<s>
Google	B-Application
PageSpeed	B-Application
is	O
a	O
family	O
of	O
tools	O
by	O
Google	B-Application
Inc	I-Application
,	O
designed	O
to	O
help	O
a	O
website	O
's	O
performance	O
optimizations	O
.	O
</s>
<s>
It	O
was	O
introduced	O
at	O
Developer	B-Application
Conference	I-Application
in	O
2010	O
.	O
</s>
<s>
There	O
are	O
four	O
main	O
components	O
of	O
PageSpeed	B-Application
family	O
tools	O
:	O
PageSpeed	B-Application
Module	O
,	O
consisting	O
of	O
mod	O
PageSpeed	B-Application
for	O
the	O
Apache	B-Application
HTTP	I-Application
Server	I-Application
and	O
ngx	O
PageSpeed	B-Application
for	O
the	O
Nginx	B-Operating_System
,	O
PageSpeed	B-Application
Insights	O
,	O
PageSpeed	B-Application
Service	O
,	O
and	O
PageSpeed	B-Application
Chrome	O
DevTools	B-Application
extension	O
.	O
</s>
<s>
All	O
of	O
these	O
components	O
are	O
built	O
to	O
identify	O
the	O
faults	O
in	O
a	O
website	O
's	O
compliance	O
with	O
Google	B-Application
's	I-Application
Web	O
Performance	O
Best	O
Practices	O
,	O
as	O
well	O
as	O
automate	O
the	O
adjustment	O
process	O
.	O
</s>
<s>
The	O
PageSpeed	B-Application
Modules	O
are	O
the	O
open-source	B-License
Apache	B-Application
HTTP	I-Application
Server	I-Application
or	O
Nginx	B-Operating_System
webservers	B-Application
modules	O
,	O
which	O
automatically	O
apply	O
chosen	O
filters	O
to	O
pages	O
and	O
associated	O
assets	O
,	O
such	O
as	O
stylesheets	B-Language
,	O
JavaScript	B-Language
,	O
and	O
HTML	B-Language
files	I-Language
,	O
as	O
well	O
as	O
to	O
images	O
and	O
website	B-Protocol
cache	I-Protocol
requirements	O
.	O
</s>
<s>
Each	O
of	O
40+	O
filters	O
corresponds	O
to	O
one	O
of	O
Google	B-Application
's	I-Application
web	O
performance	O
best	O
practices	O
rules	O
.	O
</s>
<s>
Since	O
PageSpeed	B-Application
module	O
is	O
an	O
open	B-License
source	I-License
library	O
,	O
it	O
is	O
frequently	O
updated	O
by	O
numerous	O
developers	O
from	O
all	O
over	O
the	O
world	O
and	O
can	O
be	O
deployed	O
by	O
any	O
individual	O
sites	O
,	O
hosting	O
providers	O
,	O
or	O
CDNs	B-Operating_System
.	O
</s>
<s>
Other	O
servers	O
that	O
offer	O
a	O
PageSpeed	B-Application
optimization	O
module	O
based	O
on	O
Google	B-Application
's	I-Application
Page	O
Speed	O
SDK	O
:	O
</s>
<s>
Pagespeed	B-Application
module	O
filters	O
are	O
settings	O
,	O
based	O
on	O
which	O
a	O
webpage	O
optimization	O
rule	O
is	O
applied	O
.	O
</s>
<s>
Stylesheets	B-Language
optimizations	O
;	O
</s>
<s>
Javascript	B-Language
files	I-Language
optimizations	O
;	O
</s>
<s>
HTML	B-Language
optimizations	O
;	O
</s>
<s>
These	O
filters	O
change	O
CSS	B-Language
files	O
to	O
optimized	O
versions	O
through	O
making	O
them	O
smaller	O
,	O
combining	O
several	O
into	O
one	O
or	O
extending	O
cache	O
lifetime	O
:	O
</s>
<s>
Filter	O
Name	O
Description	O
Combine	O
CSS	B-Language
If	O
a	O
page	O
requires	O
several	O
stylesheets	B-Language
,	O
this	O
filter	O
combines	O
them	O
into	O
one	O
stylesheet	B-Language
,	O
decreasing	O
the	O
number	O
of	O
requests	O
to	O
a	O
web	B-Application
server	I-Application
Extend	O
Cache	O
for	O
Stylesheets	B-Language
Increases	O
the	O
time	O
that	O
cached	O
