If you are applying for a green card (adjustment of status), naturalization, or some other U.S. immigration benefit, U.S. Citizenship and Immigration Services (USCIS) will require you to submit a fee for "biometrics." It will then call you in for a biometrics appointment, usually a few weeks before you attend the interview at which your application is decided upon (if an interview is required).
Even people who already have a green card, but are applying for a renewal after the card itself expires, must get biometrics done.
In most cases, USCIS requires that people attend their biometrics appointment at a USCIS-authorized "Application Support Center." This is different than the main USCIS office where you will go for your interview for naturalization, adjustment of status, or whatever it is you're applying for.
By the way, this means that if you have questions about your actual immigration case; such as when you are likely to be called in for an interview; this is not the place to ask them. The people who collect biometrics do not have access to your file, and cannot give you advice or information about your case.
For a list of ASCs, see the USCIS Service and Office Locator. In some nonurban areas of the United States, USCIS also offers mobile biometrics vans.
The notice USCIS sends you about your biometrics appointment will tell you what to bring: typically a copy of the appointment notice and some kind of photo identification, such as a drivers' license or your passport. If you have only an expired passport, do your best to get a new one as soon as possible. If you are still waiting for a new one when your appointment is scheduled, bring a letter or receipt notice from your home country's embassy stating that your passport renewal is in progress.
In many cases, the notice will also tell you what you can't bring into the building. Don't expect to bring in a phone, camera, or food or drink.
You should also receive the latest COVID-19 related instructions. For example, in mid-2021, USCIS was advising people that they would have to answer health-screening questions before entering the facility, covering matters such as whether they'd traveled abroad recently and whether they'd been vaccinated. And everyone, whether vaccinated or not, must wear a mask or similar facial covering. (See the USCIS visitor policy for details on what types of masks are acceptable and so on.)
If you cannot make it at the scheduled time or on the scheduled day, you must ask to be rescheduled. Failure to do so can result in USCIS deciding your application has been abandoned, and canceling or denying it.
Although such requests formerly had to be done in writing, USCIS now accepts reschedule requests only by phone, at its Contact Center line. You will also be expected to establish good cause for rescheduling.
During normal (non-COVID) times, at the less-busy ASCs, the timing was somewhat flexible, so if you showed up an hour early, it would take you regardless of what your appointment time is. But that's less likely to happen while the pandemic is an ongoing concern, as the offices try to strictly control traffic flow. This includes forbidding entry more than 15 minutes before your appointment time.
It's never good to show up later than your scheduled time, but if an emergency causes you to be an hour late, try showing up and explain, asking to be processed right then anyway. If that doesn't work, immediately contact USCIS by phone and explain, then ask for a reschedule.
In scientific terms, "biometrics" means anatomical or physiological data by which a person can be uniquely identified. At your biometrics appointment, USCIS will most likely collect your fingerprints, take your photo, and have you sign your name for electronic capture.
The actual process takes about 20 minutes, though you might have to wait a while after you arrive. A number of people might have received the exact same appointment time as you did. As a general rule, everyone who was given the same appointment time will probably be called in on a first-come, first-served basis.
Once you arrive at the ASC, you might be given a number showing your place in line, or you might be asked to fill out and hand in a short form letting the ASC employees know you're there. They'll call your wait-list number or your name when it's your turn.
At the end of the biometrics appointment, you will be given a stamp on your appointment notice confirming that you attended. Keep this document safe, in case you are later asked for it or USCIS cannot find its record stating that you indeed came to the appointment.
Your fingerprints will be sent on for review by the U.S. Federal Bureau of Investigation (FBI), which will check them against records held by the police as well as by USCIS (which often takes the fingerprints of people caught crossing the border illegally).
The FBI will send a report to USCIS to confirm your identity and to show whether you have committed any crimes or immigration violations that might make you inadmissible, deportable, or otherwise ineligible for the benefit that you seek.
If you think you might have a criminal record but are not sure, consult a lawyer. The lawyer can help you get fingerprints done, and analyze the results. Some but not all crimes make you ineligible for immigration benefits. If you don't take care of this ahead of time, you won't discover until you get to your main USCIS interview what the FBI report says about you; and your application could be seriously sidetracked or delayed as a result.