Plain Text vs HTML Email: Which Works Better for Ecommerce?

“Plain text emails get better deliverability” is one of the most repeated claims in email marketing. It is also one of the least evidenced. The truth is more useful: the format matters less than most people think for inbox placement, and more than most people think for how an email feels. For ecommerce, that second point is where the money is.

This guide covers the difference between plain text and HTML email, what the evidence actually says about deliverability and engagement, when plain text wins for ecommerce brands, and how to test both properly in Klaviyo.

---

Plain text vs HTML email: the short answer

HTML email supports images, layout, brand fonts, buttons and tracking; plain text is words and links only. For ecommerce, HTML wins for visual selling (launches, sales, product-led flows), while plain or plain-looking emails often win for personal moments (founder notes, check-ins, win-back). Deliverability depends far more on authentication and engagement than on format.

	Plain text	HTML
What it contains	Text and raw links only	Images, layout, fonts, colours, buttons
Looks like	A personal email	A designed brand email
Open tracking	Not possible in true text/plain	Yes (tracking pixel)
Click tracking	Limited	Yes
Renders consistently	Always	Needs testing (Outlook, dark mode)
Accessibility	Excellent for screen readers	Good if built with live text and alt text
Best for	Personal notes, replies, service messages	Campaigns, product-led flows, newsletters
Effort to build	Minutes	Design and QA time

---

What is the difference, technically?

A plain text email is sent with the content type text/plain: characters and line breaks, nothing else. No bold, no images, no hyperlinked words (links appear as full URLs).

An HTML email is sent as text/html, which is effectively a small web page rendered by the inbox.

In practice, almost every marketing email is multipart: it contains both an HTML version and a plain-text version, and the inbox displays whichever it supports or the reader prefers. Klaviyo automatically generates the plain-text part for emails built in the drag-and-drop editor, and you can edit it with Edit Plain Text Version.

That leads to the distinction that actually matters for marketers: designed HTML versus plain-looking HTML. Most “plain text” marketing emails are really simple HTML: one column, default-looking font, no header image, a signature. They look personal, but links and open tracking still work. Klaviyo’s text-only editor produces exactly this kind of email.

---

What the deliverability evidence actually says

This is where the internet gets overconfident, so here is what can be sourced (as of September 2026):

Mailbox providers do not penalise HTML as a format. Google’s email sender guidelines say that if messages are in HTML, they should be formatted to HTML standards, and warn against using HTML and CSS to hide content, which “might cause messages to be marked as spam.” That is a rule against sloppy or deceptive HTML, not against HTML.

Image-only emails are the real risk. Klaviyo’s help centre advises against image-only emails, noting that without alt text they can look suspicious to inboxes and land in spam. Email on Acid’s analysis makes the same distinction: images do not hurt deliverability by themselves, but emails that are entirely or mostly images can.

HubSpot’s tests found plain text drove more clicks. HubSpot’s widely cited study ran A/B tests on its own marketing emails. In its results, “the more HTML-rich an email was, the lower its open rate,” an HTML template with images had a 21% lower click-through rate than plain text, and a GIF version had a 2.3% lower click-through rate. The same article reports that in a 2014 survey nearly two-thirds of respondents said they preferred HTML and image-based emails. Three caveats before you rebuild your programme around it: these were HubSpot’s audience (B2B marketers), the tests are not dated, and open rates have been unreliable since Apple Mail Privacy Protection launched in 2021.

Klaviyo sees the same pattern on clicks. Klaviyo’s text-only email documentation says text-only emails “often see higher click rates than fully designed HTML emails,” particularly when signed by someone from the leadership team.

Gmail’s tabs are undocumented. You will read that plain-looking emails are more likely to land in Gmail’s Primary tab rather than Promotions. Google does not publish how its tabs classify mail, so treat that as a plausible side effect, not a strategy. Promotions tab placement is not spam, and plenty of ecommerce revenue comes from it.

What actually moves inbox placement: SPF, DKIM and DMARC authentication, low complaint rates, sending to engaged subscribers, and list hygiene. Format is a rounding error next to those. If your emails are landing in spam, start with our guide to why Klaviyo emails go to spam and the free email deliverability checker, not with stripping out your design.

