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feature: localStorage status: use tags: gtie7 kind: api polyfillurls:Remy’s storage polyfill, sessionstorage

Local and session storage are a great way to store data without resorting to cookies. IE8 supported localStorage and sessionStorage so you may not need a polyfill. If you do, Remy's is a piece of cake to implement and use.

This is a simple key/value store, so if you want to store complex data use JSON.parse(str) and JSON.stringify(obj) on your way in and out. There is also no way to know if you exceeded the storage cross-browser, so wrap your store commands in try/catch. Up to 2.5MB is safe to use.

As part of keeping things simple, localStorage has a synchronous API that runs on the main UI thread in browsers; as a consequence of that, a race condition can occur if a user has the same site open in multiple windows or tabs running as separate processes. For many applications, that’s never really a problem in practice. But it can cause data corruption—so applications where it’s important to try to ensure that absolutely no data corruption can occur should instead use a more robust storage mechanism such as IndexedDB.

Due to the shortcomings of localStorage, there are calls to stop advocating for and building examples that use it.