CSS	B-Language
files	O
are	O
to	O
be	O
kept	O
in	O
local	O
storage	O
,	O
preventing	O
extra	O
requests	O
and	O
data	O
loading	O
upon	O
a	O
user	O
's	O
return	O
to	O
the	O
same	O
webpage	O
Flatten	O
CSS	B-Language
Imports	O
Replaces	O
all	O
“	O
@import	O
”	O
rules	O
with	O
the	O
contents	O
of	O
imported	O
files	O
,	O
if	O
the	O
size	O
of	O
the	O
affected	O
stylesheet	B-Language
files	I-Language
is	O
less	O
than	O
the	O
number	O
of	O
pre-determined	O
bytes	O
set	O
by	O
the	O
sub-filter	O
“	O
CssFlattenMaxBytes	O
”	O
.	O
</s>
<s>
This	O
optimization	O
is	O
designed	O
for	O
reducing	O
the	O
number	O
of	O
requests	O
by	O
the	O
web	B-Application
browser	I-Application
Inline	O
@import	O
To	O
Link	O
Transforms	O
“	O
@import	O
”	O
rules	O
into	O
corresponding	O
“”	O
tags	B-General_Concept
.	O
</s>
<s>
Mostly	O
is	O
used	O
for	O
proper	O
work	O
of	O
later	O
applied	O
filters	O
Inline	O
CSS	B-Language
Inserts	O
small	O
external	O
stylesheet	O
files’	O
content	O
directly	O
into	O
HTML	B-Language
document	I-Language
,	O
therefore	O
reducing	O
number	O
of	O
requests	O
.	O
</s>
<s>
This	O
filter	O
is	O
applied	O
only	O
to	O
stylesheets	B-Language
that	O
are	O
smaller	O
than	O
a	O
size	O
set	O
by	O
sub-filter	O
“	O
CssInlineMaxBytes	O
”	O
Inline	O
Google	B-Application
Fonts	I-Application
API	O
CSS	B-Language
Inserts	O
any	O
stylesheets	B-Language
,	O
used	O
by	O
Google	B-Application
Font	I-Application
API	I-Application
,	O
if	O
they	O
are	O
smaller	O
than	O
a	O
value	O
,	O
which	O
is	O
set	O
by	O
sub-filter	O
“	O
CssInlineMaxBytes	O
”	O
Move	O
CSS	B-Language
Above	O
Scripts	O
Rearranges	O
the	O
order	O
of	O
loading	O
stylesheets	B-Language
and	O
javascript	B-Language
files	I-Language
,	O
assuring	O
that	O
scripts	O
are	O
not	O
blocking	O
CSS	B-Language
resources	O
.	O
</s>
<s>
Improves	O
rendering	O
of	O
a	O
webpage	O
,	O
leading	O
to	O
shorter	O
loading	O
times	O
Move	O
CSS	B-Language
to	O
Head	O
Places	O
stylesheets	B-Language
inclusion	O
before	O
any	O
<body>	O
elements	O
are	O
introduced	O
,	O
which	O
decreases	O
the	O
loading	O
time	O
by	O
eliminating	O
re-flows	O
of	O
a	O
webpage	O
Outline	O
CSS	B-Language
Experimental	O
filter	O
which	O
puts	O
inlined	O
CSS	B-Language
rules	O
on	O
an	O
external	O
resource	O
.	O
</s>
<s>
This	O
filter	O
will	O
try	O
to	O
outline	O
only	O
stylesheets	B-Language
bigger	O
than	O
set	O
by	O
sub-filter	O
“	O
CssOutlineMinBytes	O
”	O
Prioritize	O
Critical	O
CSS	B-Language
Replaces	O
stylesheets	B-Language
with	O
inlined	O
CSS	B-Language
rules	O
,	O
containing	O
only	O
necessary	O
rules	O
for	O
initial	O
viewport	O
,	O
and	O
defers	O
the	O
rest	O
of	O
CSS	B-Language
rules	O
to	O
be	O
loaded	O
after	O
the	O
page	O
is	O
fully	O
loaded	O
Rewrite	O
CSS	B-Language
Allows	O
other	O
stylesheet	B-Language
and	O
image	O
related	O
filters	O
to	O
be	O
applied	O
to	O
local	O
stylesheets	B-Language
.	O
</s>
<s>
Additionally	O
,	O
this	O
filter	O
minifies	O
all	O
CSS	B-Language
.	O
</s>
<s>
These	O
filters	O
are	O
applied	O
to	O
Javascript	B-Language
files	I-Language
,	O
re-referring	O
them	O
to	O
optimized	O
files	O
:	O
</s>
<s>
Filter	O
Name	O
Description	O
Canonicalize	O
