<s>
MHTML	B-Application
,	O
an	O
initialism	O
of	O
"	O
MIME	B-Protocol
encapsulation	O
of	O
aggregate	O
HTML	B-Language
documents	O
"	O
,	O
is	O
a	O
Web	B-General_Concept
archive	I-General_Concept
file	I-General_Concept
format	O
used	O
to	O
combine	O
,	O
in	O
a	O
single	O
computer	B-Operating_System
file	I-Operating_System
,	O
the	O
HTML	B-Language
code	I-Language
and	O
its	O
companion	O
resources	O
(	O
such	O
as	O
images	O
)	O
that	O
are	O
represented	O
by	O
external	O
hyperlinks	O
in	O
the	O
web	O
page	O
's	O
HTML	B-Language
code	I-Language
.	O
</s>
<s>
The	O
content	O
of	O
an	O
MHTML	B-Application
file	O
is	O
encoded	O
using	O
the	O
same	O
techniques	O
that	O
were	O
first	O
developed	O
for	O
HTML	B-Language
email	O
messages	O
,	O
using	O
the	O
MIME	B-Protocol
content	B-Application
type	I-Application
multipart/related	O
.	O
</s>
<s>
MHTML	B-Application
files	O
use	O
an	O
.mhtml	O
or	O
.mht	B-Application
filename	O
extension	O
.	O
</s>
<s>
The	O
second	O
part	O
is	O
normally	O
HTML	B-Language
code	I-Language
.	O
</s>
<s>
Subsequent	O
parts	O
are	O
additional	O
resources	O
identified	O
by	O
their	O
original	O
uniform	O
resource	O
locators	O
(	O
URLs	O
)	O
and	O
encoded	O
in	O
base64	B-Protocol
binary-to-text	O
encoding	O
.	O
</s>
<s>
MHTML	B-Application
was	O
proposed	O
as	O
an	O
open	O
standard	O
,	O
then	O
circulated	O
in	O
a	O
revised	O
edition	O
in	O
1999	O
as	O
RFC	O
2557	O
.	O
</s>
<s>
The	O
.mhtml	O
(	O
Web	B-General_Concept
archive	I-General_Concept
)	O
and	O
.eml	O
(	O
email	O
)	O
filename	O
extensions	O
are	O
interchangeable	O
:	O
either	O
filename	O
extension	O
can	O
be	O
changed	O
from	O
one	O
to	O
the	O
other	O
.	O
</s>
<s>
An	O
.eml	O
message	O
can	O
be	O
sent	O
by	O
e-mail	O
,	O
and	O
it	O
can	O
be	O
displayed	O
by	O
an	O
email	B-Protocol
client	I-Protocol
.	O
</s>
<s>
An	O
email	O
message	O
can	O
be	O
saved	O
using	O
a	O
.mhtml	O
or	O
.mht	B-Application
filename	O
extension	O
and	O
then	O
opened	O
for	O
display	O
in	O
a	O
web	B-Application
browser	I-Application
or	O
for	O
editing	O
other	O
programs	O
,	O
including	O
word	B-General_Concept
processors	I-General_Concept
and	O
text	B-Application
editors	I-Application
.	O
</s>
<s>
The	O
header	O
of	O
an	O
MHTML	B-Application
file	O
contains	O
metadata	O
such	O
as	O
a	O
date	O
and	O
time	O
stamp	O
,	O
page	O
title	O
,	O
the	O
source	O
URL	O
,	O
and	O
a	O
unique	O
randomized	O
boundary	O
string	O
for	O
separating	O
resources	O
contained	O
within	O
the	O
file	O
.	O
</s>
<s>
Then	O
,	O
the	O
page	O
resources	O
are	O
contained	O
sequentially	O
,	O
starting	O
with	O
the	O
page	O
's	O
rendered	O
HTML	B-Language
source	O
code	O
.	O
</s>
<s>
Each	O
resource	O
has	O
its	O
own	O
metadata	O
header	O
which	O
specifies	O
its	O
MIME	B-Application
type	I-Application
and	O
the	O
original	O
location	O
.	O
</s>
<s>
The	O
MHTML	B-Application
file	O
ends	O
with	O
a	O
boundary	O
string	O
that	O
is	O
not	O
followed	O
