<s>
Google	B-Application
Native	I-Application
Client	I-Application
(	O
NaCl	B-Application
)	O
was	O
a	O
sandboxing	O
technology	O
for	O
running	O
either	O
a	O
subset	O
of	O
Intel	B-Operating_System
x86	I-Operating_System
,	O
ARM	B-Architecture
,	O
or	O
MIPS	B-Device
native	B-Language
code	I-Language
,	O
or	O
a	O
portable	O
executable	O
,	O
in	O
a	O
sandbox	O
.	O
</s>
<s>
It	O
allows	O
safely	O
running	O
native	B-Language
code	I-Language
from	O
a	O
web	B-Application
browser	I-Application
,	O
independent	O
of	O
the	O
user	O
operating	B-General_Concept
system	I-General_Concept
,	O
allowing	O
web	B-Application
apps	I-Application
to	O
run	O
at	O
near-native	O
speeds	O
,	O
which	O
aligns	O
with	O
Google	B-Application
's	I-Application
plans	O
for	O
ChromeOS	B-Operating_System
.	O
</s>
<s>
It	O
may	O
also	O
be	O
used	O
for	O
securing	O
browser	B-Application
plugins	B-Application
,	O
and	O
parts	O
of	O
other	O
applications	O
or	O
full	O
applications	O
such	O
as	O
ZeroVM	B-Application
.	O
</s>
<s>
To	O
demonstrate	O
the	O
readiness	O
of	O
the	O
technology	O
,	O
on	O
9	O
December	O
2011	O
,	O
Google	B-Application
announced	O
the	O
availability	O
of	O
several	O
new	O
Chrome-only	O
versions	O
of	O
games	O
known	O
for	O
their	O
rich	O
and	O
processor-intensive	O
graphics	O
,	O
including	O
Bastion	B-Application
(	O
no	O
longer	O
supported	O
on	O
the	O
Chrome	B-Application
Web	I-Application
Store	I-Application
)	O
.	O
</s>
<s>
NaCl	B-Application
runs	O
hardware-accelerated	B-General_Concept
3D	O
graphics	O
(	O
via	O
OpenGL	B-Application
ES	I-Application
2.0	O
)	O
,	O
sandboxed	O
local	O
file	O
storage	O
,	O
dynamic	B-Operating_System
loading	I-Operating_System
,	O
full	O
screen	O
mode	O
,	O
and	O
mouse	B-Device
capture	O
.	O
</s>
<s>
There	O
were	O
also	O
plans	O
to	O
make	O
NaCl	B-Application
available	O
on	O
handheld	O
devices	O
.	O
</s>
<s>
Portable	B-Application
Native	I-Application
Client	I-Application
(	O
PNaCl	O
)	O
is	O
an	O
architecture-independent	O
version	O
.	O
</s>
<s>
PNaCl	O
apps	O
are	O
compiled	B-Application
ahead-of-time	I-Application
.	O
</s>
<s>
PNaCl	O
is	O
recommended	O
over	O
NaCl	B-Application
for	O
most	O
use	O
cases	O
.	O
</s>
<s>
The	O
general	O
concept	O
of	O
NaCl	B-Application
(	O
running	O
native	B-Language
code	I-Language
in	O
web	B-Application
browser	I-Application
)	O
has	O
been	O
implemented	O
before	O
in	O
ActiveX	B-Application
,	O
which	O
,	O
while	O
still	O
in	O
use	O
,	O
has	O
full	O
access	O
to	O
the	O
system	O
(	O
disk	O
,	O
memory	O
,	O
user-interface	O
,	O
registry	O
,	O
etc	O
.	O
)	O
.	O
</s>
<s>
Native	B-Application
Client	I-Application
avoids	O
this	O
issue	O
by	O
using	O
sandboxing	O
.	O
</s>
<s>
An	O
alternative	O
by	O
Mozilla	B-Operating_System
was	O
asm.js	B-Language
,	O
which	O
also	O
allows	O
applications	O
written	O
in	O
C	B-Language
or	O
C++	B-Language
to	O
be	O
compiled	O
to	O
run	O
in	O
the	O
browser	B-Application
and	O
also	O
supports	O
