<s>
A	O
light-on-dark	B-General_Concept
color	I-General_Concept
scheme	I-General_Concept
—	O
also	O
called	O
black	O
mode	O
,	O
dark	B-General_Concept
mode	I-General_Concept
,	O
dark	B-General_Concept
theme	I-General_Concept
,	O
night	B-General_Concept
mode	I-General_Concept
,	O
or	O
lights-out	O
(	O
mode	O
)	O
—	O
is	O
a	O
color	O
scheme	O
that	O
uses	O
light-colored	O
text	O
,	O
icons	O
,	O
and	O
graphical	O
user	B-Application
interface	I-Application
elements	O
on	O
a	O
dark	O
background	O
.	O
</s>
<s>
It	O
is	O
often	O
discussed	O
in	O
terms	O
of	O
computer	O
user	B-Application
interface	I-Application
design	O
and	O
web	O
design	O
.	O
</s>
<s>
Many	O
modern	O
websites	O
and	O
operating	O
systems	O
offer	O
the	O
user	O
an	O
optional	O
light-on-dark	B-General_Concept
display	O
mode	O
.	O
</s>
<s>
Some	O
users	O
find	O
dark	B-General_Concept
mode	I-General_Concept
displays	O
more	O
visually	O
appealing	O
,	O
and	O
claim	O
that	O
it	O
can	O
reduce	O
eye	O
strain	O
.	O
</s>
<s>
Displaying	O
white	O
at	O
full	O
brightness	O
uses	O
roughly	O
six	O
times	O
as	O
much	O
power	O
as	O
pure	O
black	O
on	O
a	O
2016	O
Google	B-Device
Pixel	I-Device
,	O
which	O
has	O
an	O
OLED	B-Device
display	I-Device
.	O
</s>
<s>
Most	O
modern	O
operating	O
systems	O
support	O
an	O
optional	O
light-on-dark	B-General_Concept
color	I-General_Concept
scheme	I-General_Concept
.	O
</s>
<s>
With	O
the	O
introduction	O
of	O
computer	O
screens	O
,	O
originally	O
user	B-Application
interfaces	I-Application
were	O
formed	O
on	O
cathode-ray	B-Device
tubes	I-Device
(	O
CRTs	O
)	O
like	O
those	O
used	O
for	O
oscillographs	O
or	O
oscilloscopes	O
.	O
</s>
<s>
The	O
opposite	O
color	O
set	O
,	O
a	O
dark-on-light	B-General_Concept
color	I-General_Concept
scheme	I-General_Concept
,	O
was	O
originally	O
introduced	O
in	O
WYSIWYG	B-Application
word	B-General_Concept
processors	I-General_Concept
to	O
simulate	O
ink	O
on	O
paper	O
,	O
and	O
became	O
the	O
norm	O
.	O
</s>
<s>
In	O
2018	O
,	O
Apple	O
followed	O
in	O
macOS	B-Device
Mojave	I-Device
.	O
</s>
<s>
In	O
September	O
2019	O
,	O
iOS	B-Operating_System
13	I-Operating_System
and	O
Android	B-Application
10	I-Application
both	O
introduced	O
dark	B-General_Concept
modes	I-General_Concept
.	O
</s>
<s>
Firefox	B-Application
and	O
Chromium	B-Language
have	O
optional	O
dark	B-General_Concept
theme	I-General_Concept
for	O
all	O
internal	O
screens	O
.	O
</s>
<s>
It	O
will	O
also	O
be	O
possible	O
for	O
third-party	O
developers	O
to	O
implement	O
their	O
own	O
dark	B-General_Concept
themes	I-General_Concept
.	O
</s>
<s>
In	O
2019	O
,	O
a	O
"	O
prefers-color-scheme	O
"	O
option	O
was	O
created	O
for	O
front-end	O
web	O
developers	O
,	O
being	O
a	O
CSS	B-Language
property	O
that	O
signals	O
a	O
user	O
's	O
choice	O
for	O
their	O
system	O
to	O
use	O
a	O
light	O
or	O
dark	O
color	O
theme	O
.	O
</s>
<s>
Light	B-General_Concept
on	I-General_Concept
dark	I-General_Concept
color	O
schemes	O
