expiry header : Java Glossary

home page go to the Java Glossary Home go to the Computer Buyer’s Glossary up jump to foot of page Google search web for more information on this topic Pinterest pin button
* 0-9 A B C D E F G H I J K L M N O P Q R S T U V W X Y Z (all)
©1996-2017 Roedy Green of Canadian Mind Products

expiry header
In the header of every HTTP (Hypertext Transfer Protocol) document served is an expiry field. It tells caching software on the net how long this document will remain fresh. If it has a long expiry date, there is a better chance it can be found in a cache somewhere. Then it can be retrieved rapidly without pestering your server. On the other hand, if you change the document, all the old copies is cache won’t be flushed until the expiry date has passed.

If you are sitting at a browser, sometimes hitting Shift-Reload or Ctrl-Reload will force getting a fresh copy.

If you always rename images or zip files when you change them, you can safely give them a very long expiry date, e.g. three months.

Unfortunately you can’t specify the expiry date in your HTML (Hypertext Markup Language). Your ISP (Internet Service Provider) needs to apply the expiry date headers based on some sort of rule such as the Apache rule scheme.

When reading files from a website programmatically, you can force a fresh copy rather a faster cached copy with URLConnection.setUseCaches( false ).

This page is posted
on the web at:

 http://mindprod.com/jgloss/expiryheader.html

Optional Replicator mirror
of mindprod.com
on local hard disk J:

 J:\mindprod\jgloss\expiryheader.html
Canadian Mind Products
Please the feedback from other visitors, or your own feedback about the site.
Contact Roedy. Please feel free to link to this page without explicit permission.

IP:[65.110.21.43]
Your face IP:[98.81.24.230]
You are visitor number