<s>
Zstandard	B-Language
,	O
commonly	O
known	O
by	O
the	O
name	O
of	O
its	O
reference	O
implementation	O
zstd	B-Language
,	O
is	O
a	O
lossless	B-Algorithm
data	I-Algorithm
compression	I-Algorithm
algorithm	O
developed	O
by	O
Yann	O
Collet	O
at	O
Facebook	B-Application
.	I-Application
</s>
<s>
Zstd	B-Language
is	O
the	O
reference	O
implementation	O
in	O
C	B-Language
.	O
Version	O
1	O
of	O
this	O
implementation	O
was	O
released	O
as	O
open-source	B-Application
software	I-Application
on	O
31	O
August	O
2016	O
.	O
</s>
<s>
Zstandard	B-Language
was	O
designed	O
to	O
give	O
a	O
compression	B-General_Concept
ratio	I-General_Concept
comparable	O
to	O
that	O
of	O
the	O
DEFLATE	B-Algorithm
algorithm	O
(	O
developed	O
in	O
1991	O
and	O
used	O
in	O
the	O
original	O
ZIP	B-General_Concept
and	O
gzip	B-Application
programs	O
)	O
,	O
but	O
faster	O
,	O
especially	O
for	O
decompression	O
.	O
</s>
<s>
It	O
is	O
tunable	O
with	O
compression	O
levels	O
ranging	O
from	O
negative	O
7	O
(	O
fastest	O
)	O
to	O
22	O
(	O
slowest	O
in	O
compression	O
speed	O
,	O
but	O
best	O
compression	B-General_Concept
ratio	I-General_Concept
)	O
.	O
</s>
<s>
Starting	O
from	O
version	O
1.3.2	O
(	O
October	O
2017	O
)	O
,	O
zstd	B-Language
optionally	O
implements	O
very	O
long	O
range	O
search	O
and	O
deduplication	O
(	O
,	O
128MiB	O
window	O
)	O
similar	O
to	O
rzip	B-Application
or	O
lrzip	O
.	O
</s>
<s>
Zstandard	B-Language
command-line	O
has	O
an	O
"	O
adaptive	O
"	O
(	O
)	O
mode	O
that	O
varies	O
compression	O
level	O
depending	O
on	O
I/O	O
conditions	O
,	O
mainly	O
how	O
fast	O
it	O
can	O
write	O
the	O
output	O
.	O
</s>
<s>
Zstd	B-Language
at	O
its	O
maximum	O
compression	O
level	O
gives	O
a	O
compression	B-General_Concept
ratio	I-General_Concept
close	O
to	O
lzma	B-General_Concept
,	O
</s>
<s>
lzham	O
,	O
and	O
ppmx	O
,	O
and	O
Zstandard	B-Language
reaches	O
the	O
current	O
Pareto	O
frontier	O
,	O
as	O
it	O
decompresses	O
faster	O
than	O
any	O
other	O
currently	O
available	O
algorithm	O
with	O
similar	O
or	O
better	O
compression	B-General_Concept
ratio	I-General_Concept
.	O
</s>
<s>
Dictionaries	O
can	O
have	O
a	O
large	O
impact	O
on	O
the	O
compression	B-General_Concept
ratio	I-General_Concept
of	O
small	O
files	O
,	O
so	O
Zstandard	B-Language
can	O
use	O
a	O
user-provided	O
compression	O
dictionary	O
.	O
</s>
<s>
In	O
particular	O
,	O
one	O
dictionary	O
can	O
be	O
loaded	O
to	O
process	O
large	O
sets	O
of	O
files	O
with	O
redundancy	O
between	O
files	O
,	O
but	O
not	O
necessarily	O
within	O
each	O
file	O
,	O
e.g.	O
,	O
log	B-Application
files	I-Application
.	O
</s>
<s>
Zstandard	B-Language
combines	O
a	O
dictionary-matching	O
stage	O
(	O
LZ77	O
)	O
with	O
a	O
large	O
search	O
window	O
and	O
a	O
