Can HTML5 databases and localStorage be shared across subdomains?

Question

I am attempting to share data across subdomains using Safari. I would like to use an HTML5 database (specifically localStorage as my data is nothing but key-value pairs). However, it seems as though data stored to domain.com can not be accessed from sub.domain.com (or vice versa). Is there any way to share a single database in this situation?

Answer 1

Update 2016

This library from Zendesk worked for me.

Sample:

Hub

// Config s.t. subdomains can get, but only the root domain can set and del
CrossStorageHub.init([
  {origin: /\.example.com$/,            allow: ['get']},
  {origin: /:\/\/(www\.)?example.com$/, allow: ['get', 'set', 'del']}
]);

Note the $ for matching the end of the string. The regular expression in the above example will match origins such as valid.example.com, but not invalid.example.com.malicious.com.

Client

var storage = new CrossStorageClient('https://store.example.com/hub.html');

storage.onConnect().then(function() {
  return storage.set('newKey', 'foobar');
}).then(function() {
  return storage.get('existingKey', 'newKey');
}).then(function(res) {
  console.log(res.length); // 2
}).catch(function(err) {
  // Handle error
});

Check https://stackoverflow.com/a/39788742/5064633