in	O
which	O
the	O
graphics	B-Architecture
processing	I-Architecture
unit	I-Architecture
(	O
GPU	B-Architecture
)	O
,	O
or	O
the	O
graphics	B-Application
driver	I-Application
,	O
is	O
installed	O
may	O
cause	O
the	O
fingerprint	O
variation	O
.	O
</s>
<s>
It	O
is	O
claimed	O
that	O
because	O
the	O
technique	O
is	O
effectively	O
fingerprinting	O
the	O
GPU	B-Architecture
,	O
the	O
entropy	O
is	O
"	O
orthogonal	O
"	O
to	O
the	O
entropy	O
of	O
previous	O
browser	B-Protocol
fingerprint	I-Protocol
techniques	O
such	O
as	O
screen	B-General_Concept
resolution	I-General_Concept
and	O
browser	O
JavaScript	B-Language
capabilities	O
.	O
</s>
<s>
In	O
May	O
2012	O
,	O
Keaton	O
Mowery	O
and	O
Hovav	O
Shacham	O
,	O
researchers	O
at	O
University	O
of	O
California	O
,	O
San	O
Diego	O
,	O
wrote	O
a	O
paper	O
Pixel	O
Perfect	O
:	O
Fingerprinting	O
Canvas	B-Language
in	O
HTML5	B-Application
describing	O
how	O
the	O
HTML5	B-Language
canvas	I-Language
could	O
be	O
used	O
to	O
create	O
digital	O
fingerprints	O
of	O
web	O
users	O
.	O
</s>
<s>
Social	O
bookmarking	O
technology	O
company	O
AddThis	O
began	O
experimenting	O
with	O
canvas	B-Protocol
fingerprinting	I-Protocol
early	O
in	O
2014	O
as	O
a	O
potential	O
replacement	O
for	O
cookies	B-Application
.	O
</s>
<s>
5%	O
of	O
the	O
top	O
100,000	O
websites	O
used	O
canvas	B-Protocol
fingerprinting	I-Protocol
while	O
it	O
was	O
deployed	O
.	O
</s>
<s>
Users	O
will	O
be	O
able	O
to	O
install	O
an	O
opt-out	O
cookie	B-Application
on	O
any	O
computer	O
to	O
prevent	O
being	O
tracked	O
by	O
AddThis	O
with	O
canvas	B-Protocol
fingerprinting	I-Protocol
.	O
</s>
<s>
A	O
software	O
developer	O
writing	O
in	O
Forbes	O
stated	O
that	O
device	B-Protocol
fingerprinting	I-Protocol
has	O
been	O
utilized	O
for	O
the	O
purpose	O
of	O
preventing	O
unauthorized	O
access	O
to	O
systems	O
long	O
before	O
it	O
was	O
used	O
for	O
tracking	O
users	O
without	O
their	O
consent	O
.	O
</s>
<s>
In	O
2022	O
,	O
the	O
capabilities	O
of	O
canvas	B-Protocol
fingerprinting	I-Protocol
were	O
much	O
deepened	O
by	O
taking	O
minute	O
differences	O
between	O
nominally	O
identical	O
units	O
of	O
the	O
same	O
GPU	B-Architecture
model	O
into	O
account	O
.	O
</s>
<s>
Tor	O
Project	O
reference	O
documentation	O
states	O
,	O
"	O
After	O
plugins	O
and	O
plugin-provided	O
information	O
,	O
we	O
believe	O
that	O
the	O
HTML5	B-Language
Canvas	I-Language
is	O
the	O
single	O
largest	O
fingerprinting	O
threat	O
browsers	O
face	O
today.	O
"	O
</s>
<s>
Tor	O
Browser	O
notifies	O
the	O
user	O
of	O
canvas	B-Language
read	O
attempts	O
and	O
provides	O
the	O
option	O
to	O
return	O
blank	O
image	O
data	O
to	O
prevent	O
fingerprinting	O
.	O
</s>
<s>
However	O
,	O
Tor	O
Browser	O
is	O
currently	O
unable	O
to	O
distinguish	O
between	O
legitimate	O
uses	O
of	O
the	O
canvas	B-Language
element	I-Language
and	O
fingerprinting	O
efforts	O
,	O
so	O
its	O
warning	O
cannot	O
be	O
taken	O
as	O
proof	O
of	O
a	O
website	O
's	O
intent	O
to	O
identify	O
and	O
track	O
its	O
visitors	O
.	O
</s>
<s>
Browser	O
add-ons	B-Operating_System
like	O
Privacy	B-Operating_System
Badger	I-Operating_System
,	O
DoNotTrackMe	B-Operating_System
,	O
or	O
Adblock	B-Application
Plus	I-Application
manually	O
enhanced	O
with	O
EasyPrivacy	O
list	O
are	O
able	O
to	O
block	O
third-party	O
ad	O
network	O
trackers	O
and	O
can	O
be	O
configured	O
to	O
block	O
canvas	B-Protocol
fingerprinting	I-Protocol
,	O
provided	O
that	O
the	O
tracker	O
is	O
served	O
by	O
a	O
third	O
party	O
server	O
(	O
as	O
opposed	O
to	O
being	O
implemented	O
by	O
the	O
visited	O
website	O
itself	O
)	O
.	O
</s>
<s>
Canvas	B-Language
Defender	O
,	O
a	O
browser	O
add-on	B-Operating_System
,	O
spoofs	O
Canvas	B-Language
fingerprints	O
.	O
</s>
<s>
The	O
LibreWolf	O
browser	O
project	O
includes	O
technology	O
to	O
block	O
access	O
to	O
the	O
HTML5	B-Language
canvas	I-Language
by	O
default	O
,	O
only	O
allowing	O
it	O
in	O
specific	O
instances	O
green-lit	O
by	O
the	O
user	O
.	O
</s>