Javascript	B-Language
libraries	O
Replaces	O
popular	O
javascript	B-Language
libraries	O
with	O
remote	O
latest	O
free	O
versions	O
,	O
from	O
Google	B-Application
Hosted	O
Libraries	O
by	O
default	O
.	O
</s>
<s>
This	O
potentially	O
decreases	O
the	O
number	O
of	O
requests	O
to	O
servers	O
in	O
the	O
future	O
,	O
since	O
these	O
libraries	O
might	O
be	O
in	O
user	O
's	O
browser	B-Protocol
cache	I-Protocol
from	O
any	O
other	O
websites	O
Combine	O
Javascript	B-Language
Combines	O
multiple	O
javascript	B-Language
files	I-Language
into	O
one	O
,	O
therefore	O
decreasing	O
total	O
number	O
of	O
requests	O
by	O
a	O
browser	B-Application
Defer	O
Javascript	B-Language
Postpones	O
loading	O
and	O
executing	O
javascript	B-Language
files	I-Language
until	O
a	O
page	O
is	O
loaded	O
.	O
</s>
<s>
This	O
ensures	O
that	O
the	O
loading	O
of	O
visible	O
content	O
is	O
not	O
interrupted	O
Extend	O
Cache	O
for	O
Javascript	B-Language
Increases	O
the	O
period	O
of	O
time	O
in	O
which	O
cached	O
javascript	B-Language
files	I-Language
are	O
to	O
be	O
kept	O
in	O
local	O
storage	O
,	O
preventing	O
extra	O
requests	O
and	O
data	O
loading	O
upon	O
user	O
return	O
to	O
the	O
same	O
webpage	O
Include	O
Javascript	B-Language
Source	O
Maps	O
Creates	O
the	O
“	O
map	O
”	O
between	O
minified	O
and	O
original	O
javascript	B-Language
files	I-Language
for	O
improved	O
readability	O
during	O
the	O
debugging	O
process	O
Inline	O
Javascript	B-Language
Inserts	O
small	O
external	O
javascript	B-Language
files’	O
content	O
directly	O
into	O
HTML	B-Language
document	I-Language
,	O
therefore	O
reducing	O
the	O
number	O
of	O
requests	O
.	O
</s>
<s>
This	O
filter	O
is	O
applied	O
only	O
to	O
javascript	B-Language
files	I-Language
smaller	O
than	O
the	O
size	O
set	O
by	O
sub-filter	O
“	O
JsInlineMaxBytes	O
”	O
Minify	O
External	O
Javascript	B-Language
,	O
Minify	O
Internal	O
Javascript	B-Language
Removes	O
all	O
comments	O
,	O
whitespaces	O
,	O
redundant	O
and	O
obsolete	O
rules	O
,	O
which	O
reduces	O
the	O
total	O
number	O
of	O
bytes	O
loaded	O
Outline	O
Javascript	B-Language
Experimental	O
filter	O
which	O
puts	O
inlined	O
javascript	B-Language
on	O
an	O
external	O
resource	O
.	O
</s>
<s>
Filter	O
Name	O
Description	O
Deduplicate	O
Inlined	B-Protocol
Images	I-Protocol
Eliminates	O
repetitive	O
data	O
loading	O
of	O
the	O
same	O
inlined	B-Protocol
images	I-Protocol
,	O
improving	O
the	O
number	O
of	O
requests	O
and	O
transfer	O
size	O
Extend	O
Cache	O
for	O
Images	O
Increases	O
the	O
time	O
that	O
cached	O
images	O
are	O
to	O
be	O
kept	O
in	O
local	O
storage	O
,	O
preventing	O
extra	O
requests	O
and	O
data	O
loading	O
upon	O
user	O
return	O
to	O
the	O
same	O
webpage	O
Inline	O
Preview	O
Images	O
Generates	O
low	O
quality	O
versions	O
of	O
a	O
number	O
of	O
inlined	B-Protocol
images	I-Protocol
set	O
by	O
sub-filter	O
“	O
MaxInlinedPreviewImagesIndex	O
”	O
,	O
unless	O
the	O
size	O
of	O
the	O
images	O
is	O
higher	O
than	O
the	O
value	O
set	O
by	O
sub-filter	O
“	O
MinImageSizeLowResolutionBytes	O
”	O
,	O
improving	O
user	O
experience	O
.	O
</s>
<s>
After	O
the	O
page	O
is	O
fully	O
loaded	O
,	O
images	O
are	O
switched	O
to	O
