<s>
Zulip	B-Protocol
is	O
an	O
open	B-License
source	I-License
chat	B-Protocol
and	O
collaborative	B-Application
software	I-Application
created	O
by	O
Jeff	O
Arnold	O
,	O
Waseem	O
Daher	O
,	O
Jessica	O
McKellar	O
,	O
and	O
Tim	O
Abbott	O
in	O
2012	O
.	O
</s>
<s>
Today	O
,	O
it	O
is	O
one	O
of	O
the	O
free	O
and	O
open	B-License
source	I-License
alternatives	O
to	O
Slack	B-Protocol
,	O
with	O
over	O
40,000	O
commits	O
contributed	O
by	O
660	O
people	O
.	O
</s>
<s>
In	O
Zulip	B-Protocol
,	O
communication	O
occurs	O
in	O
streams	O
(	O
which	O
are	O
like	O
channels	O
in	O
IRC	B-Protocol
)	O
.	O
</s>
<s>
Each	O
stream	O
can	O
have	O
several	O
topics	O
–	O
Zulip	B-Protocol
features	O
a	O
unique	O
threading	O
model	O
,	O
in	O
which	O
each	O
message	O
also	O
has	O
a	O
topic	O
,	O
along	O
with	O
the	O
content	O
.	O
</s>
<s>
Zulip	B-Protocol
claims	O
that	O
this	O
improves	O
productivity	O
by	O
"	O
making	O
it	O
easy	O
to	O
catch	O
up	O
after	O
a	O
day	O
of	O
meetings	O
"	O
.	O
</s>
<s>
Apart	O
from	O
this	O
,	O
Zulip	B-Protocol
offers	O
standard	O
features	O
found	O
in	O
collaboration	O
apps	O
like	O
message	O
reactions	O
,	O
message	O
search	O
history	O
,	O
polls	O
,	O
private	O
messaging	O
,	O
group	O
messaging	O
etc	O
.	O
</s>
<s>
Zulip	B-Protocol
streams	O
can	O
be	O
private	O
or	O
public	O
–	O
only	O
people	O
invited	O
to	O
a	O
private	O
stream	O
can	O
view	O
messages	O
in	O
it	O
,	O
while	O
anyone	O
within	O
an	O
organization	O
can	O
join	O
a	O
public	O
stream	O
.	O
</s>
<s>
Messages	O
in	O
Zulip	B-Protocol
can	O
be	O
sent	O
in	O
plain-text	O
or	O
formatted	O
using	O
markdown	O
,	O
along	O
with	O
images	O
,	O
links	O
,	O
and	O
file	O
attachments	O
.	O
</s>
<s>
Zulip	B-Protocol
also	O
offers	O
support	O
for	O
native	O
integrations	O
with	O
hundreds	O
of	O
services	O
,	O
which	O
can	O
extend	O
its	O
functionality	O
.	O
</s>
<s>
Apart	O
from	O
the	O
web	O
interface	O
,	O
Zulip	B-Protocol
officially	O
supports	O
other	O
clients	O
,	O
all	O
of	O
which	O
are	O
open	O
sourced	O
:	O
</s>
<s>
for	O
iOS	B-Application
and	O
Android	B-Application
.	O
</s>
<s>
for	O
Windows	O
,	O
OSX	B-Operating_System
and	O
Linux	B-Application
.	O
</s>
<s>
of	O
Linux	B-Application
,	O
OSX	B-Operating_System
and	O
Windows	O
(	O
WSL	O
)	O
.	O
</s>
