Maximum item size in IndexedDB
I'm working on a simple web utility that makes use of IndexedDB (similar to a key-value DB) feature of HTML5.
I was looking for but I was unable to know: what is the maximum size I can store in an item?
Answer
I don't think there's a specific limit for a size of a single item, only a global limit.
The rules regarding the global limit have changed since this answer was originally written. The up-to-date docs are on MDN - depending on the available disk space, the "group" limit (for the given domain, including all of its subdomains) can range from 10 MB to 2 GB.
The older answer - obsoleted with the release of Firefox 38 (2015-05), which removed dom.indexedDB.warningQuota:
From an answer by mbrubeck at support.mozilla.com (I've replaced the links he provided with perma-versions):
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 [...]
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.