<s>
Superfeedr	B-Application
is	O
a	O
feed	O
API	B-General_Concept
built	O
on	O
WebSub	B-Application
,	O
that	O
is	O
sometimes	O
referred	O
to	O
as	O
PuSH	B-Application
.	O
</s>
<s>
It	O
transforms	O
a	O
variety	O
of	O
feeds	O
into	O
a	O
standardized	O
RSS	O
,	O
Atom	B-Application
,	O
or	O
JSON	B-General_Concept
format	O
and	O
distributes	O
(	O
or	O
"	O
pushes	O
"	O
)	O
them	O
via	O
WebSub	B-Application
or	O
XMPP	B-Protocol
.	O
</s>
<s>
Superfeedr	B-Application
was	O
launched	O
by	O
in	O
2009	O
by	O
parent	O
company	O
Notifixious	O
.	O
</s>
<s>
While	O
Notifixious	O
 '	O
website	O
went	O
offline	O
sometime	O
between	O
September	O
23	O
,	O
2009	O
,	O
and	O
January	O
5	O
,	O
2010	O
,	O
Superfeedr	B-Application
has	O
remained	O
online	O
and	O
available	O
.	O
</s>
<s>
While	O
the	O
website	O
of	O
Notifixious	O
,	O
the	O
parent	O
company	O
of	O
Superfeedr	B-Application
,	O
is	O
no	O
longer	O
available	O
,	O
Superfeedr	B-Application
continues	O
to	O
refer	O
to	O
it	O
in	O
the	O
terms	O
of	O
service	O
for	O
the	O
site	O
.	O
</s>
<s>
Superfeedr	B-Application
was	O
bought	O
by	O
Medium	B-Protocol
in	O
2016	O
.	O
</s>
<s>
PuSH	B-Application
is	O
a	O
protocol	O
that	O
relies	O
on	O
webhooks	B-Protocol
to	O
push	B-Application
feed	O
updates	O
in	O
real-time	O
from	O
publishers	O
to	O
subscribers	O
in	O
a	O
decentralized	O
manner	O
.	O
</s>
<s>
PuSH	B-Application
builds	O
on	O
existing	O
protocols	O
,	O
ensuring	O
that	O
polling	O
infrastructures	O
currently	O
in	O
use	O
are	O
not	O
changed	O
or	O
broken	O
on	O
implementation	O
,	O
and	O
that	O
polling	O
is	O
still	O
available	O
as	O
a	O
back-up	O
.	O
</s>
<s>
Superfeedr	B-Application
acts	O
as	O
a	O
“	O
default	O
”	O
hub	O
:	O
a	O
hub	O
that	O
works	O
for	O
an	O
RSS	O
or	O
Atom	B-Application
feed	I-Application
,	O
whether	O
their	O
publisher	O
supports	O
the	O
protocol	O
or	O
not	O
.	O
</s>
<s>
Superfeedr	B-Application
also	O
built	O
a	O
feed	O
graph	O
to	O
identify	O
updates	O
in	O
related	O
feeds	O
to	O
avoid	O
polling	O
feeds	O
too	O
aggressively	O
.	O
</s>
<s>
Publishers	O
are	O
web	B-Application
applications	I-Application
that	O
host	O
their	O
WebSub	B-Application
hub	O
with	O
Superfeedr	B-Application
,	O
while	O
subscribers	O
are	O
applications	O
that	O
consume	O
the	O
feed	O
API	B-General_Concept
to	O
aggregate	O
feeds	O
from	O
across	O
the	O
web	O
.	O
</s>
<s>
Trackers	O
,	O
a	O
new	O
type	O
of	O
user	O
,	O
was	O
added	O
to	O
Superfeedr	B-Application
in	O
April	O
2015	O
.	O
</s>
<s>
The	O
tracking	O
feature	O
(	O
a	O
prospective	B-General_Concept
search	I-General_Concept
engine	I-General_Concept
)	O
is	O
scaled	O
to	O
parse	O
millions	O
of	O
feeds	O
and	O
their	O
metadata	O
to	O
add	O
extra	O
filtering	O
options	O
.	O
</s>
<s>
In	O
late	O
2009	O
,	O
Mark	O
Cuban	O
and	O
Betaworks	O
invested	O
in	O
Superfeedr	B-Application
during	O
a	O
round	O
of	O
seed	O
funding	O
.	O
</s>
