<s>
The	O
Android	B-Application
Package	I-Application
with	O
the	O
file	O
extension	O
apk	B-Application
is	O
the	O
file	O
format	O
used	O
by	O
the	O
Android	B-Application
operating	I-Application
system	I-Application
,	O
and	O
a	O
number	O
of	O
other	O
Android-based	O
operating	O
systems	O
for	O
distribution	O
and	O
installation	O
of	O
mobile	B-Application
apps	I-Application
,	O
mobile	B-Application
games	I-Application
and	O
middleware	B-General_Concept
.	O
</s>
<s>
A	O
file	O
using	O
this	O
format	O
can	O
be	O
built	O
from	O
source	O
code	O
written	O
in	O
either	O
Java	B-Language
or	O
Kotlin	B-Language
.	O
</s>
<s>
APK	B-Application
files	I-Application
can	O
be	O
generated	O
and	O
signed	O
from	O
Android	B-Application
App	I-Application
Bundles	I-Application
.	O
</s>
<s>
APK	B-Application
is	O
analogous	O
to	O
other	O
software	B-Application
packages	I-Application
such	O
as	O
APPX	O
in	O
Microsoft	B-Application
Windows	I-Application
,	O
.app	O
on	O
HAP	O
for	O
HarmonyOS	B-Operating_System
or	O
a	O
Debian	O
package	O
in	O
Debian-based	O
operating	O
systems	O
.	O
</s>
<s>
To	O
make	O
an	O
APK	B-Application
file	I-Application
,	O
a	O
program	O
for	O
Android	B-Application
is	O
first	O
compiled	O
using	O
a	O
tool	O
such	O
as	O
Android	B-Application
Studio	I-Application
or	O
Visual	B-Application
Studio	I-Application
and	O
then	O
all	O
of	O
its	O
parts	O
are	O
packaged	O
into	O
one	O
container	O
file	O
.	O
</s>
<s>
An	O
APK	B-Application
file	I-Application
contains	O
all	O
of	O
a	O
program	O
's	O
code	O
(	O
such	O
as	O
.dex	B-Application
files	O
)	O
,	O
resources	O
,	O
assets	O
,	O
certificates	O
,	O
and	O
manifest	O
file	O
.	O
</s>
<s>
As	O
is	O
the	O
case	O
with	O
many	O
file	O
formats	O
,	O
APK	B-Application
files	I-Application
can	O
have	O
any	O
name	O
needed	O
,	O
but	O
it	O
may	O
be	O
required	O
that	O
the	O
file	O
name	O
ends	O
in	O
the	O
file	O
extension	O
for	O
being	O
recognized	O
as	O
such	O
.	O
</s>
<s>
Most	O
Android	B-Application
implementations	O
allow	O
users	O
to	O
manually	O
install	O
APK	B-Application
files	I-Application
only	O
after	O
they	O
turn	O
on	O
an	O
"	O
Unknown	O
Sources	O
"	O
setting	O
that	O
allows	O
installation	O
from	O
sources	O
other	O
than	O
trusted	O
ones	O
like	O
Google	B-Application
Play	I-Application
.	O
</s>
<s>
Blackberry	O
Limited	O
supported	O
Android	B-Application
4.1	O
Jelly	O
Bean	O
apps	O
and	O
up	O
through	O
Android	B-Application
Runtime	I-Application
to	O
now	O
discontinued	O
Blackberry	B-Application
10	I-Application
through	O
the	O
January	O
2014	O
10.2.1	O
firmware	O
update	O
.	O
</s>
<s>
On	O
June	O
18	O
,	O
2014	O
,	O
BlackBerry	O
announced	O
an	O
official	O
relationship	O
with	O
Amazon.com,	O
which	O
resulted	O
in	O
the	O
10.3	O
update	O
bundling	O
the	O
Amazon	B-Application
Appstore	O
.	O
</s>
<s>
At	O
2015	O
Build	O
,	O
Microsoft	O
had	O
also	O
announced	O
an	O
Android	B-Application
runtime	I-Application
environment	O
for	O
Windows	O
10	O
Mobile	O
known	O
as	O
"	O
Astoria	O
"	O
,	O
which	O
would	O
allow	O
Android	B-Application
apps	O
to	O
run	O
in	O
an	O
emulated	O
environment	O
with	O
minimal	O
changes	O
,	O
and	O
have	O
access	O
to	O
Microsoft	O
platform	O
APIs	O
such	O
as	O
Bing	B-Application
Maps	I-Application
and	O
Xbox	B-Application
Live	I-Application
as	O
nearly	O
drop-in	O
replacements	O
for	O
equivalent	O
Google	B-Application
Mobile	I-Application
Services	I-Application
.	O
</s>
<s>
Google	B-Application
Mobile	I-Application
Services	I-Application
and	O
certain	O
core	O
APIs	O
would	O
not	O
be	O
available	O
,	O
and	O
apps	O
with	O
"	O
deep	O
integration	O
into	O
background	O
tasks	O
"	O
were	O
said	O
to	O
poorly	O