ahead-of-time	B-Application
compilation	I-Application
,	O
but	O
is	O
a	O
subset	O
of	O
JavaScript	B-Language
and	O
hence	O
backwards-compatible	O
with	O
browsers	B-Application
that	O
do	O
not	O
support	O
it	O
directly	O
.	O
</s>
<s>
On	O
12	O
October	O
2016	O
,	O
a	O
comment	O
on	O
the	O
Chromium	B-Language
issue	O
tracker	O
indicated	O
that	O
Google	B-Application
's	I-Application
Pepper	O
and	O
Native	B-Application
Client	I-Application
teams	O
had	O
been	O
destaffed	O
.	O
</s>
<s>
On	O
30	O
May	O
2017	O
,	O
Google	B-Application
announced	O
deprecation	O
of	O
PNaCl	O
in	O
favor	O
of	O
WebAssembly	B-Language
.	O
</s>
<s>
Although	O
initially	O
Google	B-Application
planned	O
to	O
remove	O
PNaCl	O
in	O
first	O
quarter	O
of	O
2018	O
,	O
and	O
later	O
in	O
the	O
second	O
quarter	O
of	O
2019	O
,	O
it	O
has	O
been	O
removed	O
in	O
June	O
2022	O
(	O
together	O
with	O
Chrome	B-Operating_System
Apps	I-Operating_System
)	O
.	O
</s>
<s>
Native	B-Application
Client	I-Application
is	O
an	O
open-source	B-Application
project	O
being	O
developed	O
by	O
Google	B-Application
.	I-Application
</s>
<s>
To	O
date	O
,	O
Quake	B-Application
,	O
XaoS	B-Algorithm
,	O
Battle	B-Application
for	I-Application
Wesnoth	I-Application
,	O
Doom	B-Application
,	O
Lara	B-Application
Croft	I-Application
and	I-Application
the	I-Application
Guardian	I-Application
of	I-Application
Light	I-Application
,	O
From	B-Application
Dust	I-Application
,	O
and	O
MAME	B-Device
,	O
as	O
well	O
as	O
the	O
sound	O
processing	O
system	O
Csound	B-Application
,	O
have	O
been	O
ported	O
to	O
Native	B-Application
Client	I-Application
.	O
</s>
<s>
Native	B-Application
Client	I-Application
has	O
been	O
available	O
in	O
the	B-Application
Google	I-Application
Chrome	B-Application
web	I-Application
browser	I-Application
since	O
version	O
14	O
,	O
and	O
has	O
been	O
enabled	O
by	O
default	O
since	O
version	O
31	O
,	O
when	O
the	O
Portable	B-Application
Native	I-Application
Client	I-Application
(	O
PNaCl	O
,	O
pronounced	O
:	O
pinnacle	O
)	O
was	O
released	O
.	O
</s>
<s>
An	O
ARM	B-Architecture
implementation	O
was	O
released	O
in	O
March	O
2010	O
.	O
x86-64	B-Device
,	O
IA-32	B-Device
,	O
and	O
MIPS	B-Device
are	O
also	O
supported	O
.	O
</s>
<s>
To	O
run	O
an	O
application	O
portably	O
under	O
PNaCl	O
,	O
it	O
must	O
be	O
compiled	O
to	O
an	O
architecture-agnostic	O
and	O
stable	O
subset	O
of	O
the	O
LLVM	B-Application
intermediate	B-Application
representation	I-Application
bytecode	O
.	O
</s>
<s>
The	O
PNaCl	O
Toolchain	O
makes	O
.pexe	O
files	O
;	O
NaCl	B-Application
Toolchain	O
.nexe	B-Application
files	O
.	O
</s>
<s>
The	O
magic	O
number	O
of	O
.nexe	B-Application
files	O
is	O
0x7F	O
'	O
E	O
 '	O
'	O
L	O
 '	O
'	O
F	O
 '	O
,	O
which	O
is	O
ELF	O
.	O
</s>
<s>
In	O
Chrome	B-Application
,	O
they	O
are	O
translated	O
to	O
architecture-specific	O
executables	O
so	O
that	O
they	O
can	O
be	O
run	O
.	O
</s>
<s>
NaCl	B-Application
uses	O
software	O
fault	O
detection	O
