Why is Meta spending my whole budget on one ad?

This is Meta working as designed, not a bug. Inside an ad set the algorithm concentrates budget on the ad it predicts will win, often within the first hours, so the other ads get little or nothing. If you need a fair test, isolate each creative instead of fighting the allocation.

What this means

This is Meta working as designed, not a bug.

Quick steps

Confirm it is allocation, not stalled delivery: the ad set is spending and one ad simply holds most of the budget and results.
Decide if equal spend even matters: if the chosen ad is profitable, let it run. Only force even testing when you need a clean read on each creative.
To test creatives fairly, give each one its own ad set, or a small dedicated testing budget, rather than many ads competing inside one ad set.

Run the diagnostic

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