<s>
Clean	B-Protocol
URLs	I-Protocol
(	O
also	O
known	O
as	O
user-friendly	B-Protocol
URLs	I-Protocol
,	O
pretty	B-Protocol
URLs	I-Protocol
,	O
search	O
engine-friendly	O
URLs	O
or	O
RESTful	B-Protocol
URLs	I-Protocol
)	O
are	O
web	O
addresses	O
or	O
Uniform	O
Resource	O
Locator	O
(	O
URLs	O
)	O
intended	O
to	O
improve	O
the	O
usability	B-General_Concept
and	O
accessibility	O
of	O
a	O
website	O
,	O
web	B-Application
application	I-Application
,	O
or	O
web	O
service	O
by	O
being	O
immediately	O
and	O
intuitively	O
meaningful	O
to	O
non-expert	O
users	O
.	O
</s>
<s>
Such	O
URL	O
schemes	O
tend	O
to	O
reflect	O
the	O
conceptual	O
structure	O
of	O
a	O
collection	O
of	O
information	O
and	O
decouple	B-Application
the	O
user	B-Application
interface	I-Application
from	O
a	O
server	O
's	O
internal	O
representation	O
of	O
information	O
.	O
</s>
<s>
Other	O
reasons	O
for	O
using	O
clean	B-Protocol
URLs	I-Protocol
include	O
search	B-Application
engine	I-Application
optimization	O
(	O
SEO	O
)	O
,	O
conforming	O
to	O
the	O
representational	B-Protocol
state	I-Protocol
transfer	I-Protocol
(	O
REST	O
)	O
style	O
of	O
software	O
architecture	O
,	O
and	O
ensuring	O
that	O
individual	O
web	O
resources	O
remain	O
consistently	O
at	O
the	O
same	O
URL	O
.	O
</s>
<s>
Clean	B-Protocol
URLs	I-Protocol
also	O
do	O
not	O
contain	O
implementation	O
details	O
of	O
the	O
underlying	O
web	B-Application
application	I-Application
.	O
</s>
<s>
For	O
example	O
,	O
many	O
URLs	O
include	O
the	O
filename	B-Device
of	O
a	O
server-side	B-Language
script	I-Language
,	O
such	O
as	O
,	O
or	O
.	O
</s>
<s>
Likewise	O
,	O
when	O
URLs	O
are	O
not	O
"	O
clean	O
"	O
,	O
if	O
the	O
site	O
database	O
is	O
moved	O
or	O
restructured	O
it	O
has	O
the	O
potential	O
to	O
cause	O
broken	O
links	O
,	O
both	O
internally	O
and	O
from	O
external	O
sites	O
,	O
the	O
latter	O
of	O
which	O
can	O
lead	O
to	O
removal	O
from	O
search	B-Application
engine	I-Application
listings	O
.	O
</s>
<s>
The	O
use	O
of	O
clean	B-Protocol
URLs	I-Protocol
presents	O
a	O
consistent	O
location	O
for	O
resources	O
to	O
user-agents	B-Protocol
regardless	O
of	O
internal	O
structure	O
.	O
</s>
<s>
A	O
further	O
potential	O
benefit	O
to	O
the	O
use	O
of	O
clean	B-Protocol
URLs	I-Protocol
is	O
that	O
the	O
concealment	O
of	O
internal	O
server	O
or	O
application	O
information	O
can	O
improve	O
the	O
security	O
of	O
a	O
system	O
.	O
</s>
<s>
A	O
URL	O
will	O
often	O
comprise	O
a	O
path	O
,	O
script	O
name	O
,	O
and	O
query	B-Protocol
string	I-Protocol
.	O
</s>
<s>
The	O
query	B-Protocol
string	I-Protocol
parameters	O
dictate	O
the	O
content	O
to	O
show	O
on	O
the	O
page	O
,	O
and	O
frequently	O
include	O
information	O
opaque	O
or	O
irrelevant	O
to	O
users	O
—	O
such	O
as	O
internal	O
numeric	O
identifiers	O
for	O
values	O
in	O
a	O
database	O
,	O
illegibly	O
encoded	O
data	O
,	O
session	B-Protocol
IDs	I-Protocol
,	O
implementation	O
details	O
,	O
and	O
so	O
on	O
.	O
</s>
<s>
Clean	B-Protocol
URLs	I-Protocol
,	O
by	O
contrast	O
,	O
contain	O
only	O
the	O
path	O
of	O
a	O
resource	O
,	O
in	O
a	O
hierarchy	O
that	O
reflects	O
some	O
logical	O
structure	O
that	O
users	O
can	O
easily	O
interpret	O
and	O
manipulate	O
