Definition: Search Impression Share (Search IS) is a Google Ads metric that measures the percentage of total impressions a campaign or ad group actually received, out of the total number of impressions it was eligible for based on its targeting, keywords, and auction eligibility. For example, a Search IS of 60% means the campaign showed in 60% of the auctions it could have entered, missing 40% of potential impressions. Search IS is a key indicator of how fully a campaign is capturing available search demand.
Why It Matters: Low Search Impression Share reveals untapped opportunity — your ads are eligible to show but are not appearing, either because of insufficient budget (Budget Lost IS) or bids and Quality Scores that are too low to win auctions (Rank Lost IS). For campaigns targeting high-value keywords with clear commercial intent, a low IS means competitors are capturing demand that could be yours. Conversely, maintaining near-100% IS on core branded keywords is a standard defensive strategy to ensure no competitor is intercepting your brand traffic. IS data informs decisions about budget increases, bid adjustments, Quality Score improvements, and keyword expansion.
How It Works: Search IS is visible in Google Ads at the campaign, ad group, and keyword level by adding the Impression Share, Search Lost IS (budget), and Search Lost IS (rank) columns to campaign reports. Budget Lost IS shows the proportion of missed impressions due to insufficient daily budget running out. Rank Lost IS shows the proportion missed because Ad Rank was too low — addressable by improving Quality Score (more relevant ads and landing pages) or increasing bids. IS is calculated daily and averaged over the selected date range. Note that IS is only available for Search and Shopping campaigns; Display campaigns use a separate Display Impression Share metric.
Related: Google Ads, Impression Share, Quality Score, Ad Rank, Bid Strategy