What Google says
In Google's own words: “Responsive search ads let you create an ad that adapts to show more relevant messages to your customers.” (Google help center)
How RSAs work
You provide the raw material, headlines and descriptions, and Google mixes them per auction to fit the query and the user, learning which combinations perform. Ad Strength gives feedback on how much variety and relevance you have supplied, though it is guidance, not a ranking factor.
Getting the most from them
Give genuinely distinct headlines rather than near-duplicates, include your main keyword in a few, and pin sparingly, since over-pinning removes the testing that makes RSAs work. Strong, varied assets feed the same Quality Score signals that lower your cost per click.
A worked example
Say you write the full 15 headlines and 4 descriptions. An ad shows up to 3 headlines and 2 descriptions, so Google can order them 15 x 14 x 13 = 2,730 ways for headlines and 4 x 3 = 12 ways for descriptions, or 32,760 possible ads. Pin one headline to position 1 and the headline orderings drop to 14 x 13 = 182, or 2,184 ads, which is why we pin only what must always show.
Common questions
How many headlines does an RSA need?
You can supply up to 15 headlines and 4 descriptions. Providing a full, varied set gives Google more combinations to test and usually improves performance.
Should I pin headlines in an RSA?
Sparingly. Pinning guarantees a message appears in a position but reduces the combinations Google can test. Pin only what must always show, such as legal or brand requirements.
What are the character limits for a responsive search ad?
Headlines allow up to 30 characters, descriptions up to 90 characters each, and the 2 display path fields up to 15 characters each. Characters in double-width languages like Korean, Japanese, or Chinese count as 2.
What is the minimum number of headlines and descriptions?
You need at least 3 headlines and 2 descriptions, and can add up to 15 headlines and 4 descriptions. Google recommends at least 2 responsive search ads per ad group with Good or Excellent Ad Strength.
Did responsive search ads replace call-only ads?
Yes. Google is replacing call ads (call-only ads) with responsive search ads plus call assets: creating new call-only ads was removed in February 2026, and existing ones stop receiving impressions in February 2027.