<s>
The	O
functionality	O
of	O
mobile	B-Application
devices	I-Application
running	O
the	O
Android	B-Application
operating	I-Application
system	I-Application
,	O
the	O
most	O
used	O
mobile	O
operating	B-General_Concept
system	I-General_Concept
globally	O
,	O
can	O
be	O
extended	O
using	O
"	O
apps	B-Application
"	O
specialized	O
software	O
designed	B-Application
to	O
offer	O
users	O
the	O
means	O
to	O
use	O
their	O
devices	O
for	O
certain	O
additional	O
purposes	O
.	O
</s>
<s>
Such	O
apps	B-Application
are	O
compiled	O
in	O
the	O
Android-native	O
APK	B-Application
file	I-Application
format	I-Application
which	O
allows	O
easy	O
redistribution	O
of	O
apps	B-Application
to	O
end-users	O
.	O
</s>
<s>
Most	O
apps	B-Application
are	O
distributed	O
through	O
Google	B-Application
's	I-Application
Play	B-Application
Store	I-Application
but	O
many	O
alternative	O
software	O
repositories	O
,	O
or	O
app	B-Application
stores	I-Application
,	O
exist	O
.	O
</s>
<s>
Alternative	O
app	B-Application
stores	I-Application
use	O
the	O
"	O
Unknown	O
Sources	O
"	O
option	O
of	O
Android	B-Application
devices	O
to	O
install	O
APK	B-Application
files	I-Application
directly	O
via	O
the	O
Android	B-Application
Package	I-Application
Manager	O
.	O
</s>
<s>
The	B-Application
Google	I-Application
Play	B-Application
Store	I-Application
(	O
originally	O
the	O
Android	B-Application
Market	I-Application
)	O
,	O
operated	O
and	O
developed	O
by	O
Google	B-Application
,	O
serves	O
as	O
the	O
official	O
app	B-Application
store	I-Application
for	O
the	O
Android	B-Application
,	O
allowing	O
users	O
to	O
download	O
apps	B-Application
developed	O
with	O
the	O
Android	B-Application
software	I-Application
development	I-Application
kit	O
(	O
SDK	O
)	O
and	O
published	O
through	O
Google	B-Application
.	I-Application
</s>
<s>
The	O
store	O
offers	O
both	O
free	O
and	O
paid	O
apps	B-Application
.	O
</s>
<s>
Apps	B-Application
exploiting	O
hardware	O
capabilities	O
of	O
a	O
device	O
can	O
be	O
targeted	O
to	O
users	O
of	O
devices	O
with	O
specific	O
hardware	O
components	O
,	O
such	O
as	O
a	O
motion	O
sensor	O
(	O
for	O
motion-dependent	O
games	O
)	O
or	O
a	O
front-facing	O
camera	O
(	O
for	O
online	O
video	O
calling	O
)	O
.	O
</s>
<s>
The	B-Application
Google	I-Application
Play	B-Application
store	I-Application
had	O
over	O
50	O
billion	O
app	O
downloads	O
in	O
2013	O
and	O
has	O
reached	O
over	O
2.96	O
million	O
apps	B-Application
published	O
in	O
2020	O
.	O
</s>
<s>
Although	O
bundled	O
with	O
most	O
Android	B-Application
devices	O
,	O
the	O
Play	B-Application
Store	I-Application
is	O
only	O
available	O
on	O
devices	O
that	O
are	O
certified	O
within	O
the	O
"	O
Android	B-Application
Compatibility	O
Program	O
"	O
.	O
</s>
<s>
modified	O
versions	O
of	O
Android	B-Application
,	O
are	O
not	O
allowed	O
to	O
bundle	O
Google	B-Application
apps	B-Application
,	O
including	O
the	O
Play	B-Application
Store	I-Application
,	O
with	O
their	O
software	O
.	O
</s>
<s>
Compatibility	O
can	O
be	O
restored	O
by	O
installing	O
the	B-Application
Google	I-Application
apps	B-Application
from	O
another	O
source	O
,	O
such	O
as	O
OpenGApps	O
,	O
or	O
using	O
alternative	O
app	B-Application
stores	I-Application
