Conversion arrived again under its identifier

What was observed

A conversion reported by the browser arrived in a session where no declared step was seen earlier that day, under an identifier that had already arrived from the browser in an earlier event. TraceLog counts each conversion once by its identifier, so the second event is not a second conversion.

It usually means a page sends the conversion again when the buyer comes back to it: the order confirmation opened again from an email, the cart, or the return from a payment provider.

It is raised on sites that send their own conversions, with the snippet or the npm package. On Shopify, WooCommerce and PrestaShop, TraceLog's app, plugin or module sends the purchase, so there is nothing to change and the row is not raised.

In the application the row names the day, how many events the browser sent that day, and how many of them arrived this way. It never names the identifier.

What to check

1. Check that the identifier is each order's own number, different for every order. A fixed value sent in its place, such as undefined, makes different orders arrive under one identifier, and they read as sent again. Once it repeats across visits it is a duplicate conversion identifier.
2. Find where the conversion is sent, and check that it is sent when the conversion happens, such as when the order is placed, and not each time a page loads.
3. Open the confirmation page again from the link in the confirmation email, and go back to the cart after paying: neither should send the conversion.
4. If the page cannot tell a first visit from a return, send the conversion from the step that places the order, not from a page that can be opened again.

Effect on verification

It warns and never blocks. An install can still show Conversion path verified with this condition present, and the condition stays visible on the Path page.