Instead of doing var request = mozIndexedDB.open("databasename"); request.onsuccess = function(event) { request = event.target.result.setVersion(N); reques

Instead of doing var request = mozIndexedDB.open("databasename"); request.onsuccess = function(event) { request = event.target.result.setVersion(N); request.onsuccess = function(event) { // set up your database } } it looks like var request = mozIndexedDB.open("databasename", N); request.onupgradeneeded = function(event) { // set up your database } request.onsuccess = function(event) { // do stuff with your database } Feel free to email me at <my hacker news username>@mozilla.com if you need a more detailed explanation.