by	O
any	O
data	O
.	O
</s>
<s>
Some	O
browsers	B-Application
support	O
the	O
MHTML	B-Application
format	O
,	O
either	O
directly	O
or	O
through	O
third-party	O
extensions	O
,	O
but	O
the	O
process	O
for	O
saving	O
a	O
web	O
page	O
along	O
with	O
its	O
resources	O
as	O
an	O
MHTML	B-Application
file	O
is	O
not	O
standardized	O
.	O
</s>
<s>
Due	O
to	O
this	O
,	O
a	O
web	O
page	O
saved	O
as	O
an	O
MHTML	B-Application
file	O
using	O
one	O
browser	B-Application
may	O
render	O
differently	O
on	O
another	O
.	O
</s>
<s>
As	O
of	O
version	O
5.0	O
,	O
IE	B-Application
was	O
the	O
first	O
browser	B-Application
to	O
support	O
reading	O
and	O
saving	O
web	O
pages	O
and	O
external	O
resources	O
to	O
a	O
single	O
MHTML	B-Application
file	O
.	O
</s>
<s>
As	O
of	O
switching	O
to	O
the	O
Chromium	B-Language
source	O
code	O
,	O
Edge	O
supports	O
saving	O
as	O
MHTML	B-Application
.	O
</s>
<s>
Support	O
for	O
saving	O
web	O
pages	O
as	O
MHTML	B-Application
files	O
was	O
made	O
available	O
in	O
the	O
Opera	B-Application
9.0	O
web	B-Application
browser	I-Application
.	O
</s>
<s>
From	O
Opera	B-Application
9.50	O
through	O
the	O
rest	O
of	O
the	O
Presto-based	O
Opera	B-Application
product	O
line	O
(	O
currently	O
at	O
Opera	B-Application
12.16	O
as	O
of	O
19	O
July	O
2013	O
)	O
,	O
the	O
default	O
format	O
for	O
saving	O
pages	O
is	O
MHTML	B-Application
.	O
</s>
<s>
The	O
initial	O
release	O
of	O
the	O
new	O
Webkit/Blink	O
-based	O
Opera	B-Application
(	O
Opera	B-Application
15	O
)	O
did	O
not	O
support	O
MHTML	B-Application
,	O
but	O
subsequent	O
releases	O
(	O
Opera	B-Application
16	O
onwards	O
)	O
do	O
.	O
</s>
<s>
MHTML	B-Application
can	O
be	O
enabled	O
by	O
typing	O
"	O
opera://flags	O
#save	O
-page-as-mhtml	O
"	O
at	O
the	O
address	O
bar	O
.	O
</s>
<s>
Creating	O
MHTML	B-Application
files	O
in	O
Google	B-Application
Chrome	I-Application
is	O
enabled	O
by	O
default	O
in	O
version	O
86	O
.	O
</s>
<s>
Creating	O
MHTML	B-Application
(	O
multipart/related	O
)	O
files	O
in	O
Yandex	O
Browser	B-Application
is	O
enabled	O
by	O
default	O
in	O
version	O
22.7.4.960	O
(	O
July	O
2022	O
)	O
.	O
</s>
<s>
Similarly	O
to	O
Google	B-Application
Chrome	I-Application
,	O
the	O
Chromium-based	O
Vivaldi	B-Language
browser	I-Language
can	O
save	O
webpages	O
as	O
MHTML	B-Application
files	O
since	O
the	O
2.3	O
release	O
.	O
</s>
<s>
It	O
supports	O
both	O
reading	O
and	O
writing	O
MHTML	B-Application
files	O
by	O
toggling	O
the	O
"	O
vivaldi://flags/	O
#save	O
-page-as-mhtml	O
"	O
option	O
.	O
</s>
<s>
Mozilla	B-Application
Firefox	I-Application
does	O
not	O
support	O
MHTML	B-Application
.	O
</s>
<s>
Until	O
the	O
advent	O
of	O
version	O
57	O
(	O
"	O
Firefox	B-Application
Quantum	O
"	O
)	O
,	O
MHT	O
files	O
could	O
be	O
read	O
and	O
written	O
by	O
installing	O
a	O
browser	B-Protocol
extension	I-Protocol
,	O
such	O
as	O
Mozilla	B-Operating_System
Archive	I-Operating_System
Format	I-Operating_System
