How to programmatically empty browser cache?

Question

I am looking for a way to programmatically empty the browser cache. I am doing this because the application caches confidential data and I'd like to remove those when you press "log out". This would happen either via server or JavaScript. Of course, using the software on foreign/public computer is still discouraged as there are more dangers like key loggers that you just can't defeat on software level.

Answer 1

2023 update: See the Clear-Site-Data HTTP header, through which the server can instruct a client web browser to clear the website cache for its domain/subdomain, regardless of earlier Cache-Control headers. Intermediate caches may still have the data cached though and may not respect the header. (thanks, @nishanthshanmugham)

There's no way a browser will let you clear its cache. It would be a huge security issue if that were possible. This could be very easily abused - the minute a browser supports such a "feature" will be the minute I uninstall it from my computer.

What you can do is to tell it not to cache your page, by sending the appropriate headers or using these meta tags:

<meta http-equiv='cache-control' content='no-cache'>
<meta http-equiv='expires' content='0'>
<meta http-equiv='pragma' content='no-cache'>

You might also want to consider turning off auto-complete on form fields, although I'm afraid there's a standard way to do it (see this question).

Regardless, I would like to point out that if you are working with sensitive data you should be using SSL. If you aren't using SSL, anyone with access to the network can sniff network traffic and easily see what your user is seeing.

Using SSL also makes some browsers not use caching unless explicitly told to. See this question.

Answer 2

It's possible, you can simply use jQuery to substitute the 'meta tag' that references the cache status with an event handler / button, and then refresh, easy,

$('.button').click(function() {
    $.ajax({
        url: "",
        context: document.body,
        success: function(s,x){

            $('html[manifest=saveappoffline.appcache]').attr('content', '');
                $(this).html(s);
        }
    }); 
});

NOTE: This solution relies on the Application Cache that is implemented as part of the HTML 5 spec. It also requires server configuration to set up the App Cache manifest. It does not describe a method by which one can clear the 'traditional' browser cache via client- or server-side code, which is nigh impossible to do.

Answer 3

use html itself.There is one trick that can be used.The trick is to append a parameter/string to the file name in the script tag and change it when you file changes.

<script src="myfile.js?version=1.0.0"></script>

The browser interprets the whole string as the file path even though what comes after the "?" are parameters. So wat happens now is that next time when you update your file just change the number in the script tag on your website (Example <script src="myfile.js?version=1.0.1"></script>) and each users browser will see the file has changed and grab a new copy.

Answer 4

The best idea is to make js file generation with name + some hash with version, if you do need to clear cache, just generate new files with new hash, this will trigger browser to load new files

Answer 5

Here is a single-liner of how you can delete ALL browser network cache using Cache.delete()

caches.keys().then((keyList) => Promise.all(keyList.map((key) => caches.delete(key))))

Works on Chrome 40+, Firefox 39+, Opera 27+ and Edge.

Answer 6

On Chrome, you should be able to do this using the benchmarking extension. You need to start your chrome with the following switches:

./chrome --enable-benchmarking --enable-net-benchmarking 

In Chrome's console now you can do the following:

chrome.benchmarking.clearCache();
chrome.benchmarking.clearHostResolverCache();
chrome.benchmarking.clearPredictorCache();
chrome.benchmarking.closeConnections();

As you can tell from above commands, it not only clears the browser cache, but also clears the DNS cache and closes network connections. These are great when you're doing page load time benchmarking. Obviously you don't have to use them all if not needed (e.g. clearCache() should suffice if you need to clear the cache only and don't care about DNS cache and connections).

Answer 7

Initially I tried various programmatic approach in my html, JS to clear browser cache. Nothing works on latest Chrome.

Finally, I ended up with .htaccess:

<IfModule mod_headers.c>
    Header set Cache-Control "no-cache, no-store, must-revalidate"
    Header set Pragma "no-cache"
    Header set Expires 0
</IfModule>

Tested in Chrome, Firefox, Opera

Reference: https://wp-mix.com/disable-caching-htaccess/

Answer 8

You could have the server respond with a Clear Site Data directive that instructs the user agent to clear the site's locally stored data.

For example:

Clear-Site-Data: "cache", "cookies", "storage"

That header would instruct the user agent to clear all locally stored data, including:

• Network cache
• User agent caches (like prerendered pages, script caches, etc.)
• Cookies
• HTTP authentication credentials
• Origin-bound tokens (such as Channel ID and Token Binding)
• Local storage
• Session storage
• IndexedDB
• Web SQL database
• Service Worker registrations

You can send the request using fetch() and do location.reload() afterwards to get a fresh restart.

