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A conversion is attributed when we join it to an earlier visit that carried campaign context. Four things must hold, and only one of them is usually missing.

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The four inputs

Every join needs a click ID or a utm_source, so a visit with neither is never attributable, whatever else is correct.

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1. The landing URL

We capture these fifteen click IDs. We also capture utm_source, utm_medium, utm_campaign, utm_term, and utm_content. Confirm what the browser captured with window.datalyr.getAttribution().

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2. Identity on the conversion

A conversion with no visitor_id and no anonymous_id is unattributable, so there’s nothing to look up.
Do not send your application user ID as visitor_id from a server. It never matches a browser identifier, so those conversions can never join a web session.

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3. The lookback window

Our own lookup covers 90 days. Each ad platform gets a shorter window when a conversion is delivered. A Meta purchase 10 days after the click resolves to no fbclid, because the window closed. Attribution joins on clicks only, so a view-through conversion is never credited.

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4. The journey breaks

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Verify with one clean test

  1. Open a private window.
  2. Land on your page with ?utm_source=docs_test&utm_campaign=attr_check.
  3. Confirm the pageview in Events carries both values.
  4. Complete a purchase in the same window.
  5. Open Users and confirm the attribution block holds docs_test.
A successful delivery to Meta reports only that the platform accepted the request, so it never proves attribution. See Conversion not delivered.