Latest / The Copywriting Podcast with Fexingo: Sales Letters, Headlines, and Persuasive Writing / How One Font Choice Made Readers Trust an Email
Transcript
- Lucas: So I want to talk about a split test that feels almost too obvious in hindsight but somehow still surprises most copywriters when they first hear the number. Luna: I'm ready. What's the number? Lucas: Sixty-three percent. That's the click-through rate lift a B2B SaaS company saw by switching the font in their email body copy from a sans-serif to a serif. Luna: Wait — just the font? Not the headline, not the offer, not the CTA button? Lucas: Just the font. Everything else identical. Same subject line, same offer, same layout, same sender name. They ran it on a list of about 47,000 subscribers in early 2024, and the serif version — I think it was Merriweather, a common web serif — beat the sans-serif version, which was Open Sans, by 63 percent on click-through rate. Luna: Okay, that's genuinely wild. But I have to ask — did the lift hold for the actual conversion, or was it just more clicks? Lucas: Great question. They tracked the full funnel, and the serif version also had a 34 percent higher conversion rate on the landing page. So it wasn't just clickbait — the readers who clicked were more engaged, or at least more likely to follow through. Luna: So what's the theory? Why would a serif font make someone more likely to click and buy? Lucas: The leading explanation comes from fluency theory — the idea that people perceive things that are easier to process as more true, more credible, and more familiar. And there's a solid body of academic research showing that serif fonts, especially in print or long-form digital reading, increase reading speed and comprehension slightly, but more importantly, they signal authority and tradition. Luna: Right, serifs are what we grew up reading in books and newspapers. There's a built-in cultural cue that says 'this is serious, this is trustworthy.' Lucas: Exactly. And in a B2B context, where the reader is evaluating a tool for their job, that trust signal matters a lot. The company in question was selling a project management platform aimed at mid-market teams — so decision-makers who are used to reading contracts, proposals, and white papers. Serif fonts feel like a document. Sans-serif feels like a social media post. Luna: But I've seen the opposite test work, too. A direct to consumer fashion brand I know tested a serif body font against their usual sans-serif and the sans-serif won by about 12 percent on click-through. Lucas: That's the critical nuance. The font effect is entirely contextual. For a fashion brand, sans-serif signals modernity, cleanliness, speed — the reader wants to feel like they're browsing a sleek store, not reading a textbook. Luna: So the same principle — fluency — cuts both ways. It's about matching the font to the reader's expectation of the genre. Lucas: Exactly. The B2B company succeeded because their audience expected a 'professional' reading experience. The fashion brand failed because their audience expected a 'contemporary' one. And if you get it wrong, you're not just losing a few points — you could be losing over half your click-throughs, like that 63-percent split shows. Luna: I want to dig into the actual execution. How did they structure the test? Was it a full email send, half and half? Lucas: It was an A/B test within their email platform — randomly split the list, send both versions at the same time, measure clicks and conversions over 72 hours. The serif version had a noticeably higher open rate too, by about 8 percent, which suggests the font choice might have influenced the decision to even open the email, not just click inside it. Luna: That's interesting — how could the font affect open rate when the recipient only sees the sender name and subject line before opening? Lucas: It can't directly. But a possible explanation is that the subject line and preview text were phrased in a way that hinted at a longer, more detailed email, and the serif font in the preview pane — on some clients — might have been visible. Or it could be random noise. But the click and conversion numbers are robust. Luna: Alright, so let's talk about the practical takeaway. If I'm a copywriter or a marketer listening, what do I do with this? Do I test serif versus sans-serif in every email? Lucas: Not every email. But if you're sending a long-form email — more than, say, 150 words of body copy — and your audience is making a considered decision, test it. Particularly if your brand already leans traditional or authoritative. And use a web-safe serif like Georgia or Merriweather, not something decorative that hurts readability. Luna: And if you're in e-commerce or fashion or entertainment, probably stick with your sans-serif and test other variables first. Lucas: Right. But the deeper lesson here is that every element of the page — including the typeface — communicates something. Copywriters spend so much time on the words, but the vessel those words arrive in is doing its own persuasion work. Luna: I think that's why this test is so compelling. It's not about a fancy new technique. It's about noticing something that's always been there, something as basic as the shape of the letters, and realizing it's a lever you can pull. Lucas: And it's a cheap lever, too. Changing a font takes five seconds. No new copy, no new design, no new offer. If it works, it's basically free money. Luna: That's the kind of insight that makes me glad we can go deep on these details without being interrupted by ads. Lucas: You know, that's actually something I've been thinking about. This show stays ad-free because of listeners who find value in these conversations and decide to support it. Luna: Yeah, it's a small thing, but it means we can spend an entire episode on one font test if we want to. Lucas: So if today's episode was worth a coffee to you, that's the link — buy me a coffee dot com slash fexingo. No pressure, no perks, just knowing the show stays independent. Luna: And we appreciate every single one. Now, back to that test — I want to ask about the email's length. How long was the body copy? Lucas: It was about 400 words. A fairly detailed case study summary with a link to the full story. So it was long enough that the reading experience mattered. Luna: That makes sense. For a short, punchy email — like a flash sale announcement — font probably doesn't matter as much because nobody's doing sustained reading. Lucas: Exactly. And that's the key insight: font choice is a credibility signal that works best when the reader has to invest cognitive effort. Short emails are scanned. Long emails are read. Serifs help the reader settle in. Luna: I also wonder about mobile. Was this test optimized for mobile? Because serifs can look terrible on small screens. Lucas: Good catch. The test was sent to both desktop and mobile, and the company reported that the lift was consistent across devices. But they used a font specifically designed for screen reading — Merriweather has a large x-height and generous letter spacing. So it's not just any serif; it's a screen-optimized serif. Luna: So the lesson is: if you test, test with a font that's built for the medium. Don't grab Times New Roman and expect magic. Lucas: Right. Times New Roman is a newspaper font designed for tiny columns of ink on cheap paper. On a screen, it's cramped and hard to read. Use Georgia, Merriweather, or even a slab serif like Roboto Slab if it fits your brand. Luna: Alright, so we've got the B2B win and the B2C counterexample. Are there other cases where serif outperformed sans-serif? Lucas: There's a well-known test from a nonprofit that sent a donation appeal email. They tested a serif body font against their usual sans-serif and saw a 22 percent increase in donations. The audience was older, the cause was serious — disaster relief — and the serif reinforced the gravity of the message. Luna: That aligns with the fluency theory again. When the message is emotionally heavy, the font can either support or undermine the tone. Lucas: Precisely. And that's the real takeaway: don't think of font as decoration. Think of it as part of the tone of voice. Serif says 'thoughtful, established, detailed.' Sans-serif says 'direct, modern, efficient.' Choose based on what your reader needs to feel to take the next step. Luna: I love that framing. It makes the decision less about aesthetics and more about psychology. Lucas: And it's testable. You don't have to guess. Run the split, let the data tell you which tone your specific audience responds to. That's the whole philosophy of this show, really — one small change, measured carefully, can reveal something big. Luna: Alright, so for anyone listening: pick one email you're sending this week, swap the body font, run a 50-50 test, and see what happens. And if you get a 63-percent lift, please write in. Lucas: We'd love to hear about it. And if you don't get a lift, that's data too. Either way, you'll know something you didn't know before.