Answer 9

location.reload(true); will hard reload the current page, ignoring the cache.
Cache.delete() can also be used for new chrome, firefox and opera.

Answer 10

You can now use Cache.delete()

Example:

let id = "your-cache-id";
// you can find the id by going to 
// application>storage>cache storage 
// (minus the page url at the end)
// in your chrome developer console 

caches.open(id)
.then(cache => cache.keys()
  .then(keys => {
    for (let key of keys) {
      cache.delete(key)
    }
  }));

Works on Chrome 40+, Firefox 39+, Opera 27+ and Edge.

Answer 11

//The code below should be put in the "js" folder with the name "clear-browser-cache.js"

(function () {
    var process_scripts = false;
    var rep = /.*\?.*/,
    links = document.getElementsByTagName('link'),
    scripts = document.getElementsByTagName('script');
    var value = document.getElementsByName('clear-browser-cache');
    for (var i = 0; i < value.length; i++) {
        var val = value[i],
            outerHTML = val.outerHTML;
        var check = /.*value="true".*/;
        if (check.test(outerHTML)) {
            process_scripts = true;
        }
    }
    for (var i = 0; i < links.length; i++) {
        var link = links[i],
        href = link.href;
        if (rep.test(href)) {
            link.href = href + '&' + Date.now();
        }
        else {
            link.href = href + '?' + Date.now();
        }
    }
    if (process_scripts) {
        for (var i = 0; i < scripts.length; i++) {
            var script = scripts[i],
            src = script.src;
            if (src !== "") {
                if (rep.test(src)) {
                    script.src = src + '&' + Date.now();
                }
                else {
                    script.src = src + '?' + Date.now();
                }
            }
        }
    }
})();

At the end of the tah head, place the line at the code below

    < script name="clear-browser-cache" src='js/clear-browser-cache.js' value="true" >< /script >

Answer 12

By definining a function for cache invalidate meta tags:

function addMetaTag(name,content){
var meta = document.createElement('meta');
meta.httpEquiv = name;
meta.content = content;
document.getElementsByTagName('head')[0].appendChild(meta);
}

You can call:

addMetaTag("pragma","no-cache")
addMetaTag("expires","0")
addMetaTag("cache-control","no-cache")

That will insert meta tags for subsequents requests, which will force browser to fetch fresh content. After inserting, you can call location.reload() and this will work in mostly all browsers (Cache.delete() is not working at chrome for ex.)

Answer 13

I clear the browser's cache for development reasons. Clearing local storage, session storage, IndexDB, cookies, etc. when the data schema changes. If not cleared, there could be data corruption when syncing data with the database. Cache could also be cleared for security reasons as the OP suggested.

This is the code I use:

caches.keys().then(list => list.map(key => caches.delete(key)))

Simple as that, works like a charm. For more information:

https://developer.mozilla.org/en-US/docs/Web/API/Cache

Answer 14

Imagine the .js files are placed in /my-site/some/path/ui/js/myfile.js

So normally the script tag would look like:

<script src="/my-site/some/path/ui/js/myfile.js"></script>

Now change that to:

<script src="/my-site/some/path/ui-1111111111/js/myfile.js"></script>

Now of course that will not work. To make it work you need to add one or a few lines to your .htaccess The important line is: (entire .htaccess at the bottom)

RewriteRule ^my-site\/(.*)\/ui\-([0-9]+)\/(.*) my-site/$1/ui/$3 [L]

So what this does is, it kind of removes the 1111111111 from the path and links to the correct path.

So now if you make changes you just have to change the number 1111111111 to whatever number you want. And however you include your files you can set that number via a timestamp when the js-file has last been modified. So cache will work normally if the number does not change. If it changes it will serve the new file (YES ALWAYS) because the browser get's a complete new URL and just believes that file is so new he must go get it.

You can use this for CSS, favicons and what ever gets cached. For CSS just use like so

<link href="http://my-domain.com/my-site/some/path/ui-1492513798/css/page.css" type="text/css" rel="stylesheet">

And it will work! Simple to update, simple to maintain.

The promised full .htaccess

If you have no .htaccess yet this is the minimum you need to have there:

<IfModule mod_rewrite.c>
    RewriteEngine On
    RewriteBase /

    RewriteRule ^my-site\/(.*)\/ui\-([0-9]+)\/(.*) my-site/$1/ui/$3 [L]
</IfModule>