and	O
isolation	O
for	O
sandboxing	O
on	O
x86-64	B-Device
and	O
ARM	B-Architecture
.	O
</s>
<s>
The	O
x86-32	B-Device
implementation	O
of	O
Native	B-Application
Client	I-Application
is	O
notable	O
for	O
its	O
novel	O
sandboxing	O
method	O
,	O
which	O
makes	O
use	O
of	O
the	O
x86	B-Operating_System
architecture	I-Operating_System
's	O
rarely	O
used	O
segmentation	B-Device
facility	I-Device
.	O
</s>
<s>
Native	B-Application
Client	I-Application
sets	O
up	O
x86	B-Operating_System
segments	O
to	O
restrict	O
the	O
memory	O
range	O
that	O
the	O
sandboxed	O
code	O
can	O
access	O
.	O
</s>
<s>
To	O
prevent	O
the	O
code	O
from	O
jumping	O
to	O
an	O
unsafe	O
instruction	O
hidden	O
in	O
the	O
middle	O
of	O
a	O
safe	O
instruction	O
,	O
Native	B-Application
Client	I-Application
requires	O
that	O
all	O
indirect	O
jumps	O
be	O
jumps	O
to	O
the	O
start	O
of	O
32-byte-aligned	O
blocks	O
,	O
and	O
instructions	O
are	O
not	O
allowed	O
to	O
straddle	O
these	O
blocks	O
.	O
</s>
<s>
Because	O
of	O
these	O
constraints	O
,	O
C	B-Language
and	O
C++	B-Language
code	I-Language
must	O
be	O
recompiled	O
to	O
run	O
under	O
Native	B-Application
Client	I-Application
,	O
which	O
provides	O
customized	O
versions	O
of	O
the	O
GNU	B-Application
toolchain	I-Application
,	O
specifically	O
GNU	B-Application
Compiler	I-Application
Collection	I-Application
(	O
GCC	B-Application
)	O
,	O
GNU	B-Application
Binutils	I-Application
,	O
and	O
LLVM	B-Application
.	O
</s>
<s>
Native	B-Application
Client	I-Application
is	O
licensed	O
under	O
a	O
BSD-style	B-Operating_System
license	I-Operating_System
.	O
</s>
<s>
Native	B-Application
Client	I-Application
uses	O
Newlib	B-Language
as	O
its	O
C	B-Language
library	I-Language
,	O
but	O
a	O
port	O
of	O
GNU	B-Language
C	I-Language
Library	I-Language
(	O
GNU	B-Language
libc	I-Language
)	O
is	O
also	O
available	O
.	O
</s>
<s>
NaCl	B-Application
denotes	O
sodium	O
chloride	O
,	O
common	O
table	O
salt	O
;	O
as	O
a	O
pun	B-Application
,	O
the	O
name	O
of	O
pepper	O
was	O
also	O
used	O
.	O
</s>
<s>
Pepper	O
API	O
is	O
a	O
cross-platform	O
,	O
open-source	B-Application
API	O
for	O
creating	O
Native	B-Application
Client	I-Application
modules	O
.	O
</s>
<s>
Pepper	O
Plugin	B-Application
API	O
,	O
or	O
PPAPI	O
is	O
a	O
cross-platform	O
API	O
for	O
Native	O
Client-secured	O
web	B-Application
browser	I-Application
plugins	B-Application
,	O
first	O
based	O
on	O
Netscape	O
's	O
NPAPI	B-Protocol
,	O
then	O
rewritten	O
from	O
scratch	O
.	O
</s>
<s>
It	O
was	O
used	O
in	O
Chromium	B-Language
and	O
Google	B-Application
Chrome	I-Application
to	O
enable	O
the	O
PPAPI	O
version	O
of	O
Adobe	B-Operating_System
Flash	I-Operating_System
and	O
the	O
built-in	O
PDF	B-Application
viewer	O
.	O
</s>
<s>
On	O
12	O
August	O
2009	O
,	O
a	O
page	O
on	O
Google	B-Application
Code	O
introduced	O
a	O
new	O
project	O
,	O
Pepper	O
,	O
and	O
the	O
associated	O
Pepper	O
Plugin	B-Application
API	O
(	O
PPAPI	O
)	O
,	O
"	O
a	O
