Character limits per platform
Limits shape the writing. Google responsive search ads take up to 15 headlines of 30 characters and 4 descriptions of 90, with two 15-character display path fields, and count Chinese, Japanese and Korean characters as double width, so a Japanese headline holds about 15. Meta recommends about 125 characters of primary text for most placements, and longer text may be truncated. LinkedIn shows roughly the first 150 characters of intro text before cutting it off. Write to the visible length, not the maximum, and localise to the limit: a translated headline that runs to 34 characters is not a headline.
Meaningful variants, not near-duplicates
Responsive formats assemble ads from the lines you supply, so ten headlines saying the same thing in different words waste nine slots and weaken ad strength. Give each headline a job: the benefit, the proof, the offer, the objection answered, the audience named, the brand. Pin only what must appear, such as a regulated disclosure, because pinning cuts the combinations the system can test. Generation makes volume free, so the discipline moves to selection: a short list of distinct angles, each written well, then more variants of whichever angle wins.
Approved claims and banned words per market
Claims that are fine in one market are illegal in another. In the EU, foods may carry only health claims authorised under Regulation (EC) No 1924/2006, in wording close to the approved text. Prescription-only medicines cannot be advertised to the public in the EU or the UK. Financial promotions in the UK must be fair, clear and not misleading under FCA rules, and alcohol ads face their own codes. Keep a register per market of approved claims, required qualifiers and banned words, including competitor names and slang, and apply it to every variant before it reaches an approver.
Trademarks and superlatives
Google does not restrict competitors' trademarks as keywords, but restricts their use in ad text when the owner complains. In the EU, comparative advertising is allowed under Directive 2006/114/EC only if it compares like with like, objectively and verifiably, without denigrating or causing confusion. Objective superlatives such as 'best-selling', 'fastest' or 'number one' need evidence held before the ad runs (CAP Code rule 3.7 in the UK), while obvious puffery does not. Google's editorial rules also bar repeated punctuation such as '!!' and gimmicky capitals. Synthetic White enforces each brand's approved claims and banned words at generation, across ad copy in 30 languages.
Updated 25 September 2026