support	O
the	O
environment	O
.	O
</s>
<s>
On	O
February	O
25	O
,	O
2016	O
,	O
after	O
already	O
having	O
delayed	O
it	O
in	O
November	O
2015	O
,	O
Microsoft	O
announced	O
that	O
"	O
Astoria	O
"	O
would	O
be	O
shelved	O
,	O
arguing	O
that	O
it	O
was	O
redundant	O
to	O
the	O
native	O
Windows	O
Bridge	O
toolkit	O
since	O
iOS	O
is	O
already	O
a	O
primary	O
target	O
for	O
mobile	B-Application
app	I-Application
development	O
.	O
</s>
<s>
The	O
company	O
also	O
encouraged	O
use	O
of	O
products	O
from	O
Xamarin	B-Application
(	O
which	O
they	O
had	O
acquired	O
the	O
previous	O
day	O
)	O
for	O
multi-platform	O
app	O
development	O
using	O
C#	B-Application
programming	O
language	O
instead	O
.	O
</s>
<s>
On	O
August	O
9	O
,	O
2019	O
,	O
HarmonyOS	B-Operating_System
1.0	O
for	O
Smart	O
Screen	O
TVs	O
has	O
compatibility	O
for	O
third-party	O
APK	B-Application
apps	O
since	O
there	O
was	O
no	O
SDK	O
for	O
DevEco	B-Operating_System
Studio	I-Operating_System
for	O
native	O
HAP	O
apps	O
until	O
September	O
2020	O
Beta	O
of	O
2.0	O
,	O
as	O
well	O
as	O
watches	O
,	O
phones	O
and	O
tablets	O
by	O
June	O
2021	O
with	O
version	O
2.0	O
.	O
</s>
<s>
At	O
the	O
Windows	B-Application
11	I-Application
announcement	O
event	O
in	O
June	O
2021	O
,	O
Microsoft	O
showcased	O
the	O
new	O
Windows	O
Subsystem	O
for	O
Android	B-Application
(	O
WSA	O
)	O
that	O
will	O
enable	O
support	O
for	O
the	O
Android	B-Application
Open	O
Source	O
Project	O
(	O
AOSP	O
)	O
and	O
will	O
allow	O
users	O
to	O
run	O
Android	B-Application
apps	O
on	O
their	O
Windows	O
desktop	O
.	O
</s>
<s>
Microsoft	O
confirmed	O
users	O
will	O
be	O
able	O
to	O
sideload	O
Android	B-Application
apps	O
onto	O
Windows	O
and	O
that	O
it	O
would	O
be	O
possible	O
to	O
install	O
APK	B-Application
files	I-Application
downloaded	O
from	O
third-party	O
sources	O
.	O
</s>
<s>
Google	O
announced	O
plans	O
in	O
December	O
2021	O
to	O
bring	O
Android	B-Application
games	O
to	O
Windows	O
in	O
2022	O
.	O
</s>
<s>
An	O
APK	B-Application
file	I-Application
is	O
a	O
ZIP	B-General_Concept
archive	I-General_Concept
that	O
usually	O
contains	O
the	O
following	O
files	O
and	O
directories	O
:	O
</s>
<s>
META-INF	B-Language
directory	O
:	O
</s>
<s>
CERT.SF	O
:	O
The	O
list	O
of	O
resources	O
and	O
a	O
SHA-1	B-Algorithm
digest	B-Algorithm
of	O
the	O
corresponding	O
lines	O
in	O
the	O
MANIFEST.MF	O
file	O
;	O
for	O
example	O
:	O
</s>
<s>
lib	O
:	O
the	O
directory	O
containing	O
the	O
compiled	O
code	O
that	O
is	O
platform	O
dependent	O
,	O
for	O
example	O
native	O
libraries	O
that	O
can	O
be	O
loaded	O
through	O
JNI	B-Language
;	O
the	O
directory	O
is	O
split	O
into	O
more	O
directories	O
within	O
it	O
:	O
</s>
<s>
AndroidManifest.xml	O
:	O
An	O
additional	O
Android	B-Application
manifest	O
file	O
,	O
describing	O
the	O
name	O
,	O
version	O
,	O
access	O
rights	O
,	O
referenced	O
library	O
files	O
for	O
the	O
application	O
.	O
</s>
<s>
This	O
file	O
may	O
be	O
in	O
Android	B-Application
binary	B-Protocol
XML	I-Protocol
that	O
can	O
be	O
converted	O
into	O
human-readable	O
plaintext	O
XML	O
with	O
tools	O
such	O
as	O
AXMLPrinter2	O
,	O
Apktool	O
M	O
,	O
or	O
Androguard	O
.	O
</s>
<s>
classes.dex	O
:	O
The	O
classes	O
compiled	O
in	O
the	O
dex	B-Application
file	I-Application
format	I-Application
executed	O
by	O
Android	B-Application
Runtime	I-Application
(	O
or	O
by	O
Dalvik	B-Application
virtual	I-Application
machine	I-Application
used	O
in	O
Android	B-Application
4.4	I-Application
KitKat	I-Application
)	O
.	O
</s>
<s>
resources.arsc	O
:	O
a	O
file	O
containing	O
precompiled	O
resources	O
,	O
such	O
as	O
binary	B-Protocol
XML	I-Protocol
for	O
example	O
.	O
</s>
