title: HTML5 offline storage. File storage? Directories and filesystem API
body: <p>For storing data offline WebApp can use:</p>
  
  <ul>
  <li>session storage, "advanced version of cookies"</li>
  <li>key/value based <a href="http://dev.w3.org/html5/webstorage/" rel="nofollow noreferrer">Web Storage</a> (AKA local/global/offline/DOM storage)</li>
  <li>sql-based <a href="http://dev.w3.org/html5/webdatabase/" rel="nofollow noreferrer">Web SQL Database</a> (deprecated) and <a href="http://dvcs.w3.org/hg/IndexedDB/raw-file/tip/Overview.html" rel="nofollow noreferrer">Indexed Database API</a></li>
  <li><a href="http://www.w3.org/TR/FileAPI/" rel="nofollow noreferrer">FileReader</a> and <a href="http://www.w3.org/TR/file-writer-api/" rel="nofollow noreferrer">FileWriter API</a> (requires user to select files each time the application loads)</li>
  </ul>
  
  <p>But apparently there is no File Storage. Of course, there  is a <a href="http://www.w3.org/TR/offline-webapps/" rel="nofollow noreferrer">manifest-based caching</a>, but it's just a cache and is not supposed to be used as a user data storage.</p>
  
  <p>Does it mean that the user of WebApp is forced to use some sort of a cloud file storage?</p>
  
  <p>Is there any way to save large files on user's local machine? Or maybe some way to select a local folder web application can use to store user data?</p>
  
  <p><strong>Edit</strong>. Security. HTML5 already has the ability to write big portions of data to user's local machine. I don't see any security issues if a browser will provide another, file-based abstraction to store data. It can be some virtual machine, virtual filesystem, whatever.</p>
  
  <p>Hm, I think, it is possible to write JS filesystem and store it as a blob in SQL...</p>
  
  <p><a href="https://stackoverflow.com/questions/292566/browser-application-local-file-system-access">Similar</a> <a href="https://stackoverflow.com/questions/2376745/does-html5-allow-you-to-interact-with-local-client-files-from-within-a-browser">questions</a>.</p>
  
  <p><strong>Update</strong>:
  Hm... recently I've found  <a href="http://www.chromium.org/developers/web-platform-status" rel="nofollow noreferrer">this</a> and <a href="https://bug-45982-attachments.webkit.org/attachment.cgi?id=70320" rel="nofollow noreferrer">this</a>. Maybe it is what I'm looking for... Yes, it is! See the answer below.</p>