# Need Browser to Not Cache Ajax Image **URL:** \ **Category:** Rails\ **Created:** [July 10, 2008, 9:32am UTC](https://www.ruby-forum.com/t/need-browser-to-not-cache-ajax-image/142673 "2008-07-10T09:32:25Z")\ **Posts on this page:** 3\ **Page:** 1
**Author:** ![Joe\_K](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/5e9695/32.png) [@Joe\_K](https://www.ruby-forum.com/u/Joe_K)\ **Post date:** [July 10, 2008, 9:32am UTC](https://www.ruby-forum.com/t/need-browser-to-not-cache-ajax-image/142673/1 "2008-07-10T09:32:25Z")
I am banging my head against the wall here. I have a gd-generated image that keeps being changed via ajax on my page. Since the image is generated based on querystring parameters (which don’t change) but is based on a model (that is constantly changing), the browser caches the image and you have to do a page refresh to update the image. I have hacked around it by appending a random number to the querystring, but that should make every image be cached to the browser, which I don’t want to do to my clients if I don’t have to (there will be LOTS of images). What I have found online is that I need to change the headers that I am sending out. Here’s what I have and it doesn’t work. I don’t know if the headers aren’t being sent or if I am sending the wrong headers or a sickly combination of the two… headers[‘Cache-Control’] = ‘no-cache, must-revalidate, post-check=0, pre-check=0’ headers[‘Pragma’] = ‘public’ headers[‘Expires’] = “0” send\_data image.jpeg, :type =\> “image/jpeg”, :disposition =\> “inline” #this line works Any help would be greatly appreciated. ---
**Author:** ![Joe\_K](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/5e9695/32.png) [@Joe\_K](https://www.ruby-forum.com/u/Joe_K)\ **Post date:** [July 10, 2008, 2:19pm UTC](https://www.ruby-forum.com/t/need-browser-to-not-cache-ajax-image/142673/2 "2008-07-10T14:19:54Z")
On 10 Jul 2008, at 09:31, Joe K wrote: > and it doesn’t work. I don’t know if the headers aren’t being sent > Any help would be greatly appreciated. > Maybe someone might come up with a header-based solution, but you > could also add an extra parameter with a timestamp to the url (don’t > know if the :with parameter of the Rails Javascript helper will do > here, I tend to write up my own Javascript instead of relying on the > Rails helpers). Rails itself uses a similar solution for the css and > javascript files that are loaded (it adds a timestamp). This would > mean your browser would send out requests like: [http://www.mydomain.com/image?time=20080710141812](http://www.mydomain.com/image?time=20080710141812) [http://www.mydomain.com/image?time=20080710141825](http://www.mydomain.com/image?time=20080710141825) [http://www.mydomain.com/image?time=20080710141845](http://www.mydomain.com/image?time=20080710141845) [http://www.mydomain.com/image?time=20080710141910](http://www.mydomain.com/image?time=20080710141910) … Best regards Peter De Berdt ---
**Author:** ![Joe\_K](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/5e9695/32.png) [@Joe\_K](https://www.ruby-forum.com/u/Joe_K)\ **Post date:** [July 10, 2008, 11:30pm UTC](https://www.ruby-forum.com/t/need-browser-to-not-cache-ajax-image/142673/3 "2008-07-10T23:30:56Z")
Peter, That’s almost exactly what I am doing right now, except I use rand(Time.now.to\_i) rather than a timestamp (in the off chance of more than 1 req/sec). I just don’t like the idea of spamming my customers’ cache with images if I don’t have to. Thank you for your help. On Thu, Jul 10, 2008 at 8:19 AM, Peter De Berdt [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)