How the ad auction works

The ad auction is the mechanism that media platforms use to decide, in real-time, which ads to display and in what order. Since there are far more advertisers than available spaces, platforms need a fair and efficient way to distribute these spaces. The solution is to auction each display opportunity individually.

This auction happens automatically with every search and every feed scroll, without anyone noticing. In a single campaign, you participate in thousands of auctions per day.

Imagine the Google search results page for a commercial query. There are few ad spaces at the top and often dozens of companies vying to appear there. The auction solves this scarcity problem by deciding who deserves each position.

But platforms have a second interest: maintaining a good user experience. If they always showed the ad from whoever paid the most, even if it was irrelevant, people would stop clicking and trusting the ads. That's why the auction balances commercial interest (the bid) with the quality of the experience (the ad's relevance).

Three main factors determine the outcome:

• The bid: the maximum amount you are willing to pay for a click or action. It's the financial component.
• Ad quality and relevance: how useful and aligned the ad is with the person's intent. This includes the quality of the ad copy, the landing page, and the expected click-through rate.
• Context and formats: extensions, additional information, and the ad's expected impact are also taken into account.

The combination of these factors generates a score that defines the position of each ad.

In Google Ads, ad quality is summarized in a metric called Quality Score, a score from 1 to 10 based on three pillars: the ad's relevance to the keyword, the expected click-through rate, and the landing page experience.

The higher the Quality Score, the less you pay to appear in the same positions. A highly relevant ad can outperform a competitor who bids higher, simply by offering a better experience. Therefore, improving quality is one of the most efficient ways to reduce costs.

The final ad position is determined by Ad Rank, which combines your bid with the quality and expected impact of the ad. Simply put, it's as if the platform multiplies how much you pay by how good your ad is.

This explains a phenomenon that confuses many people: two advertisers with the same bid can occupy different positions, and an advertiser with a lower bid can appear above one with a higher bid. It all depends on the quality combined with the bid.

An important detail: in most auctions, you don't pay the value of your bid, but rather the minimum amount necessary to surpass the competitor immediately below you. This is called the second-price model. In practice, this means that setting a fair bid rarely makes you pay too much unnecessarily, because the effective value is calculated based on real competition.

Since quality weighs as much as the bid, you can gain positions by improving the ad, not just the budget. This involves writing more relevant ads aligned with search intent, directing people to a fast landing page consistent with the ad, and monitoring the click-through rate to understand what engages users. Investing in quality is what makes the same budget yield much more.