What is an email template checker?
An email template checker is a tool for previewing how an email looks before you send it. Instead of finding out that your layout breaks after the campaign is already out, you catch the problem in a preview and fix it first.
The job is to surface the inconsistencies that come from how differently each email client reads HTML and CSS. A checker flags problems like broken images, missing alt text, font substitution, and collapsed buttons before they reach a recipient. It shows you what your email looks like before it ships, not just what your design tool assumes. That matters most for automated flows, which fire continuously: a broken campaign sends once and you catch it in the metrics, but a broken flow template keeps sending until someone notices.
Why email rendering is so unpredictable
Email clients don't share a single standard for displaying HTML and CSS, so each one can interpret the same code a little differently. Older desktop versions of Outlook are known to render with a different engine than most clients and to drop CSS properties that work elsewhere. Some clients strip embedded styles.
A button styled with CSS padding can look clean in one client and collapse in another, where a smaller click target can pull conversions down with it. Across desktop clients, webmail, and mobile apps, you're designing for a wide range of rendering environments at once.
A few of the benefits of checking templates before you send:
- No broken sends to subscribers: you see layout collapse, missing images, and dead buttons in a preview, not in the replies.
- Flows that stay correct at scale: templates that power always-on automations are verified before they run on thousands of recipients.
- Protected campaign investment: the hours spent on copy, design, and strategy don't get wasted on an email that arrives broken.
Why choose Klaviyo for template checking
Klaviyo is the autonomous B2C CRM, so building, previewing, and sending happen in one place instead of across disconnected tools. You design an email with responsive templates, preview it with real customer data, send a test to your own inboxes, and launch the flow without exporting HTML or switching systems. Checking becomes part of building rather than a separate step you skip under deadline pressure.
Build and preview in the same editor
Klaviyo's drag-and-drop email editor uses responsive, mobile-ready templates and universal content blocks, so you can preview the desktop and mobile layout and catch problems while you're still designing.
Test personalisation before it ships
Because your customer data lives in the same system, you can preview an email with real profile data and confirm the fallbacks work, so a missing first name never renders as an empty space or a raw merge tag.
Launch email and text from one system
Email and text messaging run on the same platform, so the email you just checked launches into a flow that can coordinate both channels, no second tool, no second data set to keep in sync.
Key features of template checking in Klaviyo
Feature | Description | Available with Klaviyo |
|---|---|---|
Drag-and-drop editor | Build emails with responsive, mobile-ready templates and universal content blocks | ✅ |
Live personalisation preview | Preview an email with real profile data and confirm fallbacks before sending | ✅ |
Dynamic content blocks | Pull live catalogue data so prices and products stay current at send time | ✅ |
Built-in flows | The templates you build and preview power welcome, abandoned cart, post-purchase, and other always-on automations | ✅ |
One system for email and text | Build, check, and launch across email and text messaging on a single customer profile | ✅ |
How to get started with Klaviyo
To check your templates inside Klaviyo before you send:
- Build in the editor. Design your email with responsive templates and content blocks so it's mobile-ready from the start.
- Preview with real data. Send a test to a profile with no first name stored, and confirm your personalisation fallbacks hold.
- Click every link. Confirm each URL resolves and your tracking parameters are intact before launch.
- Send a test to real inboxes. Open it in the clients your subscribers actually use, on your phone and desktop, and scroll the whole message.
- Launch the flow. Once the template checks out, turn on the automation so every triggered send goes out from the version you already previewed and tested.
Building, previewing, and testing in one editor is part of why brands on Klaviyo see an average of 63x ROI on email. Want to preview your email before you send it? Get started with Klaviyo today.