or	O
UnMHT	O
.	O
</s>
<s>
From	O
version	O
3.1.1	O
onwards	O
,	O
Apple	O
Inc.	O
'	O
s	O
Safari	B-Application
web	I-Application
browser	I-Application
does	O
not	O
natively	O
support	O
the	O
MHTML	B-Application
format	O
.	O
</s>
<s>
Instead	O
,	O
Safari	B-Application
supports	O
the	O
webarchive	B-Application
format	O
,	O
and	O
the	O
macOS	B-Application
version	O
includes	O
a	O
print-to-PDF	O
feature	O
.	O
</s>
<s>
As	O
with	O
most	O
other	O
modern	O
web	B-Application
browsers	I-Application
,	O
support	O
for	O
MHTML	B-Application
files	O
can	O
be	O
added	O
to	O
Safari	B-Application
via	O
various	O
third-party	O
extensions	O
.	O
</s>
<s>
As	O
of	O
version	O
3.5.7	O
,	O
KDE	B-Application
's	O
Konqueror	B-Application
web	B-Application
browser	I-Application
does	O
not	O
support	O
MHTML	B-Application
files	O
.	O
</s>
<s>
An	O
extension	O
project	O
,	O
mhtconv	O
,	O
can	O
be	O
used	O
to	O
allow	O
saving	O
and	O
viewing	O
of	O
MHTML	B-Application
files	O
.	O
</s>
<s>
NetFront	B-Operating_System
3.4	O
(	O
on	O
devices	O
such	O
as	O
the	O
Sony	B-Device
Ericsson	I-Device
K850	I-Device
)	O
can	O
view	O
and	O
save	O
MHTML	B-Application
files	O
.	O
</s>
<s>
Pale	B-Protocol
Moon	I-Protocol
requires	O
an	O
extension	O
to	O
be	O
installed	O
to	O
read	O
and	O
write	O
MHT	O
files	O
.	O
</s>
<s>
One	O
extension	O
is	O
freely	O
available	O
,	O
MozArchiver	O
,	O
a	O
fork	O
of	O
Mozilla	B-Operating_System
Archive	I-Operating_System
Format	I-Operating_System
extension	O
.	O
</s>
<s>
GNOME	B-Language
Web	I-Language
added	O
support	O
for	O
read	O
and	O
save	O
web	O
pages	O
in	O
MHTML	B-Application
since	O
version	O
3.14.1	O
released	O
in	O
September	O
2014	O
.	O
</s>
<s>
There	O
are	O
commercial	O
software	O
products	O
for	O
viewing	O
MHTML	B-Application
files	O
and	O
converting	O
them	O
to	O
other	O
formats	O
,	O
such	O
as	O
PDF	B-Application
and	O
ePub	O
.	O
</s>
<s>
Some	O
HTML	B-General_Concept
editor	I-General_Concept
programs	O
can	O
view	O
and	O
edit	O
MHTML	B-Application
files	O
.	O
</s>
<s>
MIME	B-Application
type	I-Application
for	O
MHTML	B-Application
is	O
not	O
well	O
agreed	O
upon	O
.	O
</s>
<s>
Used	O
MIME	B-Application
types	I-Application
include	O
:	O
</s>
<s>
The	O
"	O
Save	O
to	O
Google	O
Drive	O
"	O
extension	O
for	O
Google	B-Application
Chrome	I-Application
can	O
save	O
as	O
MHTML	B-Application
as	O
one	O
of	O
its	O
outputs	O
.	O
</s>
<s>
Microsoft	B-Application
OneNote	I-Application
,	O
starting	O
with	O
OneNote	B-Application
2010	O
,	O
emails	O
individual	O
pages	O
as	O
.mht	B-Application
files	O
.	O
</s>
<s>
Evernote	B-Application
for	O
Windows	O
can	O
export	O
notes	O
as	O
MHT	O
format	O
,	O
as	O
an	O
alternative	O
to	O
HTML	B-Language
or	O
its	O
own	O
native	O
.enex	O
format	O
.	O
</s>
<s>
In	O
May	O
2015	O
,	O
a	O
researcher	O
noted	O
that	O
attackers	O
could	O
build	O
malicious	O
documents	O
by	O
creating	O
an	O
MHT	O
file	O
,	O
appending	O
an	O
MSO	O
