Most say they do. We open yours in a real browser, wait for the service worker, cut the network, and read what is still there. You get the manifest, the cache contents, and the two or three things Android will do differently than you expect.
id is pinned, so a future change to start_url does not orphan everyone who already installed.No score out of 100. A score averages things we did not measure, and this directory only publishes what it observed. You get the observations.
The measurement drives a real browser — load, wait, disconnect, re-read. It runs in batches and the report arrives by email, usually within a day. We would rather be slow and right than instant and guessing from your HTML.
Compare the result with the current evidence attached to the 776 apps in the directory. 284 entries currently carry offline evidence; run the check again before relying on it.
One email a month, only when there is something worth sending. Last one: most of the PWAs we measured ship no maskable icon, so Android puts their square logo in a white circle.