I'm working on a web app and I'm having the following problem:
When I go on some page my server sends a response with cache-control: no-cache header.
Then I do some changes (graphql mutations) on that page.
When I go to an other page and then click browser back then my browser reads the outdated "response" from the disk cache instead of sending a request to the server to get the change data.
browser loads response from cache although no-cache header is set
I wondering if there is something missing in my headers telling the browser to not use the disk cache?
Some info:
The browser does not send a request to my server. (So it is not cached somewhere else.)
It is not the back-forward cache. (There is already some logic handling the bfcache.)
I can reproduce it in all my browsers. (e.g. Firefox, Chrome, ...)
When I disable the disk cache in the Firefox settings then it is working correctly. (Now, the bfcache kicks in.)
I also found the following thread. Is there a better solution?
Chrome is caching even with HTTP no-cache headers
I would like to understand a particular browser behavior in regard to the back and forward buttons. I always believed that in a "traditional" navigation, clicking the back and forward buttons caused the page to reload, unless we were just changing the hash on the same page (can't recall now if there are other obvious exceptions).
Lately I've observed a behavior that shattered those believes: changing page caused the browser to save a "snapshot" of the last state the page was before navigating away, so whenever I pressed the back button it would take me to the exact moment I navigated away.
While this can be a very useful behavior the problem is that this way I'm showing the user potentially outdated data.
Same behavior happens if I press the forward button: I will land to the next page I visited at the exact state it was when I pressed the back button.
So I spent a little time and started testing different browsers and different domains using the same application and applying the same conditions to come to the following result:
Chrome 102: this behavior happened when navigating on a public domain on the Internet with Dev Tools closed. Whenever I tried it in localhost or with Dev Tools open the reloading happened.
Safari 15: this behavior happened always, didn't matter wether I was on localhost or I had Dev Tools open.
Opera 88: this behavior happened when navigating on a public domain on the Internet regardless the presence of Dev Tools. When navigating on localhost it reloaded the pages.
Firefox 101 and Edge 102 didn't exhibit this behavior, they simply reloaded the pages when navigating.
Is there any explanation or documentation for this difference of behavior? I tried to search it but nothing meaningful came out, perhaps I'm not using the right words.
Update
I checked headers coming from the responses but I think they're not relevant:
These are localhost's
Connection: keep-alive
Date: Thu, 23 Jun 2022 08:58:01 GMT
ETag: W/"57cf-+fmYAdB1w1b8e3hCMCGT2IIRFCg"
Keep-Alive: timeout=5
For the public domains relevant headers are
cache-control: max-age=0
date: Thu, 23 Jun 2022 10:10:23 GMT
expires: Thu, 23 Jun 2022 10:10:23 GMT
Which tell the browser to not cache the page, and that's why I didn't add them in the original question.
I have set Cache control in my response header as Cache-Control:public, max-age=86400. But when I try to refresh page or open a new tab, it always hits my server. The response status I got is 200, server log is appeared for this request also I checked chrome://cache/ this request is not in the list. I already looked some similar SO questions cache-control not working without etag and why cache-control:max-age don't work?. But still with no luck. Tested on chrome 56.
Chrome disables cache when DevTools is open, or at least it does Chrome 59. Open DevTools, go to Network, uncheck "Disable cache" at the top. Now you should be able to refresh the page and see it in chrome://cache.
Cache control tells your browser (and proxy servers like Squid) what resources it cannot cache. But it does not force your browser to cache a resource.
I recommend to check the error_logs to see if you really go to the backend, or stay in the browser.
In my case, browser gives me 200OK in the console logs but I don't reach the back end according to the error_log ...
Cache-Control response header will not work for page refresh. Try making that request twice without refreshing the page, then you will see it being cached (the request won't reach your server internally).
To achieve what you want you might have to cache your request by accessing localStorage, or just cache it through a back-end caching library.
I have trouble figuring out a cache-control header for delivering files that are used for an HTML5 app that uses the AppCache, which works on all major browsers(Chrome/Safari, Opera, Firefox, IE10).
The problem that I run into, is that when one kind of header works for a certain browser, another one may break completely. For example:
Cache-Control: private
Works fine on Webkit browsers, and they refresh and load updated files and replace them in the cache. However Firefox and IE10 both refuse to load the new files and instead get them from the cache (not appcache!), even though they recognize the updated manifest file.
Cache-Control: no-cache
works fine on webkit browsers also, and also makes Firefox AND IE10 load the new files, instead of loading them from their cache, but breaks offline functionality, since they essentially don't cache (as the header would tell) the files, even though they are explicitly mentioned in the appcache manifest.
Lastly, I tried
Cache-Control: must-revalidate
Which works similarly to no-cache but instead of Firefox and IE10 not retaining the files for offline use it's Webkit that doesn't retain them.
Sending no Cache-Control header yields the same results as private or public, since I assume the browser simply assumes that as the standard way.
So what am I missing? public has the same results as private and setting a max-age is not an option since updates (including Hotfixes) are not delivered on a regular basis, but instead whenever they are available or needed.
Can someone shed a light on which Cache-Control header is the correct one to use, which will work on all browsers?
Background:
IIS 7
AspNet 3.5 web app
Chrome dev tools lists 98 requests for the home page of the web app (aspx + js + css + images). In following requests, status code is 200 for css/images files. No cache info, browser asks server each time if file has to be updated. OK.