.	O
</s>
<s>
In	O
addition	O
to	O
some	O
manufacturers	O
not	O
creating	O
certified	O
compatible	O
versions	O
of	O
Android	B-Application
,	O
some	O
manufacturers	O
have	O
decided	O
to	O
bundle	O
their	O
own	O
app	B-Application
stores	I-Application
,	O
either	O
in	O
addition	O
to	O
the	O
Play	B-Application
Store	I-Application
or	O
as	O
a	O
replacement	O
.	O
</s>
<s>
Such	O
app	B-Application
stores	I-Application
include	O
:	O
</s>
<s>
Samsung	B-Application
Galaxy	I-Application
Store	I-Application
,	O
which	O
is	O
installed	O
on	O
Samsung	B-Application
mobile	B-Application
devices	I-Application
alongside	O
the	O
Play	B-Application
Store	I-Application
.	O
</s>
<s>
Amazon	B-Application
Appstore	O
,	O
which	O
is	O
installed	O
instead	O
of	O
the	O
Play	B-Application
Store	I-Application
on	O
Amazon	B-Application
's	I-Application
Fire	B-Application
Phone	I-Application
and	O
Kindle	B-Application
Fire	I-Application
.	O
</s>
<s>
The	O
Amazon	B-Application
Appstore	O
can	O
also	O
be	O
installed	O
on	O
other	O
Android	B-Application
devices	O
by	O
downloading	O
it	O
from	O
the	O
Amazon	B-Application
website	O
.	O
</s>
<s>
This	O
will	O
also	O
be	O
the	O
default	O
way	O
to	O
install	O
Android	B-Application
apps	B-Application
on	O
Windows	B-Application
11	I-Application
.	O
</s>
<s>
Huawei	B-Application
AppGallery	I-Application
,	O
which	O
is	O
installed	O
on	O
Huawei	O
mobile	B-Application
devices	I-Application
.	O
</s>
<s>
After	O
Google	B-Application
Mobile	I-Application
Services	I-Application
ban	O
,	O
AppGallery	B-Application
is	O
sole	O
app	O
distribution	O
on	O
Huawei	O
's	O
phones	O
.	O
</s>
<s>
App	B-Application
stores	I-Application
that	O
do	O
not	O
rely	O
on	O
pre-installation	O
by	O
the	O
manufacturer	O
are	O
an	O
alternate	O
option	O
for	O
finding	O
Android	B-Application
applications	I-Application
.	O
</s>
<s>
Apps	B-Application
offered	O
through	O
third-party	O
app	B-Application
stores	I-Application
or	O
websites	O
,	O
created	O
by	O
parties	O
not	O
affiliated	O
with	O
the	O
device	O
or	O
operating	B-General_Concept
system	I-General_Concept
(	O
OS	O
)	O
,	O
are	O
also	O
third-party	O
apps	B-Application
.	O
</s>
<s>
This	O
form	O
of	O
app	B-Application
store	I-Application
is	O
often	O
used	O
by	O
web	B-Operating_System
developers	I-Operating_System
to	O
distribute	O
apps	B-Application
that	O
are	O
not	O
allowed	O
in	O
the	B-Application
Google	I-Application
Play	B-Application
Store	I-Application
;	O
this	O
may	O
be	O
due	O
to	O
an	O
app	O
allowing	O
users	O
wider	O
access	O
to	O
the	O
app-system	O
,	O
or	O
offering	O
apps	B-Application
for	O
"	O
niche	O
users	O
"	O
who	O
choose	O
to	O
use	O
only	O
free	B-License
and	I-License
open-source	I-License
software	I-License
(	O
F-Droid	B-Application
)	O
or	O
prefer	O
to	O
play	O
indie	O
games	O
(	O
Itch.io	O
)	O
.	O
</s>
<s>
Moreover	O
,	O
there	O
are	O
alternative	O
stores	O
that	O
serve	O
to	O
distribute	O
"	O
hacked	O
"	O
versions	O
of	O
paid	O
apps	B-Application
,	O
for	O
no	O
cost	O
.	O
</s>
<s>
There	O
are	O
also	O
proxy	O
app	B-Application
stores	I-Application
that	O
act	O
as	O
a	O
client	O
for	O
Google	B-Application
Play	I-Application
store	I-Application
,	O
such	O
as	O
Aurora	O
Store	O
.	O
</s>
