The federal government is making four free at-home COVID-19 tests available for order beginning this week.

Each home in the U.S. is eligible to order the tests without charge through the website COVIDtests.gov. The orders are being processed and delivered by the U.S. Postal Service.

Orders will usually ship in 7-12 days, according to government officials. The formal launch day was Wednesday, but the online order website was released a day early in beta test mode.

President Biden announced his plan to make half a billion of the tests available to Americans by mail last month ahead of Christmas just as the omicron variant was surging across the nation. The Biden administration has pledged to acquire 1 billion rapid tests, with 500 million to be distributed by mail and the other 500 million ready to meet future demand.

According to the Centers for Disease Control and Prevention, or CDC, the variant makes up 99.5% of new coronavirus cases as of last week.

The U.S. is currently averaging 777,453 new COVID-19 cases and 1,797 new deaths per day, according to data from Johns Hopkins University.

The COVID-19 tests are rapid antigen at-home tests, not the PCR version. The mail-order tests can be taken anywhere, with results available within 30 minutes. No lab drop-off is required. Officials said the test work whether or not you have COVID-19 symptoms and regardless of whether you are up to date on your COVID vaccines.

The online test instructions state that it is advisable to take an at-home test if you begin having COVID-19 symptoms such as a fever, sore throat, runny nose, or a loss of taste or smell. It is also advisable to take the test if you have come into close contact with someone who exhibits COVID-19 symptoms within at least five days, or when you’re going to gather with a group of people, especially those who are at risk of severe disease or may not be up to date on their COVID-19 vaccines.

If you test positive on your at-home test, you are asked to follow the latest CDC guidance for isolation.