By default in Firefox 4, a site can use up to 50MB of IndexedDB storage. If it tries to use more than 50MB, Firefox will ask the user for permission: http://mxr.mozilla.org/mozilla-central/source/modules/libpref/src/init/all.js#101

In Firefox for mobile devices (Google Android and Nokia Maemo), Firefox will ask for permission if a site tries to use more than 5MB: http://mxr.mozilla.org/mozilla-central/source/mobile/app/mobile.js#571

Thanks, this is great to know. A few more questions, if possible.

Will Firefox ask for permission if a site tries to use more than 5MB of "LocalStorage API"? Or is LocalStorage API strictly restricted to 5MB?

What are the maximum limits of local storage and indexDB storage, after getting all the permissions ? Can I put 4 gig in localstorage? in indexDB?

Thanks again for the great info! David

If the user grants permission for a site to exceed the 50 MB IndexedDB quota, then as far as I know Firefox does not impose any more limits. The only limits on the size of the IndexedDB database will be the user's disk space and operating system.

The localStorage quota is 5000KB, and there is no way for a web site to ask the browser for permission to store more than that amount in localStorage.

Hello, I'm using indexedDB, and when store more then 50mb, after that can't delete or clear that object store, just got an error without any more information why is error ocured.

neemanjabuge started a thread here:
https://support.mozilla.com/en-US/questions/837358