<s>
PDF.js	B-Operating_System
is	O
a	O
JavaScript	B-Language
library	I-Language
that	O
renders	O
Portable	B-Application
Document	I-Application
Format	I-Application
(	O
PDF	B-Application
)	O
files	O
using	O
the	O
web	O
standards-compliant	O
HTML5	B-Language
Canvas	I-Language
.	O
</s>
<s>
The	O
project	O
is	O
led	O
by	O
the	O
Mozilla	B-Operating_System
Corporation	O
after	O
Andreas	O
Gal	O
launched	O
it	O
(	O
initially	O
as	O
an	O
experiment	O
)	O
in	O
2011	O
.	O
</s>
<s>
PDF.js	B-Operating_System
was	O
originally	O
created	O
as	O
an	O
extension	B-Protocol
for	O
Firefox	B-Application
and	O
is	O
included	O
in	O
Firefox	B-Application
since	O
2012	O
.	O
</s>
<s>
The	O
project	O
was	O
created	O
to	O
provide	O
a	O
way	O
for	O
viewing	O
PDF	B-Application
documents	I-Application
natively	O
in	O
the	O
web	B-Application
browser	I-Application
,	O
which	O
prevents	O
potential	O
security	O
risks	O
when	O
opening	O
PDF	B-Application
documents	I-Application
outside	O
a	O
browser	B-Application
,	O
as	O
the	O
code	O
for	O
displaying	O
the	O
document	O
is	O
sandboxed	O
in	O
a	O
browser	B-Application
.	O
</s>
<s>
Its	O
implementation	O
uses	O
the	O
Canvas	B-Language
element	I-Language
from	O
HTML5	B-Application
,	O
which	O
allows	O
for	O
fast	O
rendering	O
speeds	O
.	O
</s>
<s>
PDF.js	B-Operating_System
is	O
used	O
in	O
Thunderbird	B-Application
,	O
ownCloud	B-Language
,	O
Nextcloud	B-General_Concept
,	O
and	O
as	O
browser	B-Protocol
extensions	I-Protocol
for	O
Google	O
Chrome/Chromium	O
,	O
Firefox	B-Application
for	I-Application
Android	I-Application
,	O
Pale	B-Protocol
Moon	I-Protocol
and	O
SeaMonkey	B-Language
.	O
</s>
<s>
It	O
can	O
be	O
integrated	O
or	O
embedded	O
in	O
a	O
web	O
or	O
native	O
application	O
to	O
enable	O
PDF	B-Application
rendering	O
and	O
viewing	O
,	O
and	O
allows	O
advanced	O
usages	O
such	O
as	O
Server-side	B-Language
rendering	I-Language
.	O
</s>
<s>
Many	O
web	O
applications	O
,	O
including	O
Dropbox	B-Application
,	O
Slack	B-Protocol
,	O
and	O
LinkedIn	O
Learning	O
integrate	O
PDF.js	B-Operating_System
to	O
enable	O
previewing	O
PDF	B-Application
documents	I-Application
.	O
</s>
<s>
According	O
a	O
benchmark	O
by	O
Mozilla	B-Operating_System
,	O
PDF.js	B-Operating_System
is	O
performant	O
for	O
viewing	O
most	O
common	O
PDF	B-Application
files	I-Application
,	O
while	O
it	O
may	O
have	O
some	O
issues	O
with	O
large	O
or	O
'	O
graphics-heavy	O
'	O
documents	O
.	O
</s>
<s>
PDF.js	B-Operating_System
supports	O
most	O
of	O
the	O
PDF	B-Application
specifications	O
(	O
including	O
form	O
support	O
or	O
XFA	B-Language
)	O
,	O
but	O
some	O
features	O
have	O
not	O
been	O
implemented	O
yet	O
,	O
which	O
may	O
impact	O
rendering	O
behavior	O
depending	O
on	O
the	O
features	O
the	O
document	O
uses	O
.	O
</s>
<s>
Several	O
PDF/X	O
or	O
optional	O
PDF	B-Application
features	O
that	O
are	O
not	O
supported	O
in	O
PDF.js	B-Operating_System
include	O
:	O
</s>
<s>
The	O
PDF.js	B-Operating_System
contributor	O
community	O
also	O
notes	O
that	O
the	O
browser	B-Application
behavior	O
of	O
PDF.js	B-Operating_System
varies	O
with	O
browser	B-Application
support	O
for	O
PDF.js	B-Operating_System
'	O
s	O
required	O
features	O
.	O
</s>
<s>
Performance	O
and	O
reliability	O
will	O
be	O
the	O
best	O
on	O
Chrome	B-Application
and	O
Firefox	B-Application
,	O
which	O
are	O
fully	O
supported	O
and	O
subject	O
to	O
automated	O
testing	O
.	O
</s>
