What the preview can check
HTML Viewer Cat renders your template in your current browser. You can check text, spacing, image URLs and how the layout responds to width changes. It does not reproduce Gmail, Outlook or Apple Mail, including their CSS filtering and dark-mode adjustments.
Open your template
Need a starting point? Browse the free HTML email template library for account messages, receipts, newsletters and campaigns. Each design includes editable HTML, a plain-text version and notes on what to replace.
For a first project, edit a welcome email, a receipt or a newsletter. Each page opens its source in the viewer so you can change the real layout, then download your version.
- Open the example in the viewer, or paste your own email HTML into the editor.
- On a wide screen, choose phone or tablet in the preview toolbar to check narrower layouts.
- Use a custom width to check where text wraps or a column overflows. On a phone, the preview uses the available screen width.
- Open Download and choose HTML to save the edited source.
If your template is a file, open it from your device. Use the responsive testing guide to check overflowing columns and breakpoint gaps.
Share a layout for review
Use a PNG of the preview for a quick visual review, or save a PDF for a printable proof. These are review copies: send the downloaded HTML through your email provider and check the delivered email separately.
Check email-client support
CSS support varies between clients and versions. Check properties you rely on in Can I email’s compatibility tables. For example, flexbox support differs between Outlook for Windows and Outlook.com. A layout that works in a browser is not proof that it works in either client.
Inline styles and table-based layouts remain useful when supporting older clients. Use the requirements of your audience to choose an approach, then send test messages through the same service you will use for delivery.
Before sending
Sending a newsletter? Follow our MailerLite HTML import walkthrough, using a design from the marketing template collection.
- Replace placeholder text with the actual subject, headings and body copy.
- Use full HTTPS URLs for hosted images and links. Check the destination of each link.
- Check narrow screens, long text and images that fail to load.
- Test the delivered message in the clients and light or dark modes your audience uses.
A small example
This example uses inline styles and a single column. It is a starting point for editing, not a template verified across email clients.
<div style="max-width:600px; margin:0 auto;
font-family:sans-serif; color:#333;">
<h1 style="color:#1a1a1a;">
Welcome!
</h1>
<p style="line-height:1.6; color:#666;">
Thanks for signing up. Click the button
below to get started.
</p>
<a href="https://example.com"
style="display:inline-block; padding:12px 24px;
background:#007bff; color:#fff;
text-decoration:none; border-radius:4px;">
Get Started
</a>
</div>