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Hey, Grow Newsie reader!
Here's the truth: Running your newsletter on intuition alone leaves money on the table. When you're sending to thousands of subscribers, even a 1% improvement in your open rate or click-through rate compounds into significant growth over time.
A/B testing (also called split testing) removes the guesswork. Instead of wondering which subject line works better, you test both versions with real subscribers and let the data decide.
The ROI is real: Newsletter operators who regularly A/B test report open rate increases of 10-25% and click-through rate improvements of 5-15% within just a few months of consistent testing.
The Golden Rule: Test One Variable at a Time
Before we dive into what to test, here's your most important rule: Only change one element per test.
If you simultaneously test a new subject line AND a new send time, you'll never know which change drove the results. Keep everything else constant, modify just one variable, and you'll get clean, actionable data you can trust.
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What to Test First: The Priority List
Not all A/B tests are created equal. Some elements have massive impact; others barely move the needle. Here's your priority order based on what delivers the biggest wins:
1. Subject Lines (START HERE)
Why test first: Your subject line is the gatekeeper. If subscribers don't open your email, nothing else matters. Subject lines typically have the highest impact on open rates.
Test ideas to try:
Word order: Does "Save 25% Today" beat "Today Only: 25% Off"? Front-loading the benefit often wins.
Length: Test short (3-5 words) vs. longer descriptive lines (8-12 words)
Personalization: Adding the subscriber's first name can increase opens by 14%+
Tone: Professional vs. conversational vs. curiosity-driven
Emojis: One emoji vs. none vs. multiple
Question format: "Want to Double Your Email List?" vs. statements
Pro tip: If you send newsletters with multiple stories or links, test featuring different content pieces in your subject line to learn what topics resonate most.
2. Preheader Text
Why test second: The preheader appears right after your subject line in most email clients. It's basically a second subject line that can boost opens significantly—yet many newsletters ignore it entirely.
Test ideas to try:
Complementing vs. repeating your subject line
Length: short (30 characters) vs. long (90+ characters)
Call-to-action driven vs. content preview
Using emojis or special characters
Example test:
Version A: "Spring New Arrivals 🌸"
Version B: "Explore Our Unisex Collection | Loyalty Discounts Inside"
3. Send Time and Day
Why test third: Timing dramatically affects whether your newsletter gets seen or buried under 50 other emails.
Test ideas to try:
Morning (6-9 AM) vs. lunch (11 AM-1 PM) vs. evening (6-9 PM)
Weekdays vs. weekends
Tuesday (statistically the most popular day) vs. your current schedule
Early week vs. end of week
Important: Give each time slot at least 2-3 weeks of testing before drawing conclusions. Seasonality and external factors can skew single-test results.
4. From Name
Why test fourth: The "from" name builds trust and recognition. It's one of the first things subscribers see.
Test ideas to try:
Company name vs. founder/individual name
First name only vs. full name
Personal name + company (e.g., "Sarah from Grow Newsie")
Different team members (if you have multiple contributors)
Reader insight: In the Twitter age, readers often connect more strongly with individual voices than faceless brands. Testing personal names can surprise you with significantly higher engagement.
5. Call-to-Action (CTA)
Why test fifth: Once someone opens your newsletter, your CTA determines whether they take action or ghost you.
Test ideas to try:
Button vs. text link
Placement: above the fold vs. bottom of email vs. both
Wording: "Get Started" vs. "Try It Free" vs. "Learn More"
Color: bold colors vs. subtle vs. your brand color
Size: prominent vs. understated
Punctuation: "Start Now" vs. "Start Now!"
Secondary Tests (After You've Nailed the Basics)
Once you've optimized your subject line, preheader, timing, from name, and CTAs, you can experiment with these elements:
Design and Format
Plain text vs. HTML design vs. hybrid
Single column vs. two-column layout
Image-heavy vs. text-focused
Short emails vs. long-form content
Content Variations
Number of links/stories (5 vs. 10 vs. 15+)
Content order (what you feature first)
Tone (professional vs. conversational vs. humorous)
Personalization beyond names (location, interests, behavior)
Visual Elements
Images vs. no images
GIFs vs. static images
Different image styles (screenshots vs. illustrations vs. photos)
Alt text optimization
How to Set Up Your First A/B Test
Step 1: Define your hypothesis Don't just randomly test things. Use this framework:
"I believe that [CHANGE] will increase [METRIC] because [REASONING]."
Example: "I believe that adding the subscriber's first name to the subject line will increase open rates because personalization makes emails feel more relevant."
Step 2: Determine your sample size
Minimum list size: 5,000 subscribers (smaller lists won't give reliable results)
Test split: Use 10-20% of your list for testing (5-10% per variant)
Winner gets the rest: Send the winning version to the remaining 80-90%
Step 3: Choose your success metric
Subject line tests → Measure open rate
CTA tests → Measure click-through rate
Content tests → Measure engagement time or clicks on specific links
Step 4: Set test duration
Minimum: 1-2 hours (lets both groups receive and potentially open)
Ideal: 4-24 hours depending on list size and engagement patterns
For timing tests: Run for 2-4 weeks to account for weekly patterns
Step 5: Analyze and implement Most email platforms calculate statistical significance automatically. Look for:
A clear winner (not a 1-2% difference—aim for 5%+ improvement)
Statistical significance (usually shown as a confidence level of 95%+)
Consistency over multiple tests before making it your default
Common A/B Testing Mistakes to Avoid
❌ Testing too many things at once → You won't know what caused the change
❌ Ending tests too early → Not enough data = unreliable results
❌ Testing on a tiny list → Under 5,000 subscribers makes results meaningless
❌ Never testing again → Your audience evolves; keep testing quarterly
❌ Ignoring mobile → 50%+ of emails are opened on mobile; test mobile rendering
❌ Testing and forgetting → Document what you learn for future campaigns
Your A/B Testing Action Plan
Week 1-2: Run 2-3 subject line tests
Week 3-4: Test preheader text variations
Week 5-6: Experiment with send times
Week 7-8: Test from name options
Week 9-10: Optimize your CTAs
By Week 10, you'll have data-backed insights on all five high-impact elements. Most newsletter operators see a 15-30% overall improvement in engagement metrics after completing this testing sequence.
Tools to Make Testing Easier
Most email service providers include A/B testing features:
Mailchimp, ConvertKit, MailerLite: Built-in A/B testing with automatic winner selection
Beehiiv, Substack: Subject line testing available
Manual approach: Split your list manually and track results in a spreadsheet (works for any ESP)
Pro tip: Track all your test results in a simple spreadsheet with columns for: Date, Element Tested, Version A, Version B, Winner, and Improvement %. This becomes your playbook for future campaigns.
The Bottom Line
A/B testing isn't optional anymore—it's how serious newsletter operators separate themselves from the pack. Start with subject lines, move through the priority list systematically, and watch your open rates and click-throughs climb.
The best part? Every test teaches you something about your audience. Over time, you'll develop an intuitive sense of what works for YOUR specific readers, not just what works "in general."
Your homework: Pick ONE element from the priority list above and run your first test this week. Reply to this email and let me know what you're testing—I'd love to hear your results!
Keep growing!
With love,
Nikhil
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