Two questions decide how much of the Shopping market you actually reach: how often your products appear at all, and who takes the placements when they do not. Impression share answers the first and Google tells you whether budget or rank cost you the rest; auction insights and price benchmarking answer the second.
You compete for these placements against a specific and largely knowable set of merchants, and Google exposes more about them than most advertisers use. Auction overlap names who you run into; price position usually explains who wins the click once you are both shown.
You need four data sources: auction insights from Google Ads (shows overlap rate and outranking share with competitor domains), competitive visibility from Merchant Center (shows your visibility vs competitors by category), price competitiveness data from Merchant Center (compares your prices to benchmark prices), and impression share data (shows what percentage of available impressions you're capturing). Combined, these give you a complete picture of your competitive position.
Review auction insights and competitive visibility trends weekly for major shifts. Do a deeper competitor audit monthly — checking competitor ads, pricing, and promotions. During peak seasons like Black Friday or back-to-school, increase to daily monitoring. The key is consistency: a monthly rhythm catches most competitive changes before they significantly impact your performance.
Impression share tells you what percentage of available impressions your ads received — it's about your coverage. Competitive visibility tells you which specific competitor domains appear alongside you and how their visibility compares to yours by product category. Think of impression share as your score, and competitive visibility as the scoreboard showing everyone's position.
Not individual competitor prices directly. Google provides aggregated benchmark prices through the Merchant Center price competitiveness report. For each of your products, you can see whether your price is above, at, or below the benchmark (an aggregate of what other merchants charge for the same or similar products). For specific competitor prices, you need to manually check their Shopping ads or use third-party price monitoring tools.