object	O
at	O
the	O
end	O
(	O
MSO	O
is	O
a	O
file	O
format	O
used	O
by	O
the	O
Microsoft	B-Application
Outlook	I-Application
e-mail	O
application	O
)	O
,	O
and	O
renaming	O
the	O
resulting	O
file	O
with	O
a	O
.doc	O
extension	O
.	O
</s>
<s>
In	O
April	O
2019	O
,	O
a	O
security	O
researcher	O
published	O
details	O
about	O
an	O
XML	O
external	O
entity	O
(	O
XXE	B-Protocol
)	O
vulnerability	O
that	O
could	O
be	O
exploited	O
when	O
a	O
user	O
opens	O
an	O
MHT	O
file	O
.	O
</s>
<s>
Since	O
the	O
Windows	O
operating	O
system	O
is	O
set	O
to	O
automatically	O
open	O
all	O
MHT	O
files	O
,	O
by	O
default	O
,	O
in	O
Internet	B-Application
Explorer	I-Application
,	O
the	O
exploit	O
could	O
be	O
triggered	O
when	O
a	O
user	O
double-clicked	O
on	O
a	O
file	O
that	O
they	O
received	O
via	O
email	O
,	O
instant	O
messaging	O
,	O
or	O
another	O
vector	O
,	O
including	O
a	O
different	O
browser	B-Application
.	O
</s>
<s>
The	O
data	B-Protocol
URI	I-Protocol
scheme	I-Protocol
offers	O
an	O
alternative	O
for	O
including	O
separate	O
elements	O
such	O
as	O
images	O
,	O
style-sheets	O
and	O
scripts	O
in-line	O
when	O
serving	O
an	O
HTML	B-Language
request	O
or	O
saving	O
an	O
HTML	B-Language
resource	O
for	O
offline	O
use	O
.	O
</s>
<s>
Like	O
the	O
embedded	O
content	O
within	O
MHTML	B-Application
,	O
data	B-Protocol
URIs	I-Protocol
use	O
Base64	B-Protocol
encoding	I-Protocol
of	O
the	O
external	O
resources	O
(	O
which	O
may	O
be	O
binary	O
or	O
text	O
)	O
to	O
embed	O
them	O
in-line	O
within	O
the	O
HTML	B-Language
markup	O
.	O
</s>
<s>
HTML	B-Language
pages	O
saved	O
with	O
external	O
elements	O
embedded	O
using	O
the	O
data	B-Protocol
URI	I-Protocol
scheme	I-Protocol
are	O
standard	O
web	O
pages	O
,	O
and	O
can	O
be	O
opened	O
by	O
any	O
modern	O
browser	B-Application
,	O
including	O
browsers	B-Application
not	O
supporting	O
MHTML	B-Application
such	O
as	O
Mozilla	B-Application
Firefox	I-Application
.	O
</s>
<s>
Unlike	O
MHTML	B-Application
,	O
saving	O
web	O
pages	O
with	O
their	O
external	O
resources	O
embedded	O
using	O
data	B-Protocol
URIs	I-Protocol
requires	O
a	O
third-party	O
extension	O
to	O
be	O
installed	O
in	O
the	O
browser	B-Application
.	O
</s>
<s>
The	O
Mozilla	B-Operating_System
Archive	I-Operating_System
Format	I-Operating_System
(	O
MAFF	O
)	O
is	O
a	O
legacy	O
Web	B-General_Concept
archive	I-General_Concept
file	I-General_Concept
format	O
that	O
was	O
supported	O
by	O
Firefox	B-Application
from	O
2004	O
to	O
2018	O
through	O
an	O
add-on	O
.	O
</s>
<s>
Unlike	O
both	O
MHTML	B-Application
and	O
data	B-Protocol
URIs	I-Protocol
,	O
MAFF	O
uses	O
a	O
ZIP	B-General_Concept
container	O
to	O
preserve	O
both	O
the	O
HTML	B-Language
file	I-Language
and	O
its	O
external	O
elements	O
.	O
</s>
<s>
In	O
October	O
2017	O
the	O
add-on	O
developer	O
announced	O
the	O
format	O
would	O
no	O
longer	O
be	O
supported	O
in	O
future	O
versions	O
of	O
Firefox	B-Application
.	O
</s>
