This add-on uses the existing built in dictionary and word suggestion algorithm. This add-on is not intended to replace the existing spell checker but rather to make it easier to check several words at once. To check spelling with SpellBound, you can use the "Spell Check with SpellBound" option in the drop down context menu after right clicking in the text field, or you can add the "Spell" button to your toolbar with the Firefox customize toolbar window and use it. You may also use the keyboard shortcut that is set to "Ctrl+Shift+F7" by default. This add-on will set in-line spell checking on for single line fields as the default behavior.