fast	O
entropy-coding	B-Algorithm
stage	O
.	O
</s>
<s>
It	O
uses	O
both	O
Huffman	B-General_Concept
coding	I-General_Concept
(	O
used	O
for	O
entries	O
in	O
the	O
Literals	O
section	O
)	O
and	O
finite-state	O
entropy	O
(	O
FSE	O
)	O
-	O
a	O
fast	O
tabled	O
version	O
of	O
ANS	O
,	O
tANS	O
,	O
used	O
for	O
entries	O
in	O
the	O
Sequences	O
section	O
.	O
</s>
<s>
The	O
Linux	B-Operating_System
kernel	I-Operating_System
has	O
included	O
Zstandard	B-Language
since	O
November	O
2017	O
(	O
version	O
4.14	O
)	O
as	O
a	O
compression	O
method	O
for	O
the	O
btrfs	B-Operating_System
and	O
squashfs	B-Application
filesystems	O
.	O
</s>
<s>
In	O
2017	O
,	O
Allan	O
Jude	O
integrated	O
Zstandard	B-Language
into	O
the	O
FreeBSD	B-Operating_System
kernel	B-Operating_System
,	O
and	O
it	O
was	O
subsequently	O
integrated	O
as	O
a	O
compressor	O
option	O
for	O
core	O
dumps	O
(	O
both	O
user	O
programs	O
and	O
kernel	B-Operating_System
panics	O
)	O
.	O
</s>
<s>
It	O
was	O
also	O
used	O
to	O
create	O
a	O
proof-of-concept	O
OpenZFS	B-Operating_System
compression	O
method	O
which	O
was	O
integrated	O
in	O
2020	O
.	O
</s>
<s>
The	O
AWS	O
Redshift	O
and	O
RocksDB	B-Language
databases	O
include	O
support	O
for	O
field	O
compression	O
using	O
Zstandard	B-Language
.	O
</s>
<s>
In	O
March	O
2018	O
,	O
Canonical	O
tested	O
the	O
use	O
of	O
zstd	B-Language
as	O
a	O
deb	O
package	O
compression	O
method	O
by	O
default	O
for	O
the	O
Ubuntu	B-Operating_System
Linux	I-Operating_System
distribution	I-Operating_System
.	O
</s>
<s>
Compared	O
with	O
xz	B-Language
compression	O
of	O
deb	O
packages	O
,	O
zstd	B-Language
at	O
level	O
19	O
decompresses	O
significantly	O
faster	O
,	O
but	O
at	O
the	O
cost	O
of	O
6%	O
larger	O
package	O
files	O
.	O
</s>
<s>
Support	O
was	O
added	O
to	O
Debian	O
(	O
and	O
subsequently	O
,	O
Ubuntu	B-Operating_System
)	O
in	O
April	O
2018	O
(	O
in	O
version	O
1.6	O
~	O
rc1	O
)	O
.	O
</s>
<s>
In	O
2018	O
the	O
algorithm	O
was	O
published	O
as	O
,	O
which	O
also	O
defines	O
an	O
associated	O
media	B-Application
type	I-Application
"	O
application/zstd	O
"	O
,	O
filename	O
extension	O
"	O
zst	O
"	O
,	O
and	O
HTTP	B-Protocol
content	I-Protocol
encoding	I-Protocol
"	O
zstd	B-Language
"	O
.	O
</s>
<s>
Arch	O
Linux	B-Operating_System
added	O
support	O
for	O
zstd	B-Language
as	O
a	O
package	O
compression	O
method	O
in	O
October	O
2019	O
with	O
the	O
release	O
of	O
the	O
pacman5.2	O
package	O
manager	O
and	O
in	O
January	O
2020	O
switched	O
from	O
xz	B-Language
to	O
zstd	B-Language
for	O
the	O
packages	O
in	O
the	O
official	O
repository	O
.	O
</s>
<s>
Arch	O
uses	O
zstd	B-Language
-c	O
-T0	O
--ultra	O
-20	O
-	O
,	O
the	O
size	O
of	O
all	O
compressed	O
packages	O
combined	O
increased	O
by	O
