An ad occupies borrowed space. A homepage or a product page waits for the reader to arrive and then has the run of the page to make its case, but an ad gets a few words, a fixed slot, and a reader who has not agreed to look at it. That difference decides most of what follows: how you open, what you promise, and how much you can afford to say before the reader moves on.
Ad copy is copywriting with the safety net removed
On most pages, a flat sentence costs you some momentum and the reader might forgive it and read on. On an ad, it costs money: you pay for the impression whether or not anyone clicks, and you pay for the click whether or not it buys anything. A vague headline does not simply underperform, it sits there turning budget into nothing while a sharper version, run alongside it, would have earned the click instead. Every word in an ad is being tested against an alternative, even when nobody has formally set up the test.
Build the ad around a hook, a benefit and one instruction
Search, social and display ads all work on the same three-part structure, even though the space they give you is different. The hook connects to what the reader was already thinking, whether that is the phrase they typed into Google or the feed they were scrolling past. The benefit tells them what they get if they act. The CTA (call to action, the instruction that tells the reader what happens next if they click) names that action plainly.
Take a fictional example: an invoicing app aimed at UK sole traders. A weak version of the ad reads "Business Software Solutions | Try Today". It says nothing about who it is for, gives no reason to prefer it over the ten other results on the page, and asks the reader to "try" something without saying what. A working version reads "Invoicing Software for Sole Traders" with the description "Send invoices from your phone. No monthly fee. Start a free account." The headline names the exact reader, the description gives a concrete benefit and removes a common objection, and the CTA says what happens if they click.
Match the hook to what the reader typed or scrolled past
A search ad is answering a question the reader has already asked, so the strongest hook usually repeats their own words back to them: the trade, the problem, or the outcome they searched for. A social ad is interrupting someone who was not looking for you at all, so the hook has to work harder in less friendly territory: it needs to name a situation the reader recognises within the first few words, because that is the only part of the ad most people will read before deciding whether to keep going.
Let the benefit answer what the reader gets.
"Business Software Solutions" describes the company. "Send invoices from your phone" describes the outcome. The second version wins because a reader deciding whether to click is asking one question, what happens if I do this, and a benefit answers it directly while a description of the company leaves the reader to work it out themselves.
Write search ad headlines and descriptions that answer the query
A Google Ads listing gives you a small number of headline fields and description fields, each with a hard character limit, and Google will simply cut off or reject text that runs over. Count the actual text: run your draft through the length and character counter before you commit to a version. The discipline that matters more than the count is what you do with the space you have: put the search term, or something very close to it, in the first headline, and use the description to add the one benefit or objection-handler the headline had no room for.
Write social primary text for a reader who is scrolling.
A Meta or Instagram ad is competing with everything else in the feed, so the first line of the primary text does almost all the work: most readers decide whether to keep reading before the text is even fully expanded. Open with the benefit or the recognisable situation, not with the brand name or a general statement about the industry, because the brand name means nothing to someone who has never heard of you and a general statement gives them no reason to stop scrolling.
Keep a display banner to one message
A display banner is read at a glance, often while the reader is looking at something else entirely, so it can carry one idea and not much more: a short headline, perhaps one supporting line, and a CTA. Trying to fit a benefit, a second benefit, and a reassurance into a banner is the most common way display ads fail, because a reader who has half a second to look does not have time to process three separate points, however true each one is.
Choose emotional triggers that earn the click
A power word is a word chosen for the reaction it produces: "free", "guaranteed", "new", "proven". These words work because they short-circuit the reader's usual scepticism, but that is exactly why they need to be backed by something the ad can support. "Guaranteed results" on an ad for a service with no actual guarantee is not a stronger claim, it is an unsupported one, and the gap between what the word promises and what the business can back up is the gap the reader notices once they click through and it is also the gap the CAP Code exists to close.
Follow the CAP Code's rules for what an ad can claim
The CAP Code applies to UK advertising across search, social and display in the same way it applies to a poster or a television spot: claims have to be truthful, and claims that could be checked have to be capable of being backed up if the ASA asks. That covers superlatives ("the best", "the UK's leading"), price claims, and comparisons with named competitors, all of which are more common in ad copy than in other formats because ad copy is trying to make its case in so few words that a bold, unqualified claim is tempting.
For a fuller run-through of what the Code covers and how it tends to be applied, see the ASA and CAP plain-English guide. This is a practical summary for copywriters, not legal advice. For definitive guidance consult the CAP Code and the ASA's own resources.
Check the ad before it goes live
Before you commit budget to a headline, check it against a fixed set of criteria: run it through the headline scorer. The scorer checks the headline against the criteria it is built to test; it is a check, not a guarantee of how the ad will perform once it is live. Pair that with the character count for whichever platform you are writing for, since a strong headline that gets truncated halfway through a word is no longer the headline you wrote.