<s>
Bootstrap	B-Application
is	O
a	O
free	B-License
and	I-License
open-source	I-License
CSS	B-General_Concept
framework	I-General_Concept
directed	O
at	O
responsive	O
,	O
mobile-first	O
front-end	O
web	O
development	O
.	O
</s>
<s>
It	O
contains	O
HTML	B-Language
,	O
CSS	B-Language
and	O
(	O
optionally	O
)	O
JavaScript-based	O
design	O
templates	O
for	O
typography	O
,	O
forms	B-General_Concept
,	O
buttons	O
,	O
navigation	O
,	O
and	O
other	O
interface	O
components	O
.	O
</s>
<s>
,	O
Bootstrap	B-Application
is	O
the	O
14th	O
most	O
starred	O
project	O
(	O
4th	O
most	O
starred	O
library	O
)	O
on	O
GitHub	B-Application
,	O
with	O
over	O
161,000	O
stars	O
.	O
</s>
<s>
According	O
to	O
W3Techs	O
,	O
Bootstrap	B-Application
is	O
used	O
by	O
19.2	O
%	O
of	O
all	O
websites	O
.	O
</s>
<s>
Bootstrap	B-Application
is	O
an	O
HTML	B-Language
,	O
CSS	B-Language
and	O
JS	O
library	O
that	O
focuses	O
on	O
simplifying	O
the	O
development	O
of	O
informative	O
web	O
pages	O
(	O
as	O
opposed	O
to	O
web	B-Application
applications	I-Application
)	O
.	O
</s>
<s>
The	O
primary	O
purpose	O
of	O
adding	O
it	O
to	O
a	O
web	O
project	O
is	O
to	O
apply	O
Bootstrap	B-Application
's	O
choices	O
of	O
color	O
,	O
size	O
,	O
font	O
and	O
layout	O
to	O
that	O
project	O
.	O
</s>
<s>
Once	O
added	O
to	O
a	O
project	O
,	O
Bootstrap	B-Application
provides	O
basic	O
style	O
definitions	O
for	O
all	O
HTML	B-General_Concept
elements	I-General_Concept
.	O
</s>
<s>
The	O
result	O
is	O
a	O
uniform	O
appearance	O
for	O
prose	O
,	O
tables	O
and	O
form	O
elements	O
across	O
web	B-Application
browsers	I-Application
.	O
</s>
<s>
In	O
addition	O
,	O
developers	O
can	O
take	O
advantage	O
of	O
CSS	B-Language
classes	O
defined	O
in	O
Bootstrap	B-Application
to	O
further	O
customize	O
the	O
appearance	O
of	O
their	O
contents	O
.	O
</s>
<s>
For	O
example	O
,	O
Bootstrap	B-Application
has	O
provisioned	O
for	O
light	O
-	O
and	O
dark-colored	O
tables	O
,	O
page	O
headings	O
,	O
more	O
prominent	O
pull	O
quotes	O
,	O
and	O
text	O
with	O
a	O
highlight	O
.	O
</s>
<s>
Bootstrap	B-Application
also	O
comes	O
with	O
several	O
JavaScript	B-Language
components	O
which	O
do	O
not	O
require	O
other	O
libraries	O
like	O
jQuery	B-Language
.	O
</s>
<s>
Each	O
Bootstrap	B-Application
component	O
consists	O
of	O
an	O
HTML	B-Language
structure	O
,	O
CSS	B-Language
declarations	O
,	O
and	O
in	O
some	O
cases	O
accompanying	O
JavaScript	B-Language
code	O
.	O
</s>
<s>
The	O
most	O
prominent	O
components	O
of	O
Bootstrap	B-Application
are	O
its	O
layout	O
components	O
,	O
as	O
they	O
affect	O
an	O
entire	O
web	O
page	O
.	O
</s>
<s>
Once	O
a	O
container	O
is	O
in	O
place	O
,	O
other	O
Bootstrap	B-Application
layout	O
components	O
implement	O
a	O
CSS	B-Language
Flexbox	O
layout	O
through	O
defining	O
rows	O
and	O
columns	O
.	O
</s>
<s>
A	O
precompiled	O
version	O
of	O
Bootstrap	B-Application
is	O
available	O
in	O
the	O
form	O
of	O
one	O
CSS	B-Language
file	O
and	O
three	O
JavaScript	B-Language
files	O
that	O
can	O
be	O
readily	O
added	O
to	O
any	O
project	O
.	O
</s>
<s>
The	O
raw	O
form	O
of	O
Bootstrap	B-Application
,	O
however	O
,	O
enables	O
developers	O
to	O
implement	O
further	O
customization	O
and	O
size	O
optimizations	O
.	O
</s>
<s>
This	O
raw	O
form	O
is	O
modular	O
,	O
meaning	O
that	O
the	O
developer	O
can	O
remove	O
unneeded	O