require	O
less	O
energy	O
to	O
display	O
on	O
OLED	B-Device
displays	I-Device
.	O
</s>
<s>
While	O
an	O
OLED	B-Device
will	O
consume	O
around	O
40%	O
of	O
the	O
power	O
of	O
an	O
LCD	O
displaying	O
an	O
image	O
that	O
is	O
primarily	O
black	O
,	O
it	O
can	O
use	O
more	O
than	O
three	O
times	O
as	O
much	O
power	O
to	O
display	O
an	O
image	O
with	O
a	O
white	O
background	O
,	O
such	O
as	O
a	O
document	O
or	O
web	O
site	O
.	O
</s>
<s>
This	O
can	O
lead	O
to	O
reduced	O
battery	O
life	O
and	O
energy	O
usage	O
unless	O
a	O
light-on-dark	B-General_Concept
color	I-General_Concept
scheme	I-General_Concept
is	O
used	O
.	O
</s>
<s>
The	O
energy	O
savings	O
that	O
can	O
be	O
achieved	O
using	O
a	O
light-on-dark	B-General_Concept
color	I-General_Concept
scheme	I-General_Concept
are	O
because	O
of	O
how	O
OLED	B-Device
screens	I-Device
work	O
:	O
in	O
an	O
OLED	B-Device
screen	I-Device
,	O
each	O
subpixel	O
generates	O
its	O
own	O
light	O
and	O
it	O
only	O
consumes	O
power	O
when	O
generating	O
light	O
.	O
</s>
<s>
"	O
AMOLED	B-Algorithm
Black	O
"	O
color	O
schemes	O
(	O
that	O
use	O
pure	O
black	O
instead	O
of	O
dark	O
gray	O
)	O
do	O
not	O
necessarily	O
save	O
more	O
energy	O
than	O
other	O
light-on-dark	B-General_Concept
color	O
schemes	O
that	O
use	O
dark	O
gray	O
instead	O
of	O
black	O
,	O
as	O
the	O
power	O
consumption	O
on	O
an	O
AMOLED	B-Algorithm
screen	O
decreases	O
proportionately	O
to	O
the	O
average	O
brightness	O
of	O
the	O
displayed	O
pixels	O
.	O
</s>
<s>
Although	O
it	O
is	O
true	O
that	O
AMOLED	B-Algorithm
black	O
does	O
save	O
more	O
energy	O
than	O
dark	O
gray	O
,	O
the	O
additional	O
energy	O
savings	O
are	O
often	O
negligible	O
;	O
AMOLED	B-Algorithm
black	O
will	O
only	O
give	O
an	O
additional	O
energy	O
saving	O
of	O
less	O
than	O
1%	O
,	O
for	O
instance	O
,	O
over	O
the	O
dark	O
gray	O
that	O
's	O
used	O
in	O
the	O
dark	B-General_Concept
theme	I-General_Concept
for	O
Google	B-Application
's	I-Application
official	O
Android	O
apps	O
.	O
</s>
<s>
In	O
November	O
2018	O
,	O
Google	B-Application
confirmed	O
that	O
dark	B-General_Concept
mode	I-General_Concept
on	O
Android	O
saved	O
battery	O
life	O
.	O
</s>
<s>
The	O
caveat	O
is	O
that	O
most	O
pages	O
on	O
the	O
web	O
are	O
designed	O
for	O
white	O
backgrounds	O
;	O
GIF	O
and	O
PNG	O
images	O
with	O
a	O
transparency	O
bit	O
instead	O
of	O
alpha	B-Algorithm
channels	I-Algorithm
tend	O
to	O
show	O
up	O
with	O
choppy	O
outlines	O
,	O
as	O
well	O
as	O
causing	O
problems	O
with	O
other	O
graphical	O
elements	O
.	O
</s>
<s>
There	O
is	O
a	O
prefers-color-scheme	O
media	O
feature	O
on	O
CSS	B-Language
,	O
to	O
detect	O
if	O
the	O
user	O
has	O
requested	O
light	O
or	O
dark	O
color	O
scheme	O
and	O
serve	O
the	O
requested	O
color	O
scheme	O
.	O
</s>
<s>
It	O
can	O
be	O
indicated	O
from	O
the	O
user	O
's	O
operating	O
system	O
preference	O
or	O
a	O
user	B-Protocol
agent	I-Protocol
.	O
</s>
<s>
CSS	B-Language
example	O
:	O
</s>