higher	O
quality	O
Lazyload	O
Images	O
Postpones	B-General_Concept
loading	I-General_Concept
of	I-General_Concept
images	I-General_Concept
,	O
which	O
are	O
not	O
in	O
a	O
user	O
's	O
initial	O
viewport	O
,	O
decreasing	O
the	O
number	O
of	O
browser	B-Application
's	O
requests	O
Inline	B-Protocol
Images	I-Protocol
Provides	O
a	O
way	O
to	O
include	O
image	O
data	O
into	O
actual	O
webpage	O
code	O
as	O
if	O
an	O
image	O
was	O
an	O
external	O
resource	O
,	O
eliminating	O
extra	O
connections	O
to	O
retrieve	O
image	O
data	O
Convert	O
GIFs	O
to	O
PNG	O
Loselessly	B-Algorithm
converts	O
non-animated	O
gifs	O
into	O
pngs	O
,	O
decreasing	O
data	O
size	O
Convert	O
JPEGs	O
to	O
Progressive	O
JPEGs	O
Transforms	O
automatically	O
generated	O
larger	O
non-progressive	O
JPEG	O
images	O
into	O
smaller	O
progressive	O
type	O
Recompress	O
JPEGs	O
Recompresses	O
automatically	O
generated	O
JPEG	O
images	O
if	O
their	O
original	O
compression	B-General_Concept
quality	I-General_Concept
was	O
higher	O
than	O
value	O
,	O
set	O
by	O
sub-filters	O
“	O
ImageRecompressionQuality	O
”	O
or	O
“	O
JpegRecompressionQuality	O
”	O
.	O
</s>
<s>
This	O
allows	O
a	O
decrease	O
in	O
payload	O
Recompress	O
PNGs	O
Losslessly	B-Algorithm
converts	O
png	O
images	O
into	O
images	O
with	O
higher	O
compression	O
Recompress	O
WEBPs	O
Replaces	O
WebP	O
images	O
with	O
smaller	O
re-compressed	O
versions	O
in	O
browsers	B-Application
which	O
support	O
webp	O
format	O
Strip	O
Image	O
Color	O
Profile	O
Removes	O
all	O
images’	O
color	O
profile	O
information	O
,	O
since	O
it	O
is	O
not	O
supported	O
by	O
most	O
of	O
the	O
browsers	B-Application
Strip	O
Image	O
Meta	O
Data	O
Removes	O
EXIF	O
meta	O
data	O
from	O
all	O
image	O
files	O
of	O
a	O
webpage	O
Reduce	O
JPEG	O
Subsampling	O
Reduces	O
color	O
sampling	O
rate	O
to	O
4:2:0	O
due	O
to	O
human	O
vision	O
sensitivity	O
to	O
changes	O
in	O
brightness	O
,	O
but	O
not	O
in	O
hue	O
or	O
saturation	O
.	O
</s>
<s>
This	O
group	O
of	O
filters	O
rewrites	O
the	O
contents	O
of	O
HTML	B-Language
files	I-Language
to	O
reduce	O
their	O
size	O
and	O
assure	O
latest	O
best	O
web	O
practices	O
compliance	O
.	O
</s>
<s>
Filter	O
Name	O
Description	O
Add	O
Head	O
Adds	O
a	O
<head> html tag if it is not found before <body> html tag, needed mainly for other filters to work properly, since a number of them add or modify data in the area marked with the <head> tag Collapse Whitespace  Deletes extra and unnecessary whitespaces between operators in html code Combine Heads  Groups the content of several <head>	O
tags	B-General_Concept
into	O
one	O
if	O
there	O
multiple	O
tags	B-General_Concept
,	O
preventing	O
incorrect	O
browser	B-Application
workflow	O
Convert	O
Meta	O
Tags	B-General_Concept
Adds	O
matching	O
present	O
meta	O
tags	B-General_Concept
response	O
header	O
,	O
avoiding	O
reparsing	O
delays	O
due	O
to	O
some	O
browsers	B-Application
“	O
http-equiv	O
”	O
attribute	O
requirements	O
Elide	O
Attributes	O
Removes	O
html	O
tags’	O
attributes	O
with	O
values	O
equal	O
to	O
default	O
values	O
,	O
which	O
reduces	O
the	O
total	O
amount	O
of	O
data	O
transferred	O
Local	O
Storage	O
Cache	O
