Greasemonkey Storage

Question

Is there any limit on how much data can be stored using GM_setValue?

Answer 1

GM stores it in properties. Open about:config and look for them.

According to http://diveintogreasemonkey.org/api/gm_getvalue.html, you can find them in the greasemonkey.scriptvals branch.

This sqlite info on its limits shows some default limits for strings and blobs, but they may be changed by Firefox.

Answer 2

According to the site you provided, "The value argument can be a string, boolean, or integer."

Obviously, a string can hold far more information than an integer or boolean.

Since GreaseMonkey scripts are JavaScript, the max length for a GM_setValue is the max length of a JavaScript string. Actually, the JavaScript engine (browser specific) determines the max length of a string.

I do not know any specifics, but you could write a script to determine max length.

Keep doubling length until you get an error. Then, try a value halfway between maxGoodLen and minBadLen until maxGoodLen = maxBadLen - 1.

Answer 3

More information is in the Greasespot Wiki:

The Firefox preference store is not designed for storing large amounts of data. There are no hard limits, but very large amounts of data may cause Firefox to consume more memory and/or run more slowly.[2]

The link refers to a discussion in the Greasemonkey Mailinglist. Anthony Lieuallen answers the same question as you posted:

I've just tested this. Running up to a 32 meg string seems to work without major issues, but 64 or 128 starts to thrash the disk for virtual memory a fair deal.