<s>
f.lux	B-Operating_System
(	O
pronounced	O
"	O
flux	O
"	O
)	O
is	O
a	O
cross-platform	B-Operating_System
computer	B-Application
program	I-Application
that	O
adjusts	O
a	O
display	B-Device
's	I-Device
color	O
temperature	O
according	O
to	O
location	O
and	O
time	O
of	O
day	O
,	O
offering	O
functional	O
respite	O
for	O
the	O
eyes	O
.	O
</s>
<s>
The	O
program	O
then	O
automatically	O
calibrates	O
the	O
device	O
display	B-Device
's	I-Device
color	O
temperature	O
to	O
account	O
for	O
time	O
of	O
day	O
,	O
based	O
on	O
sunrise	B-Application
and	O
sunset	B-Application
at	O
the	O
chosen	O
location	O
.	O
</s>
<s>
At	O
sunset	B-Application
,	O
it	O
will	O
gradually	O
change	O
the	O
color	O
temperature	O
to	O
a	O
warmer	O
color	O
and	O
restore	O
the	O
original	O
color	O
at	O
sunrise	B-Application
.	O
</s>
<s>
f.lux	B-Operating_System
offers	O
a	O
variety	O
of	O
color	O
profiles	O
and	O
pre-defined	O
temperature	O
values	O
,	O
modifying	O
program	O
behaviour	O
for	O
specific	O
programs	O
or	O
activities	O
;	O
including	O
a	O
mode	O
for	O
film	O
watching	O
,	O
decreasing	O
red	O
tinge	O
(	O
for	O
2.5	O
hours	O
)	O
,	O
and	O
a	O
darkroom	O
mode	O
that	O
does	O
not	O
affect	O
night-adapted	O
vision	O
.	O
</s>
<s>
Times	O
can	O
be	O
inverted	O
on	O
f.lux	B-Operating_System
for	O
PC	O
to	O
provide	O
warm	O
lighting	O
during	O
the	O
daytime	O
(	O
for	O
people	O
who	O
work	O
at	O
night	O
)	O
.	O
</s>
<s>
The	O
program	O
can	O
control	O
Philips	O
Hue	O
LED	O
lighting	O
,	O
so	O
that	O
the	O
color	O
temperature	O
of	O
house	O
lights	O
follows	O
f.lux	B-Operating_System
'	O
s	O
settings	O
.	O
</s>
<s>
The	O
program	O
is	O
available	O
for	O
Microsoft	B-Application
Windows	I-Application
,	O
macOS	B-Application
and	O
Linux	B-Application
(	O
except	O
for	O
Ubuntu	O
18.04	O
LTS	O
)	O
.	O
</s>
<s>
It	O
is	O
also	O
available	O
for	O
Apple	O
iOS	B-Application
devices	O
,	O
although	O
it	O
requires	O
the	O
device	O
to	O
be	O
jailbroken	B-Application
.	O
</s>
<s>
Apple	O
has	O
not	O
allowed	O
the	O
application	O
in	O
its	O
App	B-Application
Store	I-Application
due	O
to	O
its	O
use	O
of	O
restricted	O
developer	O
tools	O
.	O
</s>
<s>
The	O
developer	O
briefly	O
hosted	O
an	O
Xcode	B-Operating_System
project	O
on	O
GitHub	B-Application
,	O
allowing	O
iOS	B-Operating_System
9	I-Operating_System
users	O
to	O
sideload	B-Protocol
the	O
application	O
onto	O
their	O
devices	O
,	O
but	O
retracted	O
it	O
at	O
the	O
request	O
of	O
Apple	O
.	O
</s>
<s>
Following	O
Apple	O
's	O
announcement	O
of	O
a	O
similar	O
function	O
,	O
called	O
Night	B-Operating_System
Shift	I-Operating_System
,	O
in	O
iOS	B-Operating_System
9.3	I-Operating_System
,	O
the	O
developer	O
called	O
upon	O
Apple	O
to	O
provide	O
developer	O
tools	O
and	O
to	O
allow	O
their	O
application	O
into	O
the	O
App	B-Application
Store	I-Application
.	O
</s>
<s>
A	O
preview	O
version	O
for	O
Google	B-Application
's	I-Application
Android	I-Application
system	O
is	O
available	O
.	O
</s>
<s>
Reducing	O
exposure	O
to	O
bright	O
(	O
1000	O
lux	B-Application
)	O
blue	O
lights	O
at	O
night	O
time	O
was	O
linked	O
to	O
increased	O
melatonin	O
secretion	O
in	O
a	O
1996	O
study	O
but	O
a	O
2018	O
study	O
showed	O
that	O
changing	O
the	O
spectral	O
composition	O
of	O
self-luminous	O
displays	O
without	O
changing	O
their	O
brightness	O
settings	O
may	O
be	O
insufficient	O
for	O
preventing	O
impacts	O
on	O
melatonin	O
suppression	O
.	O
</s>
<s>
f.lux	B-Operating_System
proponents	O
hypothesize	O
that	O
altering	O
the	O
color	O
temperature	O
of	O
a	O
display	O
to	O
reduce	O
the	O
prominence	O
of	O
white	O
–	O
blue	O
light	O
at	O
night	O
will	O
improve	O
the	O
effectiveness	O
of	O
sleep	O
.	O
</s>
<s>
Although	O
the	O
developer	O
provides	O
a	O
list	O
of	O
relevant	O
research	O
on	O
their	O
website	O
,	O
the	O
program	O
itself	O
has	O
not	O
been	O
scientifically	O
tested	O
to	O
determine	O
its	O
efficacy	O
,	O
and	O
the	O
equivalent	O
Apple	O
program	O
,	O
Night	B-Operating_System
Shift	I-Operating_System
,	O
was	O
shown	O
to	O
have	O
no	O
effect	O
on	O
sleep	O
outcomes	O
(	O
sleep	O
latency	O
,	O
duration	O
,	O
efficiency	O
and	O
wake	O
after	O
sleep	O
onset	O
)	O
in	O
a	O
2021	O
study	O
on	O
167	O
college	O
undergraduates	O
.	O
</s>
<s>
f.lux	B-Operating_System
has	O
been	O
widely	O
and	O
positively	O
reviewed	O
by	O
technology	O
journalists	O
,	O
bloggers	O
,	O
and	O
users	O
.	O
</s>
