Best way to implement offline storage for web application (work on all browser + tablets )

I wonder about the best way to implement offline possiblities for a web application. I have searched the web but couldn't figured out what currently the best way is to create a web application offline (and will work in the future)

The lay-out of the web application i can save with Offline Application Caching...

But the problem is that i have a lot of key-value data开发者_如何转开发 that i need to store offline. With localStorage, sessionStorage the limit to save data offline is 5MB...And that's not enough...

I seach for the following things:

• Gears from Google: not supported anymore
• Web SQl database: not supported anymore
• IndexedDb HTML5: not supported by all browsers (only chrome and firefox). I think this is currently the best way...

Is it possible to increase the Offline Application Caching and save the key-value data in a text format witch offline application caching??

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https://github.com/marcuswestin/store.js is mature (~2 years), still updated and works in an amazing array of browsers.