An ad description is one of the longer lines of text that appear under the headlines in a Google search ad. Where the headline catches attention, the description does the explaining: what you offer, why someone should believe you and what they should do next.
How ad descriptions work
In a responsive search ad, which is the standard text ad format, you supply between two and four descriptions, each up to 90 characters. Google then combines them with your headlines in different arrangements and learns which mixes suit which searches. In most cases up to two descriptions show at once, and on smaller screens or lower positions one may be shortened or dropped.
Because any description can appear next to any headline, each one needs to make sense alone. A description that starts “As mentioned above” or relies on a specific headline to be understood will read badly when paired with something else. You can force a description into position one or two with pinning, but every pin reduces the combinations Google can try.
Descriptions also feed into Google’s view of ad relevance and Ad Strength. Repeating the headlines word for word adds nothing; descriptions that add new information score better and usually read better too.
Why it matters
Ninety characters is roughly one good sentence, and it is often the deciding factor between two similar ads. Someone comparing three removal firms in Bristol sees three near-identical headlines. The description is where one of them mentions fixed quotes, insurance cover and weekend availability, and that detail wins the click.
Descriptions also filter. Stating “From £450 for a one-bedroom flat” or “Commercial clients only” puts off people who would never buy, which saves you the cost of their clicks. For a UK business paying several pounds per click, that filtering is worth real money.
Regulated sectors need extra care. Claims in descriptions are advertising claims under the CAP Code, and financial promotions must be fair, clear and not misleading under FCA rules, so a description promising “guaranteed approval” can cause problems well beyond Google’s own policies.
Common mistakes
- Writing only two descriptions when four are allowed, which gives Google less to test.
- Repeating the headline instead of adding new information.
- Vague claims such as “high quality service” that any competitor could make.
- Descriptions that depend on a particular headline to make sense.
- No call to action, so the reader knows what you sell but not what to do.
- Prices or offers that no longer match the landing page.
How to act on it
Write four distinct descriptions for each ad. A pattern that works well: one that expands the main benefit, one that gives proof (such as reviews or accreditations you really hold), one that removes a doubt (pricing, cover area, response time) and one with a clear call to action. Check each reads correctly beside every headline.
As an illustration, a dog groomer in Cardiff might write: “Full grooms for all breeds, with nail clipping and ear cleaning included in the price.” Then: “Rated by local owners on Google. See our reviews before you book.” Then: “Prices from £35, quoted by breed and coat, with no extras added on the day.” And finally: “Book online in two minutes and choose a weekday or Saturday slot.” Each line stands alone, and together they cover benefit, proof, price and action.
After a few weeks, look at the combinations report and the asset details to see which descriptions Google favours, and replace the weakest. Writing and testing ad copy is a large part of how I run Google search ads.