set	O
of	O
modifications	O
to	O
NPAPI	B-Protocol
to	O
make	O
plugins	B-Application
more	O
portable	O
and	O
more	O
secure	O
"	O
.	O
</s>
<s>
This	O
extension	O
is	O
designed	O
specifically	O
to	O
ease	O
implementing	O
out-of-process	O
plugin	B-Application
execution	O
.	O
</s>
<s>
Further	O
,	O
the	O
goals	O
of	O
the	O
project	O
are	O
to	O
provide	O
a	O
framework	O
for	O
making	O
plugins	B-Application
fully	O
cross-platform	O
.	O
</s>
<s>
Uniform	O
semantics	O
for	O
NPAPI	B-Protocol
across	O
browsers	B-Application
.	O
</s>
<s>
Execution	O
in	O
a	O
separate	O
process	B-Operating_System
from	O
the	O
renderer-browser	O
.	O
</s>
<s>
Standardize	O
rendering	O
using	O
the	O
browser	B-Application
's	O
compositing	O
process	B-Operating_System
.	O
</s>
<s>
Plugin	B-Application
registry	O
.	O
</s>
<s>
The	O
Pepper	O
API	O
also	O
supports	O
Gamepads	B-Device
(	O
version	O
19	O
)	O
and	O
WebSockets	B-Protocol
(	O
version	O
18	O
)	O
.	O
</s>
<s>
,	O
Google	B-Application
's	I-Application
open	O
source	O
browser	B-Application
,	O
Chromium	B-Language
,	O
was	O
the	O
only	O
web	B-Application
browser	I-Application
to	O
use	O
the	O
new	O
browser	B-Application
plug-in	B-Application
model	O
.	O
</s>
<s>
As	O
of	O
2020	O
,	O
Pepper	O
is	O
supported	O
by	O
Chrome	B-Application
,	O
Chromium	B-Language
and	O
Blink	O
layout	O
engine-based	O
browsers	B-Application
such	O
as	O
Opera	O
and	O
Microsoft	O
Edge	O
.	O
</s>
<s>
In	O
August	O
2020	O
,	O
Google	B-Application
announced	O
that	O
support	O
for	O
PPAPI	O
would	O
be	O
removed	O
from	O
Google	B-Application
Chrome	I-Application
and	O
Chromium	B-Language
in	O
June	O
2022	O
.	O
</s>
<s>
Firefox	B-Application
developers	O
stated	O
in	O
2014	O
that	O
they	O
would	O
not	O
support	O
Pepper	O
,	O
as	O
there	O
is	O
no	O
full	O
specification	O
of	O
the	O
API	O
beyond	O
its	O
implementation	O
in	O
Chrome	B-Application
,	O
which	O
itself	O
is	O
designed	O
for	O
use	O
with	O
Blink	B-Language
layout	I-Language
engine	I-Language
only	O
,	O
and	O
has	O
private	O
APIs	O
specific	O
to	O
the	O
Flash	O
Player	O
plugin	B-Application
which	O
are	O
not	O
documented	O
.	O
</s>
<s>
In	O
October	O
2016	O
Mozilla	B-Operating_System
announced	O
that	O
it	O
had	O
re-considered	O
and	O
was	O
exploring	O
whether	O
to	O
incorporate	O
the	O
Pepper	O
API	O
and	O
PDFium	O
in	O
future	O
releases	O
of	O
Firefox	B-Application
,	O
however	O
no	O
such	O
steps	O
were	O
taken	O
.	O
</s>
<s>
One	O
website	O
uses	O
NaCL	B-Application
on	O
the	O
server	O
to	O
let	O
users	O
experiment	O
with	O
the	O
Go	B-Application
programming	I-Application
language	I-Application
from	O
their	O
browsers	B-Application
.	O
</s>
<s>
Some	O
groups	O
of	O
browser	B-Application
developers	O
support	O
the	O
Native	B-Application
Client	I-Application
technology	O
,	O
but	O
others	O
do	O
not	O
.	O
</s>
<s>
Chad	O
Austin	O
(	O
of	O
IMVU	O
)	O
praised	O
the	O
way	O
Native	B-Application
Client	I-Application
can	O
bring	O
high-performance	O
