Amazon's 2025 Algorithm Shift Is Quietly Undermining Exact Match Strategies

Something changed in Amazon's ad algorithm starting around June 2025, and most supplement brands haven't fully adjusted for it. Auto campaign impression share jumped approximately 7 percentage points and now accounts for over 40% of total impressions in many accounts. Simultaneously, exact match impression share fell by 10–12% in some portfolios. Broad match overtook exact match in total impression share across several competitive supplement accounts. The platform is shifting from keyword-string matching to semantic intent routing — and brands still running exact-match-heavy structures are leaving money on the table.

What Actually Changed

Amazon has been moving toward semantic matching for several years, but the pace of the shift accelerated meaningfully in Q2 2025. The specific changes documented by practitioners:

• Auto campaign Loose Match and Substitutes subtypes are gaining impression share, while Close Match is declining. This means Amazon is making more interpretive decisions about what your ad is relevant for.
• Within auto campaigns, Amazon is increasingly serving impressions for search terms that don't contain any of your targeted keywords but are semantically related to your product.
• Broad match campaigns are receiving impressions for a wider vocabulary than before, including synonym expansions and conceptual matches.
• Exact match campaigns, while still delivering the most controlled traffic, are no longer enough to capture the full breadth of relevant search volume.

This mirrors what happened on Google Ads years ago when 'close variants' began expanding exact match to include semantically similar queries. The brands that adapted their structure early won. The ones that held onto rigid exact-match-only approaches saw their impression share erode.

Why This Particularly Affects Supplement Brands

Supplement PPC has traditionally relied heavily on exact match for several important reasons: compliance control (you know exactly which terms you're bidding on), efficiency management (exact match CPCs are more predictable), and brand safety (you're not suddenly appearing next to disease-claim adjacent searches).

The algorithm shift creates a dilemma: if you stay exact-match-heavy, you lose impression share to the semantic expansion Amazon is doing through auto and broad. But if you open up auto and broad without strong negative keyword discipline, you're exposed to two risks specific to supplements:

1. 1Compliance risk: Amazon routing your supplement ad to a disease-name search term, which triggers policy enforcement.
2. 2Efficiency risk: Supplement CPCs are $2.50–$7.00+. Wasted impressions and clicks in this category cost significantly more than in most others.

The Structural Response: Harvest More Aggressively, Negate More Systematically

The algorithm shift doesn't mean abandoning structure — it means updating the structure to work with the new environment rather than against it.

1. Keep auto campaigns running — but treat them as data engines, not revenue engines

Auto campaigns with the new Loose Match/Substitutes expansion are surfacing vocabulary you wouldn't have found through manual keyword research. Let them run at a controlled spend level, pull the search term report weekly, and harvest converting terms into manual campaigns. The goal is to capture Amazon's semantic intelligence without paying auto-campaign CPCs for your best keywords.

2. Build negative keyword walls before expanding match types

Before expanding into broad match, build a comprehensive negative keyword list based on your search term report history. For supplement brands, this means specifically flagging: disease name patterns, competitor brand terms where you have low conversion rates, and adjacent category terms (food, pet supplements, beauty) that bleed into supplement searches.

High-performing supplement accounts typically have 3–5x more negative keywords than positive keywords. This is not an exaggeration — it's the actual ratio required to manage broad and auto match types responsibly in a high-CPC, compliance-sensitive category.

3. Exact match still wins for your highest-value terms — protect them

Exact match isn't dead. It's still the right tool for your top 20–30 highest-converting keywords. Bid aggressively on exact match for terms where you have proven conversion data, use placement adjustments to secure top-of-search position, and let broad and auto cover discovery. The mistake is running exact match exclusively — or abandoning it entirely.

The New Campaign Structure for 2025–2026

Based on the current algorithm environment, a supplement brand's campaign structure should look like this:

• Auto campaign (Loose Match + Substitutes enabled): Data discovery, weekly harvest cadence, strict negative keyword management
• Broad match campaign: Vocabulary expansion, moderated bids, aggressive negation of waste patterns surfaced from search term reports
• Phrase match campaign: Middle tier — captures intent-qualified searches, less aggressive negation required than broad
• Exact match campaign: Top 20–30 proven keywords, highest bids, top-of-search placement adjustments, brand defense terms
• Sponsored Brands: Brand keyword protection — essential given competitors are actively bidding on supplement brand terms