.	O
</s>
<s>
Original	O
URL	O
Clean	B-Protocol
URL	I-Protocol
http:/index.php	O
?	O
title	O
=	O
Clean_URL	O
http	O
:	O
</s>
<s>
The	O
implementation	O
of	O
clean	B-Protocol
URLs	I-Protocol
involves	O
URL	O
mapping	O
via	O
pattern	O
matching	O
or	O
transparent	O
rewriting	B-Protocol
techniques	O
.	O
</s>
<s>
As	O
this	O
usually	O
takes	O
place	O
on	O
the	O
server	O
side	O
,	O
the	O
clean	B-Protocol
URL	I-Protocol
is	O
often	O
the	O
only	O
form	O
seen	O
by	O
the	O
user	O
.	O
</s>
<s>
For	O
search	B-Application
engine	I-Application
optimization	O
purposes	O
,	O
web	O
developers	O
often	O
take	O
this	O
opportunity	O
to	O
include	O
relevant	O
keywords	O
in	O
the	O
URL	O
and	O
remove	O
irrelevant	O
words	O
.	O
</s>
<s>
Common	O
words	O
that	O
are	O
removed	O
include	O
articles	O
and	O
conjunctions	O
,	O
while	O
descriptive	O
keywords	O
are	O
added	O
to	O
increase	O
user-friendliness	B-General_Concept
and	O
improve	O
search	B-Application
engine	I-Application
rankings	O
.	O
</s>
<s>
A	O
fragment	O
identifier	O
can	O
be	O
included	O
at	O
the	O
end	O
of	O
a	O
clean	B-Protocol
URL	I-Protocol
for	O
references	O
within	O
a	O
page	O
,	O
and	O
need	O
not	O
be	O
user-readable	O
.	O
</s>
<s>
Some	O
systems	O
define	O
a	O
slug	O
as	O
the	O
part	O
of	O
a	O
URL	O
that	O
identifies	O
a	O
page	O
in	O
human-readable	B-General_Concept
keywords	O
.	O
</s>
<s>
It	O
is	O
usually	O
the	O
end	O
part	O
of	O
the	O
URL	O
(	O
specifically	O
of	O
the	O
path	O
/	O
pathinfo	O
part	O
)	O
,	O
which	O
can	O
be	O
interpreted	O
as	O
the	O
name	O
of	O
the	O
resource	O
,	O
similar	O
to	O
the	O
basename	B-Application
in	O
a	O
filename	B-Device
or	O
the	O
title	O
of	O
a	O
page	O
.	O
</s>
<s>
Slugs	O
are	O
typically	O
generated	O
automatically	O
from	O
a	O
page	O
title	O
but	O
can	O
also	O
be	O
entered	O
or	O
altered	O
manually	O
,	O
so	O
that	O
while	O
the	O
page	O
title	O
remains	O
designed	O
for	O
display	O
and	O
human	O
readability	O
,	O
its	O
slug	O
may	O
be	O
optimized	O
for	O
brevity	O
or	O
for	O
consumption	O
by	O
search	B-Application
engines	I-Application
,	O
as	O
well	O
as	O
providing	O
recipients	O
of	O
a	O
shared	O
bare	O
URL	O
with	O
the	O
rough	O
idea	O
of	O
the	O
page	O
's	O
topic	O
.	O
</s>
<s>
Another	O
benefit	O
of	O
URL	O
slugs	O
is	O
the	O
facilitated	O
ability	O
to	O
find	O
a	O
desired	O
page	O
out	O
of	O
a	O
long	O
list	O
of	O
URLs	O
without	O
page	O
titles	O
,	O
such	O
as	O
a	O
minimal	O
list	O
of	O
opened	O
tabs	O
exported	O
using	O
a	O
browser	B-Protocol
extension	I-Protocol
,	O
and	O
the	O
ability	O
to	O
preview	O
the	O
approximate	O
title	O
of	O
a	O
target	O
page	O
in	O
the	O
browser	O
if	O
hyperlinked	O
to	O
without	O
title	O
.	O
</s>
<s>
Should	O
a	O
tool	O
to	O
save	O
web	O
pages	O
locally	O
using	O
the	O
string	O
after	O
the	O
last	O
slash	O
as	O
the	O
default	O
file	O
name	O
,	O
like	O
wget	B-Protocol
does	O
,	O
a	O
slug	O
makes	O
the	O
file	O
name	O
more	O
descriptive	O
.	O
</s>
<s>
Websites	O
that	O
make	O
use	O
of	O
slugs	O
include	O
Stack	O
Exchange	O
Network	O
with	O
question	O
title	O
after	O
slash	O
,	O
and	O
Instagram	B-Application
with	O
?	O
taken-by	O
=	O
username	O
URL	B-Protocol
parameter	I-Protocol
.	O
</s>
