The IDB spec http://dvcs.w3.org/hg/IndexedDB/raw-file/tip/Overview.html says: Transaction lifecycle: "Transactions have an active flag, which determines if new requests can be made against the transaction." "When a transaction is created its active flag is initially set to true." - i.e. right after the db.transaction() call "The implementation must allow requests to be placed against the transaction whenever the active flag is true." "Requests may be placed against a transaction only while that transaction is active. If an attempt is made to place a request against a transaction when that transaction is not active, the implementation must reject the attempt by throwing a DOMException of type TransactionInactiveError." Version changes: "This transaction will be active inside the onupgradeneeded event handler, allowing the creation of new object stores and indexes." Abort: "Otherwise this method sets the transaction's active flag to false..." Transaction creation: "When control is returned to the event loop, the implementation must set the active flag to false." Firing events: ... "Set the active flag of transaction to true." ... "Set the active flag of transaction to false." ... Right now we don't have a notion of non-active transaction - until it is |finished| we allow requests to be placed against it.