0.8	O
%	O
(	O
compared	O
to	O
xz	B-Language
)	O
,	O
the	O
decompression	O
speed	O
is	O
14	O
times	O
faster	O
,	O
decompression	O
memory	O
increased	O
by	O
50MiB	O
when	O
using	O
multiple	O
threads	O
,	O
compression	O
memory	O
increases	O
but	O
scales	O
with	O
the	O
number	O
of	O
threads	O
used	O
.	O
</s>
<s>
Arch	O
Linux	B-Operating_System
later	O
also	O
switched	O
to	O
zstd	B-Language
as	O
default	O
compression	B-General_Concept
algorithm	I-General_Concept
for	O
mkinitcpio	O
initial	B-Application
ramdisk	I-Application
generator	O
.	O
</s>
<s>
Fedora	O
added	O
ZStandard	B-Language
support	O
to	O
RPM	B-Application
in	O
May	O
2018	O
(	O
Fedora	O
release	O
28	O
)	O
and	O
used	O
it	O
for	O
packaging	O
the	O
release	O
in	O
October	O
2019	O
(	O
Fedora31	O
)	O
.	O
</s>
<s>
In	O
Fedora33	O
,	O
the	O
filesystem	O
is	O
compressed	O
by	O
default	O
with	O
zstd	B-Language
.	O
</s>
<s>
Full	O
implementation	O
of	O
the	O
algorithm	O
with	O
an	O
option	O
to	O
choose	O
the	O
compression	O
level	O
is	O
used	O
in	O
the	O
.NSZ/.XCZ	O
file	O
formats	O
developed	O
by	O
the	O
homebrew	B-Application
community	O
for	O
the	O
Nintendo	B-Application
Switch	I-Application
hybrid	O
game	O
console	O
.	O
</s>
<s>
Similarly	O
,	O
it	O
is	O
also	O
one	O
of	O
many	O
supported	O
compression	B-General_Concept
algorithms	I-General_Concept
in	O
the	O
.RVZ	O
Nintendo	B-Operating_System
Wii	I-Operating_System
and	O
Nintendo	B-Application
GameCube	I-Application
disc	O
image	O
file	O
format	O
.	O
</s>
<s>
In	O
2020	O
,	O
Zstandard	B-Language
was	O
implemented	O
in	O
version	O
6.3.8	O
of	O
the	O
zip	B-General_Concept
file	I-General_Concept
format	I-General_Concept
with	O
codec	O
number93	O
.	O
</s>
<s>
Previous	O
number20	O
of	O
version	O
6.3.7	O
was	O
deprecated	O
,	O
so	O
a	O
second	O
file	O
format	O
with	O
zip	B-General_Concept
is	O
available	O
for	O
Zstandard	B-Language
files	O
.	O
</s>
<s>
New	O
versions	O
of	O
zip	B-General_Concept
programs	O
often	O
support	O
this	O
new	O
feature	O
.	O
</s>
<s>
7-Zip	B-Language
ZS	O
,	O
a	O
fork	O
of	O
7-Zip	B-Language
FM	I-Language
with	O
Zstandard	B-Language
(	O
and	O
other	O
formats	O
)	O
support	O
,	O
is	O
developed	O
by	O
Tino	O
Reichardt	O
.	O
</s>
<s>
Actual	O
Zstandard	B-Language
1.5.0	O
support	O
is	O
here	O
.	O
</s>
<s>
Modern7z	O
,	O
a	O
Zstandard	B-Language
(	O
and	O
other	O
formats	O
)	O
plugin	O
for	O
7-Zip	B-Language
FM	I-Language
is	O
developed	O
by	O
Denis	O
Anisimov	O
(	O
TC4shell	O
)	O
.	O
</s>
<s>
p7zip	B-Language
also	O
supports	O
in	O
a	O
new	O
version	O
Zstandard1.4.9	O
.	O
</s>
<s>
The	O
reference	O
implementation	O
is	O
licensed	O
under	O
the	O
BSD	B-Operating_System
license	I-Operating_System
,	O
published	O
at	O
GitHub	B-Application
.	O
</s>
