What is conditional/ validation request

The HTTP Specification has concept of conditional/ validation request, which client makes to check if the cached copy that it has is still valid. Client will make the conditional get request in two cases

  • Resource is not cacheable: If it made a request for resource and got the response, but request does not have either Expires or cache-control header or you explicitly set the resource as non-cachable by setting Expires equal to 0 or in the past date, or set Cache-control: no-cache.

  • Cached resource is expired: A resource is cachable and lets say it was cacheable till 1 PM on 1st of August 2010, then if you query for the resource at 1.30 pm, in that case browser/ cache will make a request



When a browser makes conditional request either of two things will happen

  • Client copy is fresh: That means the copy that browser has is same as that of the copy of the server or the resource is not modified. In that case the server sends HTTP status code 304 (Not modified) with only headers without body. The server can send new expires date for the resource so that the resource can get cached in the browser

  • Client copy is stale: Means the server has new copy of the resource, or the resource has changed since the last time user requested for it. In that case the server will return HTTP status code 200 OK, with full resource in the body.



Conditional requests are implemented by conditional headers that start with If. The conditional header allows method to execute only if particular conditional is met

GET /perf/images/cachesample.gif HTTP/1.0
If-Modified-Since Thu, 22 Jul 2010 23:41:23 GMT


Means return /perf/images/cachesample.gif, only if it was modified since 22nd of July

There are two different attributes that you can use for testing creating conditional request

  • Last Modified date: Means check if the document has changed since the last modified date

  • ETag: Used to check if the entity tag(ETag) of the document has changed

3 comments:

srjwebsolutions said...


We are leading responsive website designing and development company in Noida.
We are offering mobile friendly responsive website designing, website development, e-commerce website, seo service and sem services in Noida.

Responsive Website Designing Company in Noida
Website Designing Company in Noida
SEO Services in Noida
SMO Services in Noida

Vikas Chaudhary said...

Battery Mantra is Authorized exide car battery dealer in Noida and Greater Noida. We are providing our service in Indirapuram, Delhi, Ashok Nagar.

Exide Battery Dealer in Noida
Battery Dealer in Noida
Authorized Battery Dealer in Noida
Car Battery Dealer in Noida
Car Battery Dealer
Exide Battery Dealer

EG MEDI said...

Egmedi.com is online medical store pharmacy in laxmi nagar Delhi. You can Order prescription/OTC medicines online.
Cash on Delivery available. Free Home Delivery


Online Pharmacy in Delhi
Buy Online medicine in Delhi
Online Pharmacy in laxmi nagar
Buy Online medicine in laxmi nagar
Onine Medical Store in Delhi
Online Medical store in laxmi nagar
Online medicine store in delhi
online medicine store in laxmi nagar
Purchase Medicine Online
Online Pharmacy India
Online Medical Store