© 2026 MailViewr
FeaturesFAQBlogTry FreeInstagramYouTubeTwitterEmailPrivacy PolicyTerms
MailViewr - The No-Login HTML Email Preview Tool Developers Actually Use | Product Hunt
MailViewr - Free HTML Email Preview Tool
Free EditorEditorTemplatesDashboard
ArticlesCSS Support ReferenceEmail Clients
CSS Support MatrixClient Compat MatrixQuirks Database
AccuracyAbout
NewGet detailed QA reports for your emails — catch rendering issues across clients before you send.
Try QA reports →
✓ Free • No signup • Test instantly

HTML Email Preview Tool
Stop sending broken emails.
Test how they render first.

See exactly how your emails look in Gmail, Outlook, Apple Mail, and mobile—before a single subscriber sees them. Preview in dark mode, get an instant compatibility score, and send test emails straight to your inbox.

  • ✓ Paste HTML
  • ✓ Pick an email client
  • ✓ Preview
  • ✓ Send Test Emails
Test Your Email FreeHow it works ↓

Preview across real-world clients

See how the same HTML renders in Gmail, Outlook, Apple Mail, and more.

Catch layout breakages early

Spot spacing, alignment, and image issues before your audience does.

Move faster with fewer test sends

Iterate on your template without the 'send → check → fix' loop.

mailviewr.com/email-preview
MailViewr SaaSBrowser - software database
#1 ChatGPT
FP#7 FounderPal
600+ active monthly users
49 countries

Used by developers at

ring.iomysa.iomoppenheim.comflosek.comzerezes.com.bromnitel.esyoti.comdsv.comxperts.co.zacollegedunia.comlocalizejs.comand many more...ring.iomysa.iomoppenheim.comflosek.comzerezes.com.bromnitel.esyoti.comdsv.comxperts.co.zacollegedunia.comlocalizejs.comand many more...
Free email preview tool showing HTML email test in Gmail and Outlook
Full Feature Suite

Everything you need to send email with confidence

Email Preview

Free · No signup · Browser-based

  • ✓Gmail, Outlook, Yahoo Mail — web, iOS, Android
  • ✓Dark mode preview and testing
  • ✓CSS compatibility score with per-client error detection
  • ✓Inline CSS validation (style blocks + inline attributes)
  • ✓Device simulation — desktop, tablet, mobile, orientation toggle
  • ✓CSS inlining
  • ✓Send test emails to your inbox
  • ✓Pre-Send QA Report — 9 checks, score out of 100 (free account required)
Try Email Preview

Email Templates

6 free templates · Commercially licensed

  • ✓Newsletter, Promotional, Welcome, Transactional, Event Invitation, Announcement
  • ✓Fully responsive — tested across Gmail, Outlook, Apple Mail
  • ✓One-click copy to clipboard
  • ✓ESP integration guides: Mailchimp, SendGrid, Klaviyo, Brevo, HubSpot
  • ✓Handlebars.js, Jinja2, and Liquid variable syntax supported
Browse Templates
Free templates

DISCOVER
HANDY
TEMPLATES

Free HTML email templates with variables pre-tagged for Mailchimp, SendGrid, and Klaviyo. Preview in any email client before you send. Save time, look professional, and get perfect rendering every time.

See templatesCreate your own

NEWSLETTER

Newsletter Template

PROMOTIONAL

Promotional Email Template

WELCOME

Welcome Email Template

TRANSACTIONAL

Transactional Email Template

EVENT

Event Invitation Template

ANNOUNCEMENT

Product Announcement Template

→
View all
templates

ALL TYPES

Rendering Accuracy

See exactly
how it renders

35% of email opens now happen in dark mode. Every email client inverts colors differently — Gmail Android does full CIELAB inversion, Outlook applies partial overrides, Apple Mail uses HSL transforms. MailViewr runs each client's actual algorithm in your browser, so what you see matches what your subscribers see.

100%
Desktop accuracy (all clients)
90–95%
Light mode mobile accuracy
14
Client + theme combinations tested

Gmail Desktop

Chrome · Safari · Firefox

Dark mode97%
Light mode97%

Gmail Android

Mobile app

Dark mode~90%
Light mode97%

Gmail iOS

Mobile app

Dark mode75–80%
Light mode95%

Outlook Desktop

Chrome · Safari · Firefox

Dark mode100%
Light mode100%

Outlook Android

Mobile app

Dark mode~70% · beta
Light mode98%

Outlook iOS

Mobile app

Dark mode70–75% · beta
Light mode97%

Outlook mobile dark mode uses undocumented color override logic. Desktop and light mode accuracy is verified against real device recordings. How we measure accuracy →

Pre-Send QA Report
90/100
Issues Found2 checks failed · fix before sending
  • Gmail Clipping Risk
  • Unsubscribe Link Present
  • No Image-Only Content
  • Alt Text on All Images−5pts
  • No External Stylesheets
  • DOCTYPE Declaration
  • Structural Tags (html/head/body)
  • No Placeholder Hrefs−5pts
  • Viewport Meta Tag
SpamAssassin Score2.4 / 5.0  ✓ Pass

Pre-Send QA Report

Catch problems before you hit send

Run 9 structural checks and a SpamAssassin spam score analysis on your HTML email and get a readiness score out of 100. From Gmail clipping to missing unsubscribe links — see exactly what to fix, before your subscribers do.

