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Editorial Team
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Asked: 2026-05-21T20:46:16+00:00

Writing and reading from LocalStorage is working fine from my popup and tab. However,

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Writing and reading from LocalStorage is working fine from my popup and tab. However, when I attempt to add a value from my background page, it doesn’t seem to write at all. I’m viewing local storage in Chrome Developer Tools by refreshing and looking for the value to show.

In the following example code for background.html ‘lastId’ is displayed correctly in the alert when a new bookmark is added. However, the value is not stored. Additionally, the request for a known value appears to fail with no alert displaying. (Results are the same attempting both syntaxes shown below.)

<html>
<script>
// Grab the id of newly created bookmarks
chrome.bookmarks.onCreated.addListener(function(id) {
    var lastId = id;
    alert(lastId);
    localStorage['lastId'] = lastId;
            var testvalue = localStorage['309'];
    alert(testvalue);
            localStorage.setItem('lastId', lastId);
    var testvalue2 = localStorage.getItem('309');
    alert(testvalue2);
});
</script>
</html>

I keep thinking I must just be missing some small syntax issue or something but can’t see anything. If my manifest declaration was incorrect I don’t think the alert would work for the id. Stumped…

UPDATE: Turns out that you have to force reload of the extension on updates to background pages since they are persistent in browser memory when opened. That is why my saved code appeared not to work. It wasn’t refreshed and I am duly embarrassed.

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1 Answer

  1. Editorial Team

    Hm, I can think about couple things.

    You say that it works in a tab and a popup. This is very strange because it shouldn’t (if by tab you mean content script). Content scripts are able to access only localStorage that belongs to a site they are injected. Popup, background, option pages, and any othe page from extension’s folder can only access extension’s own localStorage. Those two local storages and completely separated. So maybe you are inspecting wrong localStorage?

    To see extension’s own localStorage you need to inspect background or popup page and check resources tab in the inspector. To inspect site or content script localStorage you need to open regular inspector on the page.

    Second moment is your localStorage assignment might be not what you are expecting.

    If you run:

    var lastId = 5;
localStorage['lastId'] = lastId;

    you will get value 5 assigned to lastId property. So to read written value you need to run:

    alert(localStorage['lastId']); //not localStorage['5']

    If you want to store arrays then you would need to serialize/unserialize them through JSON as localStorage can store only strings.

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