How to read every number on this site
USCIS publishes, for each form and office, the range in which roughly 80% of recently completed cases finished. A case that says 13.5 to 28 months is not promising an answer in month 28 — it is telling you that 8 of 10 cases like yours were done by then. Faster cases fall below the range, slower ones above it. Two extra numbers make the picture honest: the case inquiry date (the oldest receipt date USCIS says it is still working on — older than that, and asking "where is my case" becomes reasonable), and the previous release, which turns a static table into a trend.
That history matters more than it sounds: USCIS overwrites its published figures in place, every month, with no archive. This site keeps the recent releases side by side so you can see whether your office is speeding up or slowing down — the one question the official tool cannot answer.
What this site is not
It is not a case status checker: only USCIS can look up your actual case, free, with your receipt number on the official site. It is not legal advice, and it is not affiliated with USCIS or any government agency — see the full disclaimer. What it is: the clearest possible read of the government's own waiting-room numbers, for the six forms that cover most immigrant journeys.