---

When plain text wins for ecommerce

Plain-looking emails win when the reader should feel they are hearing from a person rather than a brand. In ecommerce flows, that is more often than people expect:

• Welcome email 2 or 3: the founder note. After the offer email, a short note from the founder about why the brand exists. Our welcome series framework places it here.
• Post-purchase check-in. “Your order should have arrived. How are you finding it? Just hit reply.” For supplement brands, this is a good way to catch confusion about dosing or timing early (keep it about the routine, not health outcomes). More in the post-purchase flow guide.
• Review requests that ask for a reply. A personal ask outperforms a big star graphic for many brands.
• Win-back notes. A short “we noticed you have not ordered in a while, anything we could do better?” email reads as sincere in a way a designed banner rarely does. See our win-back flow guide.
• Apologies and service issues. Delayed shipping, a stock problem or a site outage. Klaviyo’s own documentation lists apologies as a text-only use case.
• VIP and high-value outreach. A personal note to your best customers about early access.
• Wholesale and B2B follow-ups. Buyers expect business correspondence, not a promo layout.

The common thread is reply-worthiness. If you would be happy for the customer to reply, send it as a note.

---

When HTML wins

• Product launches and new arrivals, where the product has to be seen.
• Sales and promotions, especially around BFCM, where offer clarity and category navigation matter.
• Abandoned cart and browse abandonment, where a dynamic product image is the most persuasive element in the email.
• Newsletters and roundups, which rely on scannable modules.
• Anything with multiple products or choices, which plain text handles badly.

Our ecommerce email templates guide has layouts for each of these.

---

The middle ground: letter-style HTML

The best-performing format for many ecommerce flows is neither extreme: a letter-style email with a small logo or none, a single column of live text in a readable font, one inline image (or a single product), one link or small button, and a real signature. It keeps the personal feel of plain text with the tracking, accessibility and light branding of HTML. It also renders almost identically everywhere, which is more than most designed templates can say.

---

How to test plain text vs HTML in Klaviyo

1. Build both versions. Keep the subject line, preview text, send time and offer identical. Change only the format.
2. For campaigns, use Klaviyo’s A/B testing on the content, with a large enough sample for a meaningful result.
3. For flows, use a conditional or A/B split and let it run long enough to collect a meaningful number of recipients per branch.
4. Judge on the right metrics. Click rate, placed order rate and revenue per recipient, not open rate. Opens are inflated by Apple Mail Privacy Protection, and plain emails can look better on opens without earning more.
5. Check replies and unsubscribes. Plain-text notes often generate replies, which is a good engagement signal and valuable customer insight.
6. Re-test by email type. A result for a win-back note says little about a product launch.

Our guide to A/B testing email subject lines covers sample sizes and reading results; the same principles apply to format tests.

---

How to create a text-only email in Klaviyo

Per Klaviyo’s help centre (as of September 2026):

• Campaigns: create an email campaign, open the additional options menu (three dots) and choose Switch to text only editor.
• Flows: add an email to the flow, click Edit, and select Text only as the message content, or use Change template > Text Only on an existing email.
• What you can include: personalisation (such as first name), links, emoji, font style and colour changes, bullet and numbered lists, and images added through HTML image tags in source mode.
• Size limit: 1.05MB.

Writing tips: keep it short (100–200 words), write the way the sender actually talks, use one link, and sign with a real name. A plain email with five links and “SHOP NOW” in capitals is just a badly designed HTML email.

---

Is my email HTML or plain text?

• Visually: if it has images, coloured buttons, custom fonts or columns, it is HTML.
• In Gmail: open the message, click the three-dot menu and choose Show original. Look for Content-Type: text/html or text/plain.
• In classic Outlook: when composing, the Format Text tab shows whether you are writing in HTML, Plain Text or Rich Text. If replies arrive in plain text unexpectedly, that setting (or the sender’s) is usually why.

For mail merges from Outlook or Gmail, HTML is fine for short, personal-looking messages. Keep the formatting light so the merge looks like individual emails rather than a bulk send.

---

The bottom line

HTML and plain text are tools for different jobs. Use designed HTML where the product has to sell visually, use plain-looking emails where a human voice matters, always send multipart with a clean plain-text version, and ignore anyone who says format alone will fix your deliverability. Then test on your own list, measured on clicks and revenue.

If you want a Klaviyo programme where each email’s format matches its job, our email design and copywriting service writes and designs both. Or get a free Klaviyo audit and we will show you which flows would benefit from a more personal touch.