Impression share is the percentage of eligible impressions your ads actually received — how much of the available demand you captured versus left on the table.
Definition
Impression share = impressions received ÷ impressions you were eligible for. Platforms also report what you lost and why: lost to budget (you ran out of money) versus lost to rank (your bid or quality wasn't competitive). Those two loss reasons have opposite fixes — more budget versus better ads or bids.
Why it matters
Impression share turns 'can we scale this?' from a guess into arithmetic. High impression share means growth must come from new campaigns, audiences, or channels; low share lost to budget means the fastest growth lever is simply funding what already works.
In agentic execution
Adlyse's agents use impression share and loss reasons in scaling decisions — proposing budget increases where demand is being left behind and structural changes where rank is the constraint, all human-approved before execution.
Related terms
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