Headline pinning is an RSA control that locks a specific headline (or description) to a fixed position — 1, 2, or 3 — so it appears in every ad impression at that slot. Pinning guarantees visibility for required messaging but reduces the combinations Google can test, usually at a performance cost.
By default, Google assembles RSA combinations freely from your asset pool. Pinning overrides this: a headline pinned to position 1 shows in slot 1 of every impression, and any unpinned headline can no longer appear there. Pin two headlines to the same position and Google rotates between just those two for that slot — a common technique to retain some testing within a constraint.
The math explains the cost. Fifteen free headlines give the system thousands of viable combinations; pin one headline to position 1 and you have eliminated every combination that doesn't start with it. Google's systems optimize by exploring; pins shrink the exploration space, which is why pinned RSAs cap out at lower Ad Strength and, in most published agency tests, convert somewhat worse than unpinned equivalents.
Legitimate pinning cases are real, though: regulated industries where a disclaimer must always show (finance, pharma, legal); brand governance that mandates the brand name in position 1; offers that lose coherence if separated ("50% Off Ends Friday" pinned with its terms description). The discipline is pinning the minimum — one position, ideally with 2–3 alternates pinned to that same position so rotation survives.
Before pinning for preference rather than compliance, try the alternative: write the must-have message into several headline variants so it likely appears anyway, or pin to position 2 instead of 1 (position 1 attracts the most algorithmic attention; a position-2 pin constrains less valuable real estate). And after pinning, watch the per-asset impressions report — pins reshape which assets ever get shown.
A mortgage lender must always show "Licensed Lender — NMLS #12345". Instead of one pin, they pin three compliant variants to position 3 — keeping the disclaimer guaranteed while positions 1–2 stay fully free for Google to optimize keyword and benefit headlines.
Yes — pinning restricts combinations, and Ad Strength penalizes restricted variety. A heavily pinned RSA often caps at Good or Average. That's acceptable when compliance requires it; the rating is guidance, not an auction factor.
Yes, and you should when pinning at all: pinning 2–3 headlines to the same position makes Google rotate among them for that slot, preserving some testing inside your constraint.