First, define it properly
A conversion is a specific action that moves someone closer to being a customer. Most tracking setups fail here, before any code is written, because the definition is vague.
Bad: "engagement". Good: "submitted the contact form", "completed checkout", "started a trial", "downloaded the guide".
Pick one primary conversion and at most two or three secondary ones. Sites that track fifteen conversions are sites where nobody looks at any of them.
The two mechanics
Destination-based. The conversion counts when someone reaches a specific page — a thank-you page, an order confirmation. Simple, robust, and it works without any JavaScript event wiring.
Event-based. The conversion counts when something happens on the page: a button click, a form submission, a video played to the end. Necessary for single-page applications and anything without a page change.
Prefer destination-based where you can. It is far harder to break, and a URL is easier to verify than an event that fires somewhere in your code.
Implementation, in the right order
1. Create the destination. Send successful actions to a dedicated URL that is only reachable after the action.
2. Make sure it is not reachable otherwise. A thank-you page indexed by search engines will inflate your conversions with organic traffic.
3. Register it in your analytics tool as the goal.
4. Test the whole path, including on mobile, and verify the number appears.
5. Only then add event tracking for the things a URL cannot express.
The mistakes that ruin the data
- Double counting. A page refresh on the thank-you page counts again; a payment provider redirecting back through the page counts again. Watch for conversion counts that exceed your actual orders.
- The indexed confirmation page. Add a noindex tag and check your own logs for direct hits.
- Firing the event before the action succeeds. Track the success callback, not the click.
- Tracking the click instead of the outcome. A click on "Submit" that failed validation is not a conversion.
- Losing the source. If your checkout runs on another domain, the referrer is lost unless you carry the campaign parameters across.
Reconcile with the truth
Your database knows exactly how many orders you took. Analytics only estimates. Compare them monthly.
If analytics reports fewer, the usual suspects are ad blockers, consent declines, and a tracking script that does not run on the confirmation page. If it reports more, you are double counting.
You are not trying to make them equal — you are trying to know the ratio, so you can reason with the analytics number and mentally correct it.
Attribution, briefly
Once conversions are counted, the next question is which source deserves the credit. Last-click attribution — the last source before conversion — is the default and it systematically overvalues brand search and direct traffic, because those tend to be the final step of a longer journey.
Rather than building a sophisticated model, add one field to your form: "How did you hear about us?" Self-reported attribution is imperfect, but it captures the podcast, the recommendation from a friend and the conference talk that no tracking system will ever see.