This tutorial covers the basic concepts of html5 application cache manifest and it's types such as cache manifest., network and fallback.
HTML5 application cache manifest and its types
Basics of html cache manifest
For caching the web page,
it is mandatory to declare the manifest with html element on every and each
page. A particular webpage can’t be cached until we don’t declare the manifest
file.
The recommend file
extension for a manifest file is appcache. The manifest file also
needs to configure with the correct MIME-type, which must be configured well on
the web server. The format may has follows: text/cache-manifest.
What
is HTML5 Manifest?
It’s a simple text file,
which tells the browser for particular cache processing. In details we can say it
sends a command to browser for specific file type to be stored in the cache.
We can also send a denying
command, if we have to tell the browser that a specific file shouldn’t be store
in the cache
Html
5 manifest types
The Manifest file has been
defined in three particular types. You can also say a Manifest file can contain
three sections in it. Here are the details of three sections or types:
• Cache Manifest
• Network
• Fallback
Cache
Manifest
The files listed under
this category only will be cached after they are downloaded for first time. To
declare the cache manifest type, you need to write CACHE MANIFEST at the first
line of the page.
Cache Manifest: Syntax
CACHE
MANIFEST
/theme.css
/logo.gif
/main.js
In the above demonstrated
syntax, there are three types of file have been declared: CSS file, GIF file
and JS file. When the user will use the internet connection for the first time,
these three files will be download. And once the download is finished, the user
can access these files, even when no internet connections.
Network
The files listed under
this category will always require an internet connection. Without the internet
connection these files will not be served.
Often we have seen that we
include some PHP files or other resources to get access in the database. To do
this such event, we authorize the user with login system. In the section of
Manifest type, we can prevent the user for accessing the particular file as
cached version.
Network: Syntax
NETWORK:
login.php
Instead of declaring a
specific file, we can also use an asterisk sign to prevent all resources to be
cached. And user must have an internet connection to get access.
Fallback
This section of Manifest
can be used if we want to serve a specific file in case of no internet
connection. In this process we create a specific file and set it in the
fallback. Once the user is offline or not able to access the internet
connection. The specified file will be served.
Fallback: Syntax
FALLBACK:
/html/
/offline_backup.html
Conclusion
This seems good if someone
has issue with internet connection, but be careful what you cache. Once the
browser cache the file, the user will continue seeing the cached version until
you don’t change your updates with program or the user doesn’t clear the cache
of the browser.
COMMENTS