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The three steps Meta runs on every ad, in plain language: how GEM and Andromeda read, shortlist, and rank your creative, and the moves that help you win.
The video above walks through the whole system in nine minutes. This page is the study-guide version: the three steps Meta runs on every ad, what each step reads, and the practical move that follows from each one.
How does the Meta ads algorithm work? Meta's ad system runs three steps. A foundation model called GEM reads and summarises every ad, the Andromeda retrieval engine narrows tens of millions of candidates to a few thousand for each person, then GEM ranks that shortlist in detail before the auction picks the final winner.
Before your ad is shown to anyone, Meta's generative ads model (GEM) reads it in full: the copy, the visuals, the audio, the video. It works out what the ad is and who it suits, then stores a summary. There is no targeting form for this part. The creative itself is the input.
The practical consequence: everything in the ad is a signal you are sending, whether you meant to send it or not. A cluttered visual, a generic hook, or a mismatched voiceover all shape who the system thinks the ad is for.
Meta's Andromeda retrieval engine scans those summaries every time someone opens the app and cuts tens of millions of ads down to a few thousand candidates for that person.
Here is the part most accounts miss: Andromeda groups ads it reads as functionally the same, so twenty near-identical variations compete as one. We cover the mechanics in Meta's hidden Entity ID problem. If your ads are all variations of one idea, you enter this stage with one ticket, not twenty.
GEM reads the shortlist closely and ranks each candidate on six dimensions, a framework known as POSTER:
The survivors go to Meta's ad auction, where the winner is the combination of your bid, how likely the person is to act, and how likely they are to genuinely enjoy the ad. A strong creative match regularly beats a higher bid.
Each step favours accounts whose ads are genuinely different from each other. Different personas, different emotions, and different formats give Andromeda more distinct candidates to retrieve and GEM more profiles to match. Small tweaks to one concept do not create that range. This is why creative diversity is the working lever, and we keep a full guide on how to measure and improve creative diversity.
Meta never shows you this scorecard. Ads Manager will not tell you that one ad was read as humour for busy parents and another as nostalgia for athletes. Wilow rebuilds the picture from the outside: AI Creative Tagging labels every ad in your account the way the system reads it, and the Creative Leaderboard ranks what is actually winning. Start free, no credit card required, and see the profile the algorithm has built for your account.
Want the full theory? Read the complete deep-dive on The Keyword: how the Meta algorithm decides which ads you see.
Meta’s ad system runs three steps on every ad. First, the GEM foundation model reads and summarises the creative — visuals, audio, copy, everything. Second, the Andromeda retrieval engine scans those summaries and narrows tens of millions of ads to a few thousand candidates for each person. Third, GEM ranks that shortlist in detail across six dimensions (persona, offer, format, creative type, emotion, and audience readiness), then the auction picks the winner. The full walkthrough is in the video above.
Andromeda is Meta’s retrieval engine, deployed to replace the old interest-based targeting system. Instead of advertisers picking who sees their ad, Andromeda reads the creative itself and matches it to people. This means the creative is now the targeting input — what you show determines who sees it. The practical consequence: creative diversity matters more than audience settings. Accounts that run genuinely different ads (different formats, emotions, personas) give Andromeda more distinct candidates to retrieve. Accounts that run variations of one idea enter the system with one ticket, not twenty.
Creative fatigue is the most common cause. Meta’s algorithm shows your ad to people it predicts will respond, but after 2-4 showings to the same person, engagement drops sharply. The fix is not more budget — it is more creative diversity. The brands that scale on Meta run ads that are genuinely different from each other (different hooks, formats, emotions), not small variations of one concept. When each ad reaches a different audience, the system has more room to deliver. The Creative Diversity guide linked above covers how to measure and improve this.
Not universally, but video tends to earn more delivery because it generates more engagement signals — longer view times, more saves, more shares. However, a strong image ad that generates high engagement will beat a weak video ad. The format is not the deciding factor. The deciding factor is whether the ad matches what a real person wants to see in their feed right now. Video is a better bet for most brands because it gives you more seconds to earn that match, but a compelling static image with a sharp hook can outperform a mediocre video every time.
Creative diversity is the spread of genuinely different ads in your account — different hooks, formats, emotions, creative types (UGC, testimonial, demo, founder story), and personas. Meta’s Andromeda engine groups ads it reads as similar, so running twenty variations of the same concept counts as one ad in the retrieval stage. The brands that scale on Meta run ads that are meaningfully different from each other, not just different in small details. Wilow measures creative diversity automatically across every ad in your account — the Creative Leaderboard shows you the spread, and the Outliers chart flags the few ads doing all the work. Start free, no credit card required.