The Freedom of Information Act (FOIA) is a United States federal law that grants the public access to information possessed by government agencies. Upon written request, U.S. government agencies are required to release information unless it falls under one of nine exemptions listed in the Act. All Executive Branch departments, agencies and offices, federal regulatory agencies and federal corporations are subject to the Freedom of Information Act. However, it does not apply to Congress, federal courts and parts of the Executive Office of the President that serve only to advise and assist the President. The law is enforceable in a court of law.

Anyone can request information, including U.S. citizens, foreign nationals, organizations, associations and universities, and all agency records that were created or obtained by a federal agency can be requested. This includes print documents, photographs, videos, maps, e-mail, and electronic records.  In addition to releasing information upon written request, agencies are required to publish instructions on how to make a FOIA request and automatically publish certain information in online 'reading rooms.' This information includes records that affect the public, such as regulations, policy statements and staff instructions, as well as information that is or is likely to be frequently requested by the public.

While any information can be requested, government agencies can withhold information that it determines falls under one of nine categories that is exempt under FOI. These categories, as outlined by the Electronic Frontier Foundation, are as follows:

• Classified information that would damage national security

• Internal information involving personnel rules and agency practices

• Material specifically shielded from disclosure by another law

• Confidential commercial or financial data, like trade secrets

• Records that would be privileged in litigation

• Information that would invade someone’s privacy

• Law enforcement records

• Information related to government regulation of financial institutions

• Certain geological/geographical data