Placement Optimisation: What Meta Is Really Doing Explained

Quick Answer

Placement optimisation isn't about picking which placements to enable — it's about Meta deciding which placement an individual user sees your ad on, given that user's session, history, and your eAR per placement. Automatic Placements give Meta access to all eligible placements, then the ranker picks per-impression. Selecting fewer placements just constrains the ranker's options.

The Mechanism Explained

The eAR model has placement features baked in — your ad has a different eAR for Reels vs Feed vs Stories vs Marketplace, even with the same creative. Meta computes placement-specific eAR because user behaviour differs by surface (scroll-stop rate on Reels is 4-5x higher than Feed, but conversion rate is often lower).

When a user opens Instagram, the system iterates through eligible placements in their session: Stories first if they're in Stories, then Reels if they swipe over, then Feed if they exit Reels. At each surface, the ranker runs an auction. Your ad enters whichever auction it has the highest eAR for, given the user's state.

Three things matter:

Placement-specific eAR — Meta predicts a different probability for each placement
Cross-placement frequency — seeing your ad in Feed reduces eAR for the same ad in Stories
Creative aspect ratio handling — auto-cropped creative gets a small eAR penalty vs natively-formatted

When you opt out of placements, you remove options the ranker would have used to maximise your total value. The model can't compensate by bidding more aggressively on the placements you kept — it just delivers less.

The exception is when one placement has materially worse downstream conversion rate, which pulls your average CPA down. For some advertisers, removing Audience Network is genuinely beneficial because eAR is high (lots of accidental clicks) but post-click value is low. Verify with placement breakdown, not gut feel.

Practical Implication

Default to Automatic Placements. Audit placement breakdown after 7 days. Only opt out of a placement if its CPA is materially worse and it's cannibalising spend from better placements. Most placement opt-outs are based on superstition rather than data.

Real Numbers

Automatic Placements vs Feed-only: 18-30% lower CPA on average
Audience Network share of spend in Automatic Placements: ~5-8% typically
Reels placement eAR: 20-40% higher than Feed for video creatives

FAQs

Q: Should I opt out of Audience Network?
Only if your placement breakdown shows materially worse CPA there.

Q: Does opting out of a placement save money?
No — it usually just reduces delivery.

Q: Can I bid differently per placement?
No — placement-specific bidding was retired.

Q: Does creative format matter per placement?
Yes — native aspect ratios get an eAR bonus.

Q: What happens if I opt out of Reels?
You miss the highest-eAR placement for video right now.

Pix-Vu

Native-format creative gets an eAR bonus per placement. Pix-Vu generates multiple aspect ratios from a single product image so each placement gets the format it prefers — at https://pix-vu.com.