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We Tested AI Google Ads Copy Against the 30-Character Limit

Our AI ad tool wrote 6 of 10 Google headlines over the 30-character limit. One prompt change fixed length in every later test, but not invented claims.

By AIBizKit Editorial Team · Published November 9, 2026 · 2 min read

Key takeaways

  • ✓Before the fix, 6 of 10 AI-written headlines and all 6 descriptions were too long for Google Ads.
  • ✓Putting the limits next to the product details brought that to 0 of 16 in three separate checks.
  • ✓Length was the easy part. The model still used stock words and added claims nobody gave it.
  • ✓This is a small test of one model, so run your own count before you paste AI copy into Google Ads.

Google Ads will not save a responsive search ad headline over 30 characters or a description over 90, according to Google Ads Help. We measured how often the Ad Copy Writer on this site broke those limits, changed one thing, and measured again.

What we tested

The tool uses OpenAI's gpt-4o-mini model. Each test produced 16 lines of Google Search copy: 10 headlines and 6 descriptions, from two generations on the live site. A short script counted the characters in every line, spaces included. That script is the whole method, so anyone can repeat it by pasting AI output into a Google Ads Character Counter.

Results

  • Before the change (November 2026): 6 of 10 headlines over 30 characters, and 6 of 6 descriptions over 90.
  • After the change, check 1: 0 of 10 headlines over, 0 of 6 descriptions over.
  • After the change, check 2: 0 of 10 headlines over, 0 of 6 descriptions over.
  • After the change, November 9, 2026: 0 of 10 headlines over, 0 of 6 descriptions over.

The change that fixed length

We moved the numbers. The limits now sit in the same message as the product details, written out for the specific platform the user picked. Nothing has gone over since.

If you write prompts for ad copy, put this directly after your offer: "Headlines 30 characters or fewer, including spaces. Descriptions 90 characters or fewer. Count each one before answering."

What the fix did not solve

Every line in the November 9 test fit, and some of it still would not be worth running. Our inputs were soy candles and a standing desk converter. The output included these lines:

  • "Shop Now for Best Scents!" Nothing in the input said the scents were the best.
  • "Elevate your desk setup with our converter."
  • "Transform your workspace easily."

We had told the model not to use words like "elevate" and "transform" in the system prompt, and it used them anyway. An earlier run also added "Limited Time" to an offer with no time limit, which is worse than a stock word because it misleads the customer.

How far these results go

This is a small test: one model, three checks after the change, 16 lines each. It says nothing about ChatGPT's current models, Gemini, or Claude, and a different prompt could give different numbers. We are publishing it because the method is cheap and the failure was common enough to find on the first try.

A checklist before you paste AI copy into Google Ads

  1. 1.Count every headline and description.
  2. 2.Delete any claim your landing page does not prove: prices, deadlines, "best", guarantees.
  3. 3.Replace stock verbs with what the product does.
  4. 4.Read each headline alone, since Google chooses which ones appear together.

For the writing method, read How to Write Google Ads Headlines and Descriptions.

Sources

  • About responsive search ads, Google Ads Help, checked November 2026.
  • Test outputs: our own generations on aibizkit.tech. No user data was involved.

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Keep reading

Ad Hooks: 12 Opening Lines That Stop the ScrollTwelve patterns for the first line of a social ad or video, with examples for real product types and honesty rules that avoid clickbait.How to Write Google Ads Headlines and Descriptions (Responsive Search Ads)How responsive search ads work, the headline and description character limits, and a method for writing 15 headlines that combine well, with examples.How to Write Facebook Ad Copy That Gets ClicksA practical framework for Facebook and Instagram ad copy: hook, primary text, headline and call to action, how long each should be, and how to test them.

Written and reviewed by the AIBizKit editorial team. We update articles when platform rules change — if you spot something out of date, please let us know. Read our editorial standards.