Search Advertising Fundamentals
How the search auction works
Every eligible query triggers an auction. Eligibility depends on keywords and match types, targeting settings, bids, budgets, and ad formats. The auction determines whether an ad shows, its position, and the actual CPC paid.
Ad Rank is the deciding score, and it is not a number you set. It combines your bid, ad quality signals (expected CTR, ad relevance, landing page experience), the expected impact of assets/formats, and auction-time context such as device, location, time, and the query itself. Quality Score (1-10) is a keyword-level diagnostic that summarizes expected CTR, ad relevance, and landing page experience - it is not the literal multiplier used in the auction.
Common traps
- Assuming the highest bid always wins. A high bid with weak quality can lose to a lower bid with strong quality.
- Treating Quality Score as a direct CPC formula. Actual CPC depends on the Ad Rank threshold of the ad below you.
- Confusing keywords (what you bid on) with search terms (what the user typed).
- Assuming Search Partners behave exactly like Google Search, or that every keyword earns impressions.
Rule of thumb: if impression share is low and Quality Score is weak, fix relevance or the landing page first; raising bids often just buys the same position more expensively.
Worked example: Ad A bids $2.00 with Quality Score 10; Ad B bids $4.00 with Quality Score 4. Using the simplified rank estimate bid × quality, A scores 20 and B scores 16. A wins, and pays roughly the amount needed to beat B - about $1.61 - not its full $2.00 bid.