What happens when someone searches
When a person types a query or loads a page with ad space, the advertising platform has a very short time to decide which ads, if any, to show and in what order. It does this with an automated auction that runs again for every search or page view. No two auctions are exactly the same, because the query, the person, the competing advertisers and the time of day can all differ.
This article describes the general idea. The exact rules and formulas are set by each platform, are not fully public and change over time, so treat the explanation as a mental model and check the platform’s current documentation for specifics.
Who gets into the auction
Not every advertiser takes part in every auction. An ad is usually eligible only if:
- the search or placement matches your targeting, such as a keyword, audience, location or language;
- your campaign is active and has budget remaining that day;
- your ad meets the platform’s policies.
Choices like match types affect which searches you enter. If you target too loosely you enter auctions you do not want; if you target too tightly you miss searches you do.
Bids
A bid is the most you are willing to pay for a click. Many platforms also let you ask for automated bidding aimed at a goal such as conversions, in which case the system adjusts the effective bid per auction itself.
A bid is a ceiling, not a price. In common auction designs, what you actually pay for a click is often lower than your maximum, because it is set in relation to what the competition requires to win. That is why the cost per click you see in reports is an average of many different auction outcomes.
Relevance and expected performance
If the highest bid always won, advertisers with the deepest pockets would take every position, and users would see irrelevant ads. Platforms generally avoid that by also scoring how useful an ad is likely to be to the person searching.
While the details differ, such scores typically draw on ideas like:
- how likely the ad is to be clicked, based on past performance;
- how closely the ad matches the search;
- how good the experience on the landing page appears to be.
Some platforms present a simplified version of this as a rating, such as quality score. These are diagnostic indicators that help you spot weak areas, not the full auction calculation.
Putting it together: ad position
In broad terms, an ad’s standing in the auction results from combining the bid with these relevance signals. A simple illustration, using made-up numbers and not any platform’s real formula:
- Advertiser A bids 4 and has a lower relevance rating of 5.
- Advertiser B bids 3 and has a relevance rating of 8.
If standing were bid multiplied by rating, A would score 4 x 5 = 20 and B would score 3 x 8 = 24. B would rank higher despite the lower bid. Real systems are more complex and also account for things like ad assets and the expected effect of extensions, but the principle holds: relevance can offset a smaller bid.
This also means a relevant ad can sometimes win a good position while paying less per click than a less relevant competitor. It is a reason to write tight search ad copy and send people to a landing page that fits the search, not just to raise bids.
Why you might not appear
Common reasons an ad does not show, even though it is active:
- The daily budget has run out for the day.
- The ad or keyword is not considered relevant enough to the query.
- The bid is too low to win against competitors.
- The ad is waiting for review or was disapproved.
- Targeting settings, such as location or schedule, exclude the search.
Position is also not the same as success. The top spot often costs more and attracts more casual clicks. A lower position at a lower cost per acquisition can be the better deal, which is why you should judge results by cost per result rather than position alone.
What you can and cannot control
You can control your targeting, bids, budget, ad wording and landing page. You cannot control competitors’ bids, how many people search, or the platform’s internal scoring. Because competitors enter and leave, costs can shift from week to week without any change on your side.
Be wary of anyone who claims to know a secret trick for beating the auction. The rules are the platform’s, they change, and outcomes are uncertain. The dependable approach is to be relevant, measure what you pay for each result, and read the platform’s own help pages for the current details.