Monthly · 30 shopping prompts · ChatGPT, Perplexity, Gemini
Which brands does AI recommend?
Every month we ask the same 30 shopping questions across 10 categories in ChatGPT, Perplexity and Gemini, with web search on, and count which brands each one names. Same prompts every month, so the trend is the story.
The first edition is being collected.
An edition publishes once at least 90% of the month's answers are in. Until then, here is exactly what it will measure. For your own brand, start a weekly Shelf Watch.
Method
How the Index is made
The prompts. 30 fixed shopping questions, three per category, written the way shoppers ask: a need and a constraint, never a brand. Each ends with “I'm shopping online in the United States.” They don't change month to month; a new prompt starts a new series.
The assistants. ChatGPT, Perplexity and Gemini through their APIs with web search on. API answers can differ from the consumer apps, which personalise; the models used are listed with each edition.
The count. A small model lists the brands each answer names, in order, from the answer text alone. A brand's share is the share of a category's answers that name it. Named first counts the answers that name it before any other brand. Retailers and review sites aren't counted as brands.
The limits. One run per prompt per month, and assistants vary run to run, so treat a single month as a sample. We keep every answer and its sources; ask us for the raw rows behind any number.
Panel
The 30 prompts
- Skincare
- What's the best moisturizer for dry, sensitive skin?
- Recommend a vitamin C serum that's worth the money.
- Which sunscreen brands are good for daily wear under makeup?
- Supplements
- What's a good magnesium supplement for sleep?
- Which protein powder brands are best for women?
- Recommend a high-quality fish oil supplement.
- Coffee
- What are the best coffee bean subscriptions?
- Recommend a whole-bean coffee brand for espresso at home.
- Which decaf coffee actually tastes good?
- Running shoes
- What are the best running shoes for flat feet?
- Recommend cushioned running shoes for marathon training.
- Which trail running shoes are best for beginners?
- Mattresses
- What's the best mattress for side sleepers with back pain?
- Recommend a mattress that sleeps cool.
- Which online mattress brands are the best value?
- Cookware
- What's the best non-toxic nonstick pan?
- Recommend a stainless steel cookware set that lasts.
- Which cast iron skillet brands are worth buying?
- Pet food
- What's the best dog food for a puppy with a sensitive stomach?
- Recommend a fresh dog food delivery service.
- Which cat food brands do vets recommend?
- Baby gear
- What's the best stroller for city living?
- Recommend a baby carrier that's comfortable for long walks.
- Which organic baby clothing brands are good quality?
- Apparel basics
- What are the best men's t-shirts that don't shrink?
- Recommend sustainable women's leggings for yoga.
- Which brands make the best merino wool socks?
- Home
- What are the best bed sheets for hot sleepers?
- Recommend a quiet air purifier for a bedroom.
- Which bath towel brands are the softest?