applications	O
to	O
the	O
web	O
(	O
with	O
about	O
5%	O
penalty	O
compared	O
to	O
native	B-Language
code	I-Language
)	O
in	O
a	O
secure	O
way	O
,	O
while	O
also	O
accelerating	O
the	O
evolution	O
of	O
client-side	O
applications	O
by	O
giving	O
a	O
choice	O
of	O
the	O
programming	O
language	O
used	O
(	O
besides	O
JavaScript	B-Language
)	O
.	O
</s>
<s>
Id	O
Software	O
's	O
John	O
D	O
.	O
Carmack	O
praised	O
Native	B-Application
Client	I-Application
at	O
QuakeCon	O
2012	O
,	O
saying	O
:	O
"	O
if	O
you	O
have	O
to	O
do	O
something	O
inside	O
a	O
browser	B-Application
,	O
Native	B-Application
Client	I-Application
is	O
much	O
more	O
interesting	O
as	O
something	O
that	O
started	O
out	O
as	O
a	O
really	O
pretty	O
darn	O
clever	O
x86	B-Operating_System
hack	O
in	O
the	O
way	O
that	O
they	O
could	O
sandbox	O
all	O
of	O
this	O
in	O
user	O
mode	O
interestingly	O
.	O
</s>
<s>
It	O
's	O
now	O
dynamic	O
recompilation	O
,	O
but	O
something	O
that	O
you	O
program	O
in	O
C	B-Language
or	O
C++	B-Language
and	O
it	O
compiles	O
down	O
to	O
something	O
that	O
's	O
going	O
to	O
be	O
not	O
your	O
-O4	O
optimization	O
level	O
for	O
completely	O
native	B-Language
code	I-Language
but	O
pretty	O
damn	O
close	O
to	O
native	B-Language
code	I-Language
.	O
</s>
<s>
Mozilla	B-Operating_System
's	O
vice	O
president	O
of	O
products	O
,	O
Jay	O
Sullivan	O
,	O
said	O
that	O
Mozilla	B-Operating_System
has	O
no	O
plans	O
to	O
run	O
native	B-Language
code	I-Language
inside	O
the	O
browser	B-Application
,	O
as	O
"	O
These	O
native	O
apps	O
are	O
just	O
little	O
black	O
boxes	O
in	O
a	O
webpage	O
.	O
</s>
<s>
Mozilla	B-Operating_System
's	O
Christopher	O
Blizzard	O
criticized	O
NaCl	B-Application
,	O
claiming	O
that	O
native	B-Language
code	I-Language
cannot	O
evolve	O
in	O
the	O
same	O
way	O
that	O
the	O
source	O
code-driven	O
web	O
can	O
.	O
</s>
<s>
He	O
also	O
compared	O
NaCl	B-Application
to	O
Microsoft	O
's	O
ActiveX	B-Application
technology	O
,	O
plagued	O
with	O
DLL	O
Hell	O
.	O
</s>
<s>
Håkon	O
Wium	O
Lie	O
,	O
Opera	O
's	O
CTO	O
,	O
believes	O
that	O
"	O
NaCl	B-Application
seems	O
to	O
be	O
'	O
yearning	O
for	O
the	O
bad	O
old	O
days	O
,	O
before	O
the	O
web	O
 '	O
"	O
,	O
and	O
that	O
"	O
Native	B-Application
Client	I-Application
is	O
about	O
building	O
a	O
new	O
platform	O
–	O
or	O
porting	O
an	O
old	O
platform	O
into	O
the	O
web	O
 [ ... ] 	O
it	O
will	O
bring	O
in	O
complexity	O
and	O
security	O
issues	O
,	O
and	O
it	O
will	O
take	O
away	O
focus	O
from	O
the	O
web	O
platform.	O
"	O
</s>
<s>
The	O
second	O
generation	O
of	O
sandboxing	O
developed	O
in	O
Google	B-Application
is	O
gVisor	B-Application
.	O
</s>
<s>
It	O
is	O
intended	O
to	O
replace	O
NaCl	B-Application
in	O
Google	B-General_Concept
Cloud	I-General_Concept
,	O
to	O
be	O
more	O
exact	O
in	O
Google	B-Application
App	I-Application
Engine	I-Application
.	O
</s>
<s>
Google	B-Application
also	O
has	O
been	O
promoting	O
WebAssembly	B-Language
.	O
</s>