components	O
,	O
apply	O
a	O
theme	O
and	O
modify	O
the	O
uncompiled	O
Sass	B-Language
files	O
.	O
</s>
<s>
Bootstrap	B-Application
,	O
originally	O
named	O
Twitter	B-Application
Blueprint	O
,	O
was	O
developed	O
by	O
Mark	B-Application
Otto	I-Application
and	O
Jacob	B-Application
Thornton	I-Application
at	O
Twitter	B-Application
as	O
a	O
framework	O
to	O
encourage	O
consistency	O
across	O
internal	O
tools	O
.	O
</s>
<s>
Before	O
Bootstrap	B-Application
,	O
various	O
libraries	O
were	O
used	O
for	O
interface	O
development	O
,	O
which	O
led	O
to	O
inconsistencies	O
and	O
a	O
high	O
maintenance	O
burden	O
.	O
</s>
<s>
After	O
a	O
few	O
months	O
of	O
development	O
by	O
a	O
small	O
group	O
,	O
many	O
developers	O
at	O
Twitter	B-Application
began	O
to	O
contribute	O
to	O
the	O
project	O
as	O
a	O
part	O
of	O
Hack	O
Week	O
,	O
a	O
hackathon-style	O
week	O
for	O
the	O
Twitter	B-Application
development	O
team	O
.	O
</s>
<s>
It	O
was	O
renamed	O
from	O
Twitter	B-Application
Blueprint	O
to	O
Bootstrap	B-Application
and	O
released	O
as	O
an	O
open-source	O
project	O
on	O
August	O
19	O
,	O
2011	O
.	O
</s>
<s>
On	O
January	O
31	O
,	O
2012	O
,	O
Bootstrap	B-Application
2	O
was	O
released	O
,	O
which	O
added	O
built-in	O
support	O
for	O
Glyphicons	O
,	O
several	O
new	O
components	O
,	O
as	O
well	O
as	O
changes	O
to	O
many	O
of	O
the	O
existing	O
components	O
.	O
</s>
<s>
This	O
version	O
supports	O
responsive	B-General_Concept
web	I-General_Concept
design	I-General_Concept
,	O
meaning	O
the	O
layout	O
of	O
web	O
pages	O
adjusts	O
dynamically	O
,	O
taking	O
into	O
account	O
the	O
characteristics	O
of	O
the	O
device	O
used	O
(	O
whether	O
desktop	O
,	O
tablet	O
,	O
mobile	O
phone	O
)	O
.	O
</s>
<s>
On	O
August	O
19	O
,	O
2013	O
,	O
Bootstrap	B-Application
3	O
,	O
was	O
released	O
.	O
</s>
<s>
It	O
redesigned	O
components	O
to	O
use	O
flat	B-Application
design	I-Application
and	O
a	O
mobile	O
first	O
approach	O
.	O
</s>
<s>
Bootstrap	B-Application
3	O
features	O
new	O
plugin	O
system	O
with	O
namespaced	O
events	O
.	O
</s>
<s>
Bootstrap	B-Application
3	O
dropped	O
Internet	B-Application
Explorer	I-Application
7	O
and	O
Firefox	B-Application
3.6	O
support	O
,	O
but	O
there	O
is	O
an	O
optional	O
polyfill	B-Protocol
for	O
these	O
browsers	B-Application
.	O
</s>
<s>
Otto	O
announced	O
Bootstrap	B-Application
4	O
on	O
October	O
29	O
,	O
2014	O
.	O
</s>
<s>
The	O
first	O
alpha	O
version	O
of	O
Bootstrap	B-Application
4	O
was	O
released	O
on	O
August	O
19	O
,	O
2015	O
.	O
</s>
<s>
Otto	O
suspended	O
work	O
on	O
Bootstrap	B-Application
3	O
on	O
September	O
6	O
,	O
2016	O
,	O
to	O
free	O
up	O
time	O
to	O
work	O
on	O
Bootstrap	B-Application
4	O
.	O
</s>
<s>
Bootstrap	B-Application
4	O
was	O
finalized	O
on	O
January	O
18	O
,	O
2018	O
.	O
</s>
<s>
Bootstrap	B-Application
4	O
supports	O
the	O
latest	O
versions	O
of	O
Google	B-Application
Chrome	I-Application
,	O
Firefox	B-Application
,	O
Internet	B-Application
Explorer	I-Application
,	O
Opera	B-Application
,	O
and	O
Safari	B-Application
(	O
except	O
on	O
Windows	O
)	O
.	O
</s>
<s>
It	O
additionally	O
supports	O
back	O
to	O
IE10	B-Application
and	O
the	O
latest	O
Firefox	B-Application
Extended	O
Support	O
Release	O
(	O
ESR	O
)	O
.	O
</s>
<s>
Bootstrap	B-Application
5	O
was	O
officially	O
released	O
on	O
May	O
5	O
,	O
2021	O
.	O
</s>
