Anatomy of a responsive search ad (RSA)

In short: the only Search format today is the responsive search ad (RSA): up to 15 headlines and 4 descriptions that Google combines in every auction. You don't write an ad, you write pieces that have to work in any order. The "ad strength" Google shows is a diversity guide, not a quality grade nor an auction factor.

The classic text ad —two headlines, one description, always the same— no longer exists. Today the only Search format is the responsive search ad (RSA): you hand over pieces and Google assembles a different ad for each search. Understanding what those pieces are and how they combine is the first step to writing them well.

What are the parts of a responsive search ad?

A served ad does not show every piece: it shows one combination. On mobile, often just 2 headlines and 1 description. Design each piece so that it works on its own and in any order.

How does Google decide which headlines to show?

For each search, the system picks the headlines and descriptions it predicts will perform best with that query, that device and that history. Over time it learns which combinations perform and favours them. Consequences:

• You cannot control what each person will see (unless you pin, see below). Write pieces that neither contradict nor repeat each other.
• More variety of pieces = more possible combinations = more learning. But variety is not filler: 15 headlines saying the same thing add nothing.
• The ad improves on its own over time... if the pieces are good.

Should you pin headlines in an RSA?

You can pin a headline or description to a position (headline 1, 2 or 3; description 1 or 2): it will always appear there. Use it when something has to be seen (a legal requirement, the brand, a time-limited offer). Every pin reduces the combinations and, normally, performance; Google penalises it in «Ad strength». Rule of thumb: pin only what is essential, nothing more, and if you pin several headlines to the same position, Google will rotate between them.

What does ad strength mean?

When you create an RSA, Google shows an indicator (Poor / Average / Good / Excellent) with suggestions: more headlines, more variety, include keywords... It is a measure of the variety and coverage of the pieces, calculated before the ad has any data. It measures potential, not results.

What it is good for: an ad with «Poor» strength is almost always badly built (few pieces, all alike). What it is not good for: chasing «Excellent» at the cost of adding weak headlines or removing pins you need. Google reports that going from «Poor» to «Excellent» improves clicks and conversions on average, but the indicator is not a performance metric: performance is read in the asset report (lesson 5).

How many ads should an ad group have?

The official recommendation: at least two RSAs per group with Good/Excellent strength. In practice, two or three is the healthy range: one focused on the main benefit, another on a different angle (price, urgency, guarantee), perhaps a third as a test. More than three dilutes impressions and learning.

💡 Ninja trick: an RSA is never «finished». Each piece accumulates data about when it works and when it doesn't, and weak pieces drag the whole ad down. Continuous ad optimisation —replacing bad pieces with new ones, one by one, without resetting the ad— is the subject of the ebook «The eternal ad» and of our RSA Optimizer, which proposes new headlines with AI and swaps them in with your approval.

What you should remember

• An RSA is pieces (up to 15 headlines and 4 descriptions) that Google combines per search; 2-3 headlines and 1-2 descriptions get shown.
• Every piece must work on its own and in any order; real variety, not filler.
• Pin only what is essential.
• «Ad strength» measures variety potential, not performance.
• Two or three RSAs per ad group.