Question

Is it possible to store data across domains using a Greasemonkey script? I want to allow a Javascript object to be accessed from multiple websites that are using the same Greasemonkey script.

Answer 1

Yes, that is one of the purposes of GM_setvalue(), it stores data, per script, and across domains.

Beware that the bog-standard GM_setValue() is somewhat problematic. It can use lots of global resources or cause a script instance to crash.

Here are some guidelines:

1. Do not use GM_setValue() to store anything but strings. For anything else, use a serializer such as GM_SuperValue. Even innocent looking integers can cause the default GM_setValue() to crash.

2. Rather than store lots of small variables, it may be better to wrap them in an object and store that with one of the serializers.

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Finally note that localStorage has a specific meaning in javascript, and localStorage is domain specific.