Why A/B Testing could be the most valuable thing you do for your donor communications

If your emails and landing pages aren’t performing quite as well as you hoped, don’t assume they need a complete overhaul. You might just need to start testing.

When resources are tight and every message matters, A/B testing is one of the most cost-effective ways to learn what your supporters truly respond to. It’s the closest thing we have to a “fundraising microscope”, showing you not what you think will work, or what audiences say will work, but what actually does.

Get excited (but also don’t)

The first thing is to get simultaneously excited about A/B testing, and NOT getting excited about A/B testing. It’s at the same time both understanding the potential that testing can uncover a world-changing insight that has great revenue potential, but also knowing that the majority of the time, A/B tests either:

• don’t have a statistically significant result that can be actioned without retesting, or
• confirm what is already known and in-market.

With this see-saw of optimism and realism, guidelines around testing are needed. 

Rather than say ‘let’s test it’, ask first ‘why are we testing it? Why do we think this will change a donor’s behaviour?’

That is, you need a hypothesis to create clarity, incorporate and communicate the goal of your test, and provide reasoning for why the test is needed. Your hypothesis can be formatted like:

We believe that [doing this] for [these people] will achieve [this outcome/impact] because [psychological principle / behavioural theory / element].

The small changes that make a big difference

Once you have an idea of what you’re testing and why, I have more good news: the beauty of A/B testing is that you don’t have to reinvent your campaigns. 

Sometimes it’s as simple as a different sender, a shorter subject line, a new image, or a shifted CTA to unlock double-digit growth in engagement or conversions.

Image: Email banner A/B test between banner images for The Kids Cancer Project’s K’Day appeal

Over time, these small lifts compound, turning incremental improvements into significant revenue gains.

5 A/B test ideas for email and SMS

• Banner vs no banner in lead generation emails
• Authority sender voice vs relatable sender voice in donor acquisition emails or SMS
• Testing CTA buttons text, such as ‘Sign up’ vs ‘Get started’ in fundraising acquisition emails
• Mention previous amount or don’t mention previous donation amounts in second gift emails
• Donation ask variants in second gift communications
  • Lower than previous gift
  • Higher than previous gift

Beyond the numbers: building supporter relationships

While it’s tempting to see A/B testing as purely a numbers game, the real win is how it deepens your understanding of supporters:

• What messages spark curiosity or urgency
• Which stories inspire trust and action
• How timing and tone influence generosity
• Who is communicating and their existing levels of trust

Every test that uncovers a new learning (or confirmation of prior learnings!) brings you closer to creating journeys that feel personal, relevant, and rewarding for potential and current donors and fundraisers.

The risks of guessing

Without testing, campaign decisions often come down to gut feel or “what worked last year.” That’s risky in a changing digital environment, especially when donor expectations shift faster than appeal calendars.

A/B testing removes that risk by replacing assumption with evidence. You don’t have to guess; your supporters will tell you, through their behaviour, what works best.

We’ve seen a wide range of results across similar kinds of campaigns (such as community fundraising in the below examples for PCFA…

…and seen different results for SCHF for the same kind of event.

Your next step

If you’re ready to start building stronger, more responsive supporter journeys, we’ve created The Ultimate A/B Testing Guide for Online Fundraising — an 8-page, step-by-step workbook to help you:

• Know what to test
• Set up an a/b test
• Discover a/b testing tools
• And run and document your tests

It’s everything you need to stop guessing and start growing.

And right now, there’s even more reason to act:

📅 Until the end of October 2025, Marlin Communications is offering a limited time offer of 50% off all new:

• Journey review & workshop packages
• Donor journeys
• Regular giver journeys
• New subscriber welcome journeys
• Email or landing page A/B tests

This isn’t just about reviewing emails or testing for the sake of testing. It’s about:

• Reviewing your audience profiles, personas, and engagement strategy
• Mapping high-performing journeys for your supporter segments
• Aligning email, CRM, and SMS channels to deliver the right message, at the right time
• Creating a phased test-and-learn plan to boost your KPIs long term

Send us a brief today to secure your discount and start building the supporter journeys your community and cause deserves.