Question: I'm trying to use chrome storage in an extension, via a content\_script, but I keep failing on 

```
Uncaught TypeError: Cannot read property 'sync' of undefined 

```

This is my code:

```
testChromeStorage();

function testChromeStorage() {  
    console.log("Saving");
    chrome.storage.sync.set({'value': theValue}, function() {
        message('Settings saved');
    });
    chrome.storage.sync.get("value", function (retVal) {
            console.log("Got it? " + retVal.value);
    });
}

```

Answer: 
If someone was facing this issue on Firefox, please note, that it is not supported yet:

<https://developer.mozilla.org/en-US/Add-ons/WebExtensions/API/storage#Chrome_incompatibilities>

For my purposes it was sufficient to replace `chrome.storage.sync` by `chrome.storage.local`.

Regarding the Firefox implementation state it might be worth to look also here from time to time:

<https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions/Browser_support_for_JavaScript_APIs#storage>
See <https://developer.chrome.com/extensions/content_scripts.html>:

> 
> However, content scripts have some limitations. They cannot:
> 
> 
> *Use chrome.* APIs (except for parts of chrome.extension)\*
> 
> 
> 

(emphasis added)