Saves	O
inlined	B-Protocol
resources	I-Protocol
into	O
browser	B-Application
's	O
local	O
storage	O
on	O
the	O
first	O
view	O
of	O
a	O
page	O
,	O
and	O
loads	O
them	O
from	O
local	O
storage	O
on	O
subsequent	O
views	O
rather	O
than	O
inlining	O
them	O
again	O
.	O
</s>
<s>
The	O
PageSpeed	B-Application
Module	O
showed	O
the	O
most	O
significant	O
impact	O
on	O
decreasing	O
webpage	O
loading	O
times	O
,	O
payload	O
size	O
,	O
and	O
number	O
of	O
requests	O
when	O
compared	O
to	O
other	O
options	O
in	O
the	O
industry	O
.	O
</s>
<s>
Since	O
many	O
search	O
engines	O
,	O
including	O
Google	B-Application
,	O
employ	O
a	O
ranking	O
algorithm	O
which	O
is	O
affected	O
by	O
a	O
page	O
's	O
loading	O
speed	O
,	O
these	O
optimizations	O
can	O
impact	O
a	O
website	O
's	O
placement	O
in	O
search	O
results	O
.	O
</s>
<s>
As	O
of	O
February	O
2015	O
,	O
Google	B-Application
has	O
begun	O
testing	O
“	O
Slow	O
”	O
labels	O
on	O
mobile	O
devices	O
for	O
websites	O
that	O
exceed	O
a	O
certain	O
amount	O
of	O
loading	O
time	O
,	O
prompting	O
developers	O
to	O
examine	O
ways	O
to	O
increase	O
a	O
page	O
's	O
load	O
speed	O
.	O
</s>
<s>
PageSpeed	B-Application
Insights	O
is	O
an	O
online	O
synthetic	O
benchmark	O
tool.which	O
helps	O
in	O
identifying	O
performance	O
best	O
practices	O
on	O
any	O
single	O
URL	O
,	O
provides	O
suggestions	O
on	O
a	O
webpage	O
's	O
optimizations	O
,	O
and	O
suggests	O
overall	O
ideas	O
of	O
how	O
to	O
make	O
a	O
website	O
faster	O
.	O
</s>
<s>
This	O
tool	O
can	O
be	O
accessed	O
directly	O
in	O
any	O
browser	B-Application
.	O
</s>
<s>
Recent	O
versions	O
of	O
PageSpeed	B-Application
Insights	O
added	O
support	O
for	O
measuring	O
real-world	O
user	O
experience	O
using	O
the	O
Chrome	O
User	O
Experience	O
Report	O
.	O
</s>
<s>
Google	B-Application
Chrome	O
's	O
Elizabeth	O
Sweeny	O
and	O
Addy	O
Osmani	O
lead	O
PageSpeed	B-Application
Insights	O
and	O
announced	O
its	O
support	O
for	O
Core	O
Web	O
Vitals	O
in	O
2020	O
.	O
</s>
<s>
Pagespeed	B-Application
extension	O
is	O
an	O
extension	B-Protocol
of	I-Protocol
Chrome	I-Protocol
Browser	I-Protocol
and	O
is	O
a	O
part	O
of	O
Google	B-Application
Chrome	I-Application
Developer	I-Application
Tools	I-Application
.	O
</s>
<s>
Visitors	O
who	O
use	O
PageSpeed	B-Application
regularly	O
can	O
view	O
all	O
given	O
metrics	O
by	O
PageSpeed	B-Application
Insights	O
directly	O
in	O
a	O
browser	B-Application
and	O
download	O
webpage	O
resources	O
,	O
optimized	O
according	O
to	O
web	O
performance	O
best	O
practices	O
.	O
</s>
<s>
It	O
has	O
now	O
been	O
deprecated	O
and	O
Google	B-Application
recommends	O
the	O
online	O
version	O
be	O
used	O
instead	O
.	O
</s>
<s>
PageSpeed	B-Application
service	O
was	O
a	O
commercial	O
product	O
,	O
provided	O
by	O
Google	B-Application
Inc	I-Application
.	I-Application
</s>
<s>
Service	O
included	O
all	O
Pagespeed	B-Application
Module	O
optimizations	O
and	O
use	O
of	O
Google	B-Application
servers’	O
infrastructure	O
.	O
</s>
<s>
Google	B-Application
announced	O
the	O
deprecation	O
of	O
PageSpeed	B-Application
service	O
on	O
5	O
May	O
2015	O
and	O
turned	O
it	O
off	O
on	O
3	O
August	O
2015	O
.	O
</s>
