How Andromeda and GEM work together

When Meta launched advertising nearly two decades ago, performance was driven by manual inputs – targeting rules, account structure, and incremental optimization.

Success depended on carefully defined audiences, granular budget control, and frequent testing.

That operating model eroded over time as privacy changes and signal loss made deterministic targeting less reliable.

Over the last two years, Meta responded by fundamentally rebuilding its advertising platform around AI.

That rebuild began with Andromeda, a personalized ads retrieval engine, and expanded into Meta’s Generative Ads Recommendation Model (GEM).

Together, these systems now determine how ads are selected, ranked, and delivered across Meta’s ecosystem.

Meta Ads is no longer an open, manual optimization environment. Performance now depends on understanding how the system evaluates inputs and learns over time.

This article breaks down how Andromeda and GEM work, how they changed ad delivery, and what it takes to align strategy with Meta’s AI-first advertising system in 2026.

Andromeda is Meta’s AI-driven ads retrieval system that decides which ads are eligible to be shown to a user. 

Instead of starting with advertiser-defined audiences, it works in reverse, by first evaluating historical engagement, ad copy, creative, and format. 

This helps Andromeda predict which users are most likely to engage with the ad and contribute to your campaign optimization goals.

This AI system began rolling out in late 2024. In 2025, Andromeda became a core component of Meta’s updated infrastructure.

Advertisers saw changes firsthand as:

• Broad targeting began to outperform previous top-performing interest stacks.
• Simplified account structures started to win.
• Creative fatigue accelerated. 

These were blatant signals that ad retrieval had changed.

What Andromeda changed

With the rollout of Andromeda, Meta shifted away from audience-first advertising to creative-first matching. 

Targeting became less deterministic as interests and lookalikes no longer performed as strongly as they once did.

Instead, creatives became the primary signal as the system evaluated creative elements like visuals, themes, hooks, and language to determine relevance.

AI drives better performance when it has a larger opportunity pool to draw from. 

Broader campaigns with more creative inputs give the system more options to match ads to users to achieve campaign goals.

GEM is Meta’s large-scale generative AI system that acts as the ad platform’s central intelligence. 

It identifies patterns across organic interactions and ad sequences, formats, and messaging, synthesizing engagement, behavioral, and conversion data.

Most importantly, GEM feeds predictions into Andromeda. These insights help predict what works best, for whom, and when, at scale, while continuously learning.

GEM began rolling out in mid-2025, with…