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Glossary
Glossary

Impression Share

Impression share is the percentage of eligible impressions your ad actually received. Lost impression share is split by reason — budget or rank — telling you whether to spend more or bid more.

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Impression share (IS) is your ad's impressions divided by the impressions it was eligible to receive given your targeting:

Impression Share = Impressions Received / Impressions Eligible

A 100% IS means you appeared every time you could have. A 40% IS means six out of ten eligible auctions did not show your ad.

The two reasons impressions are lost

Amazon's reporting splits lost IS into two diagnostic buckets, and they map to two completely different fixes:

Lost IS reasonWhat it meansFix
Lost IS (budget)Campaign ran out of daily budgetRaise the budget or pace it
Lost IS (rank)Bid was too low to clear the auctionRaise the bid or improve the relevance score

Confusing these is the most common impression-share error. Adding budget when you are losing to rank does nothing. Raising bids when you are losing to budget compounds the problem.

Top-of-Search Impression Share

A subset metric: of the impressions that were in Top of Search, what percentage were yours? This is the metric to optimise for branded defence and for keywords where your CVR at Top of Search is more than 2× the rest-of-search CVR.

The lever is the Top of Search placement modifier — adding 50% or 100% to bids when the auction is at the top.

Healthy targets

Use caseTarget IS
Generic high-volume keywords25–40%
Long-tail converters60–80%
Branded defence85–100%
Top-of-Search IS on branded70–90%

100% IS on broad targeting is almost always a budget waste. 100% IS on branded is non-negotiable.

Common mistakes

  • Treating impression share as a goal in itself. Share of irrelevant impressions is share of waste.
  • Increasing budget on a Lost-IS-rank problem. The campaign was never eligible — extra budget sits idle.
  • Ignoring branded IS. A competitor running ads on your brand term with higher IS than yours is a public-facing problem.

Related terms

Impression
An impression is one render of an ad on a shopper's screen. It is the top-of-funnel volume metric — every click and every sale starts as an impression.
Daily Budget (Amazon Advertising)
The daily budget is the maximum amount Amazon will spend on a campaign in a single day before pausing it until the next day. Budget allocation by campaign role — not equal distribution — determines whether an account scales profitably.
Bid (CPC Bid)
A bid is the maximum cost-per-click an advertiser submits for a keyword or product target in an Amazon Advertising auction. It is the ceiling — the realized price paid per click is the CPC.
Top of Search (TOS)
Top of Search is the placement bucket covering the first row of search results on the Amazon SERP — typically the highest-CTR, highest-CVR, and highest-CPC placement available. The Top of Search bid modifier is the single most impactful bid lever in Amazon Advertising.
Placement Bid Modifier
Placement bid modifiers are percentage multipliers (0–900%) that increase a base bid for specific placements — Top of Search, Product Pages, or Rest of Search — letting advertisers buy premium real estate without raising the campaign-wide bid.

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