How to Write Google Ads That Actually Convert: RSA Best Practices

The Anatomy of a Responsive Search Ad

Since Google sunset Expanded Text Ads in 2022, Responsive Search Ads (RSAs) are the only text ad format in Google Search. Understanding how they work is critical to writing ads that convert.

An RSA consists of:

• Up to 15 headlines (max 30 characters each)
• Up to 4 descriptions (max 90 characters each)
• Display URL paths (two fields, max 15 characters each)
• Final URL (the landing page)

Google dynamically assembles combinations of your headlines and descriptions, testing different arrangements to find what performs best. The system shows up to 3 headlines and 2 descriptions at a time.

How Google Assembles Your Ad

When someone searches, Google picks a subset of your headlines and descriptions to show. It considers:

• Relevance to the search query — Headlines containing the searched keyword are favored
• Historical performance — Combinations that have earned clicks before are shown more often
• Ad position — More headlines and descriptions may show in top positions
• Device — Mobile ads may show fewer headlines due to screen size

This means every headline and description must work independently — any of them could be shown alongside any other. They must also work well together as a group.

Headline Writing Formulas

With 15 headline slots and 30 characters each, you need a strategic approach. Here are proven formulas:

Formula 1: Keyword Match Headlines (3-4 headlines)

Include your target keyword directly in the headline. This is the single most important factor for ad relevance.

• "Emergency Plumber London"
• "24h Plumbing Service London"
• "Plumber in London — Fast"

Formula 2: Benefit Headlines (3-4 headlines)

Highlight what the customer gains.

• "Fixed Price — No Surprises"
• "Same Day Service Available"
• "5-Star Rated on Google"

Formula 3: CTA Headlines (2-3 headlines)

Tell the user what to do next.

• "Call Now for a Free Quote"
• "Book Online in 2 Minutes"
• "Get Your Free Estimate"

Formula 4: Trust & Proof Headlines (2-3 headlines)

Build credibility.

• "15+ Years of Experience"
• "Licensed & Fully Insured"
• "500+ 5-Star Reviews"

Formula 5: Urgency Headlines (1-2 headlines)

Create time pressure.

• "Limited Slots This Week"
• "Available Right Now"

Writing Effective Descriptions

Descriptions give you 90 characters — three times the space of a headline. Use them to expand on your value proposition.

Description Best Practices

• Start with the strongest benefit — The first description line gets the most visibility
• Include a CTA — "Call today", "Book now", "Get your free quote"
• Add specifics — Prices, timeframes, guarantees ("From €49 | Same-day service | Money-back guarantee")
• Use all 4 slots — More descriptions give Google more combinations to test

Description Examples

• "Professional plumbing services in London. Fixed prices, no call-out fee. Available 24/7 for emergencies. Call now for a free quote."
• "Trusted by 500+ customers. Licensed, insured, and guaranteed. Book your appointment online in 2 minutes — or call us anytime."

Pin Positions: When and How to Use Them

Pin positions let you lock a headline or description to a specific position. A pinned headline always appears in position 1, 2, or 3.

When to Pin

• Pin your keyword headline to position 1 — Ensures the most relevant headline always shows first
• Pin your CTA to position 3 — Ends the ad with a clear call to action
• Pin your strongest description to position 1 — Guarantees it is always visible

When Not to Pin

Do not pin everything. Over-pinning restricts Google's ability to test combinations and can hurt your Ad Strength score. Pin 2-3 headlines maximum and leave the rest flexible.

Character Limits: Working Within Constraints

Headlines: 30 Characters

Thirty characters is tight. Common words eat into your limit quickly:

• "Emergency Plumber London" = 25 characters (fits)
• "Emergency Plumber in London" = 27 characters (fits)
• "Emergency Plumbing Services London" = 34 characters (too long)

Tips for staying under 30 characters:

• Drop articles ("a", "the", "in")
• Use abbreviations ("24h" instead of "24 hours")
• Use symbols ("&" instead of "and")
• Shorten city names if well-known ("NYC" instead of "New York City")

Descriptions: 90 Characters

More room to work with, but still requires concise writing. Avoid filler words and get to the point quickly.

Display Paths: 15 Characters

Display paths appear after your domain in the ad URL (e.g., example.com/plumber/london). They should reinforce the keyword and landing page topic.

Common Ad Copy Mistakes

Mistake 1: Generic Headlines

"Welcome to Our Website" or "Professional Services" tell the user nothing about what you offer. Every headline should be specific to the keyword and value proposition.

Mistake 2: No Keyword in Ad Copy

If someone searches "emergency plumber London" and your ad headline says "Home Repair Experts", you lose the relevance connection — and your Quality Score drops.

Mistake 3: All Headlines Sound the Same

Having 15 variations of "Best Plumber in London" wastes your headline slots. Use the formula categories above to diversify your message.

Mistake 4: Ignoring Ad Extensions

Sitelinks, callouts, structured snippets, and call extensions add extra information to your ad. They increase your ad's visual footprint on the page and can significantly improve CTR.

Testing and Measuring Ad Performance

Key Metrics to Track

• CTR (Click-Through Rate) — Are people clicking your ad? Industry average for Search is 3-5%.
• Conversion Rate — Are clicks turning into customers?
• Cost Per Conversion — Is the cost sustainable for your business?
• Ad Strength — Google's rating of your RSA (Poor, Average, Good, Excellent)

How to Test RSAs

Since Google dynamically combines your headlines and descriptions, traditional A/B testing is limited. Instead:

1. Monitor the Combinations Report in Google Ads to see which headline/description pairings perform best
2. Replace underperforming headlines with new ones every 4-6 weeks
3. Test different value propositions across ad groups