QuotaExceededError: Dom exception 22: An attempt was made to add something to storage that exceeded the quota

Question

Using LocalStorage on iPhone with iOS 7 throws this error. I\'ve been looking around for a resolvant, but considering I\'m not even browsing in private, nothing is relevant.

Answer 1

As already explained in other answers, when in Private Browsing mode Safari will always throw this exception when trying to save data with localStorage.setItem() .

To fix this I wrote a fake localStorage that mimics localStorage, both methods and events.

Fake localStorage: https://gist.github.com/engelfrost/fd707819658f72b42f55

This is probably not a good general solution to the problem. This was a good solution for my scenario, where the alternative would be major re-writes to an already existing application.

Answer 2

I use this simple function, which returns true or false, to test for localStorage availablity:

isLocalStorageNameSupported = function() {
    var testKey = 'test', storage = window.sessionStorage;
    try {
        storage.setItem(testKey, '1');
        storage.removeItem(testKey);
        return true;
    } catch (error) {
        return false;
    }
}

Now you can test for localStorage.setItem() availability before using it. Example:

if ( isLocalStorageNameSupported() ) {
    // can use localStorage.setItem('item','value')
} else {
    // can't use localStorage.setItem('item','value')
}

Answer 3

As mentioned in other answers, you'll always get the QuotaExceededError in Safari Private Browser Mode on both iOS and OS X when localStorage.setItem (or sessionStorage.setItem) is called.

One solution is to do a try/catch or Modernizr check in each instance of using setItem.

However if you want a shim that simply globally stops this error being thrown, to prevent the rest of your JavaScript from breaking, you can use this:

https://gist.github.com/philfreo/68ea3cd980d72383c951

// Safari, in Private Browsing Mode, looks like it supports localStorage but all calls to setItem
// throw QuotaExceededError. We're going to detect this and just silently drop any calls to setItem
// to avoid the entire page breaking, without having to do a check at each usage of Storage.
if (typeof localStorage === 'object') {
    try {
        localStorage.setItem('localStorage', 1);
        localStorage.removeItem('localStorage');
    } catch (e) {
        Storage.prototype._setItem = Storage.prototype.setItem;
        Storage.prototype.setItem = function() {};
        alert('Your web browser does not support storing settings locally. In Safari, the most common cause of this is using "Private Browsing Mode". Some settings may not save or some features may not work properly for you.');
    }
}