Use localStorage across subdomains

javascript, local-storage, subdomain

Solution

This is how I use it across domains...

- Use an iframe from your parent domain - say `parent.example`

- Then on each `child.example` domain, just do a postMessage to your `parent.example` iframe

- All you need to do is setup a protocol of how to interpret your postMessage messages to talk to the `parent.example` iframe.

Problem

I'm replacing cookies with localStorage on browsers that can support it (anyone but IE). The problem is `site.example` and `www.site.example` store their own separate localStorage objects. I believe `www` is considered a subdomain (a stupid decision if you ask me). If a user was originally on `site.example` and decides to type in `www.site.example` on her next visit, all her personal data will be inaccessible. How do I get all my "subdomains" to share the same localStorage as the main domain?

Original source

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