Many states have laws requiring voters to show some form of identification at the polls, and the majority of these voter identification laws are currently in force.
But these voter ID laws vary from state to state. Some require photo identification (like a driver’s license or military ID), while others accept other forms of non-photo identification (such as a bank statement).
The laws also differ when it comes to how strict they are, and what happens to voters who can’t produce the requested ID. States with strict voter ID laws require voters who don’t have ID to vote using a provisional ballot and then take additional steps after Election Day (for example, returning to the election office with an ID) to ensure that their votes are counted. States with non-strict voter ID laws may let a person vote if he or she signs an affidavit certifying identity, or may allow election workers to verify whether the person was registered, without the voter having to take any further action.
Ballatopedia is one good resource for a regularly updated list and map of state voter ID laws.