QR Code Checker

Look at what is inside it. A static code contains the destination itself: the website address, the WiFi password, the contact card. A dynamic code contains a short link on someone else's server, which forwards to the destination. Upload the code above and the checker shows which one you have and every step the link takes.

No. A static code is just data printed as a pattern, and no service is involved when it is scanned, so there is nothing to switch off. It stops working only if the destination itself disappears, for example a website that is taken down.

Almost always because it was dynamic and the service behind the short link stopped forwarding it: a free trial ended, a subscription lapsed, or an account was closed. The pattern on the page is fine; the server it points at changed its answer. The checker shows where the chain now ends.

Only through the provider whose short link is printed in it, usually by reactivating the account. Nobody else can change where that link goes. If that is not an option, the fix is a new code, and the lesson is to choose a provider that does not expire codes.

It follows the link the way a phone does and records each response. A clean redirect answers with a forwarding instruction and no page at all, so there is nothing to put an ad on. If a page is served on the way to the destination, that page is where ads or a countdown can appear, and the checker flags it.