USCIS API Event Codes Decoder

USCIS processes all electronic cases (usually those starting with the IOE prefix) using the DHS Electronic Immigration System (ELIS). In the raw backend database, actions are tracked using shorthand database keys.

When you check the internal API status feed, you will see a list of actions labeled with codes such as eventCode: "IAF". These codes are defined by the federal government's National Information Exchange Model (NIEM).

Understanding Common Code Types

While there are nearly 500 individual codes in the NIEM database, most applicants will only encounter a few specific families of codes:

• Intake Codes (Start with I or A): These indicate receipt or filing, such as IAF (Internet Online ELIS Intake Filed) or AALB (Received at Lockbox).
• Biometrics & Checks (Start with C): Common examples are C14 (Biometrics Appointment Scheduled) or C19 (Biometrics Captured).
• Requests for Evidence (RFEs): Toggled by codes like C24 (Request for Evidence Sent) and C26 (Response to Request for Evidence Received).
• Decision Codes: Final actions, including C21 (Approved), DA (Approved), or EA (Denied).

Why does the API use these codes?

These codes keep database sizes small and allow different Department of Homeland Security (DHS) databases to communicate with each other instantly. Because different agencies (USCIS, Customs and Border Protection, and Immigration and Customs Enforcement) all use different software interfaces, they rely on standardized NIEM codes as a universal translator.

By checking your raw JSON timeline events, you can spot these codes the moment an officer updates your database record. Sometimes this happens hours or even days before the main visual website updates its generic user messages.