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

Answer 2

There is simple way to use cross-domain anything, just create simple page that will be included as proxy iframe hosted on domain you try to access, send PostMessage to that iframe and inside iframe you do your LocalStorage database manipulation. Here is a link to article that do this with lcoalStorage. And here is demo that send message to different page in subdomain check the source code, it use iframe and PostMessage.

EDIT: New version of sysend.js library (used by above demo) use BroadcastChannel if browser support it, but still it require Iframe. Recent version also simplify using of Cross-Origin messages, you have html of the iframe in repo, that you can use (or you can use simple html file with single script tag with the lib) and in parent you just need to call one function sysend.proxy('https://example.com'); where example.com need to have proxy.html file (you can also use your own filename and different path).