In IIS 7 I set HTTP header for cache control, set to 6 hours for the "ressources" folder. In Chrome, using dev tools, I can see that header is well set in response:
Cache-Control: max-age=21600
But I still get 98 requests... I thought that browser should not request one ressource if its expiration date is not reached, and I was expecting the number of requests to drop...
I got it. Google Chrome ignores the Cache-Control or Expires header if you make a request immediately after another request to the same URI in the same tab (by clicking the refresh button, pressing the F5 key or pressing Command + R). It probably has an algorithm to guess what does the user really want to do.
A way to test the Cache-Control header is to return an HTML document with a link to itself. When clicking the link, Chrome serves the document from the cache. E.g., name the following document self.html:
<!doctype html>
<html lang="en">
<head>
<meta charset="utf-8">
<title>Test Page</title>
</head>
<body>
<p>
Link to the same page.
If correctly cached, a request should not be made
when clicking the link.
</p>
</body>
</html>
Another option is to copy the URL and paste it in the same tab or another tab.
UPDATE: On a Chrome post published on January 26, 2017, it is described what was the previous behavior and how it is changing by doing only revalidation of the main resource, but not of the sub-resources:
Users typically reload either because a page is broken or the content seems stale. The existing reload behavior usually solves broken pages, but stale content is inefficiently addressed by a regular reload, especially on mobile. This feature was originally designed in times when broken pages were quite common, so it was reasonable to address both use cases at once. However, this original concern has now become far less relevant as the quality of web pages has increased. To improve the stale content use case, Chrome now has a simplified reload behavior to only validate the main resource and continue with a regular page load. This new behavior maximizes the reuse of cached resources and results in lower latency, power consumption, and data usage.
In a Facebook post also published on January 26, 2017, it is mentioned that they found a piece of code were Chrome invalidates all cached resources after a POST request:
we found that Chrome would revalidate all resources on pages that were loaded from making a POST request. The Chrome team told us the rationale for this was that POST requests tend to be pages that make a change — like making a purchase or sending an email — and that the user would want to have the most up-to-date page.
It seems this is not the case anymore.
Finally, it is described that Firefox is introducing Cache-Control: immutable to completely stop revalidation of resources:
Firefox implemented a proposal from one of our engineers to add a new cache-control header for some resources in order to tell the browser that this resource should never be revalidated. The idea behind this header is that it's an extra promise from the developer to the browser that this resource will never change during its max-age lifetime. Firefox chose to implement this directive in the form of a cache-control: immutable header.
Chrome appears to be ignoring your Cache-Control settings if you're reloading in the same tab. If you copy the URL to a new tab and load it there, Chrome will respect the cache control tags and reuse the contents from the cache.
As an example I had this Ruby Sinatra app:
#!/usr/bin/env ruby
require 'sinatra'
before do
content_type :txt
end
get '/' do
headers "Cache-Control" => "public, must-revalidate, max-age=3600",
"Expires" => Time.at(Time.now.to_i + (60 * 60)).to_s
"This page rendered at #{Time.now}."
end
When I continuously reloaded it in the same Chrome tab it would display the new time.
This page rendered at 2014-10-08 13:36:46 -0400.
This page rendered at 2014-10-08 13:36:48 -0400.
The headers looked like this:
< HTTP/1.1 200 OK
< Content-Type: text/plain;charset=utf-8
< Cache-Control: public, must-revalidate, max-age=3600
< Expires: 2014-10-08 13:36:46 -0400
< Content-Length: 48
< X-Content-Type-Options: nosniff
< Connection: keep-alive
* Server thin is not blacklisted
< Server: thin
However accessing the same URL, http://localhost:4567/ from multiple new tabs would recycle the previous result from the cache.
After doing some tests with Cache-Control:max-age=xxx:
Pressing reload button: header ignored
Entering same url any tab (current or not): honored
Using JS (window.location.reload()): ignored
Using Developer Tools (with Disable cache unselected) or incognito doesn't affect
So, the best option while developing is put the cursor in the omnibox and press enter instead of refresh button.
Note: a right button click on refresh icon will show refresh options (Normal, Hard, Empty Cache). Incredibly, no one of these affect on these headers.
If Chrome Developer Tools are open (F12), Chrome usually disables caching.
It is controllable in the Developer Tools settings - the Gear icon to the right of the dev-tools top bar.
While this question is old, I wanted to add that if you are developing using a self-signed certificate over https and there is an issue with the certificate then google will not cache the response no matter what cache headers you use.
This is noted in this bug report:
https://bugs.chromium.org/p/chromium/issues/detail?id=110649
This is addition to kievic answer
To force browser to NOT send Cache-Control header in request, open chrome console and type:
location = "https://your.page.com"
To force browser to add this header click "reload" button.
Quite an old question, but I noticed just recently (2020), that Chrome sometimes ignores the Cache-Control headers for my image resources when browsing using an Incognito window.
"Sometimes" because in my case the Cache-Control directive was honored for small images (~60-200KB), but not for larger ones (10MB).
Not using Incognito window resulted in Chrome using the disk cached version even for the large images.
Another tip:
Do not forget to verify "Date" header - if server has incorrect date/time (or is located in another time zone) - Chrome will keep requesting resource again and again.