Search and Marketing Engineering

Match the Landing Page to the Ad

A visitor who clicks an ad with a specific offer should land on a page showing that offer. I built a script that read the VIN from the URL and updated price, discount, and disclaimer.

By Joshua Hayes October 14, 2026
JavaScript Landing Pages Google Ads Automotive APIs

An ad promises something. If the page that opens shows something different, people leave, and in regulated advertising the mismatch can create legal trouble too.

At World Car Auto Group, some ads carried custom discount and finance rates. The vehicle page had to show the same offer.

The problem

An ad could state a specific discount and finance terms. A visitor arriving from that ad needed to see the same numbers on the page, with the legal disclaimer that came with the offer.

What I built

  1. Each ad click sent the visitor to the vehicle detail page with ?vin= and the vehicle’s VIN in the URL.
  2. A JavaScript snippet on that page read the VIN parameter.
  3. It called the same API that built the ad feed, so it got the same offer data.
  4. It updated the price and discount shown on the page.
  5. It added the legal disclaimer to the top of the page.

Why the same API

Using the API behind the ad feed meant the ad and the page read one source. They could not drift apart, because there was no second copy of the offer to maintain.

The pipeline behind it is described in the inventory ad feed pipeline case study.

Design points

  • URL parameters carry the context. The page does not need to guess which ad was clicked.
  • The disclaimer is part of the change. Matching the price without matching the legal language solves only half the problem.

Legal requirements vary, so the exact disclaimer text should come from the business and its counsel.

What happened to it

The script was retired shortly after COVID, when the business stopped offering those discounts. That was a business decision, not a technical one.

I have no results data for it, so I do not claim any.

Takeaway

Message match is a data problem as much as a design problem. When the ad and the page read from the same source, consistency comes from the system and not from people remembering to update two places.

If you need ads and pages to stay in sync, see the data pipelines and automation service.