  • Gmail clipping risk (102KB limit)
  • Missing unsubscribe link (CAN-SPAM / GDPR)
  • Image-only email detection
  • Alt text on every image
  • No external stylesheet links
  • Placeholder href detection & link audit
  • Missing viewport meta tag
  • DOCTYPE declaration check
  • Structural tags (html / head / body)
  • SpamAssassin spam score + per-rule breakdown
Run QA Report — it's free

Requires a free account · takes under 5 seconds

Email Preview Tool FAQ

Common questions about HTML email testing, Gmail and Outlook rendering, and how MailViewr works

General

What is an email preview tool?
It helps you see how your HTML email will look in different email clients and devices before you send it. This eliminates guesswork and reduces the risk of sending broken emails.
Is MailViewr free to use?
Yes! MailViewr is completely free. You can preview your HTML emails across multiple clients without any cost or signup required.
Do I need to create an account?
No account is required. Simply paste your HTML and start previewing immediately.

Email Rendering

Why does my email look fine in my builder but broken in Outlook?
Email clients don't share the same HTML/CSS support. Outlook desktop uses Microsoft Word's rendering engine, which ignores many modern CSS properties like flexbox, grid, and certain padding/margin rules.
Which email clients does MailViewr support?
MailViewr supports previews for Gmail (web, Android, iOS), Outlook (desktop, web, mobile), Apple Mail, Yahoo Mail, and other popular clients.
Why do colors look different in dark mode?
Some email clients automatically invert or adjust colors in dark mode to improve readability. This can affect backgrounds, text, and images. Always test dark mode previews to ensure your design remains readable.
Why aren't my web fonts showing?
Most email clients don't support web fonts. Gmail, Outlook, and Yahoo will fall back to system fonts. Always specify fallback font stacks like 'Arial, Helvetica, sans-serif'.

Best Practices

Do I really need previews if my ESP already shows mobile/desktop views?
Those previews often represent devices, not real client rendering quirks. Client-specific previews reveal where Gmail vs Outlook behaves differently, catching issues ESP previews miss.
What should I test first?
Start with a high-impact combo: Gmail (mobile) and Outlook (desktop). If it works there, you'll catch most common breakages early. Then expand to Apple Mail and other clients.
Should I use tables or divs for email layouts?
Tables are still the most reliable choice for email layouts. While modern clients support divs, Outlook desktop requires table-based layouts for consistent rendering.
How do I make my emails responsive?
Use fluid tables with percentage widths, media queries where supported, and mobile-first design. Test thoroughly since media query support varies by client.

Technical

Can I preview emails with external images?
Yes, MailViewr will load and display external images in your preview. Make sure your image URLs are accessible and use HTTPS for best compatibility.
Is my email HTML stored or shared?
No. Your HTML is processed locally in your browser and is not stored on our servers. Your email content remains private.
What CSS properties should I avoid?
Avoid flexbox, grid, position: absolute/fixed, advanced selectors, and CSS variables. Stick to inline styles, basic padding/margin, and table-based layouts for maximum compatibility.
Does MailViewr check if my email will go to spam?
Yes. The Pre-Send QA Report includes a SpamAssassin spam score check. SpamAssassin is the industry-standard open-source spam scoring engine used by most mail servers. MailViewr runs your HTML through it and returns your score, the 5.0 pass/fail threshold, and a per-rule breakdown so you can see exactly what's triggering flags.
What is a good SpamAssassin score for email?
Aim for under 2.0 — that's considered clean. Scores below 5.0 pass most mail servers' default threshold. Scores between 5.0 and 7.9 will be flagged or filtered, and scores of 8.0 or above are typically rejected outright. The SpamAssassin check is included free in every QA Report.
Why does my SpamAssassin result show rules like NO_RECEIVED, MISSING_DATE, or MISSING_MID?
These are expected when testing in a preview tool. MailViewr submits your HTML directly — not through an SMTP server — so there are no routing headers, timestamps, or Message-ID headers. Real sends via any ESP (Mailchimp, SendGrid, etc.) automatically add these headers, so they won't fire on actual campaigns. They carry 0 or negative scores and are flagged as expected in the results panel.
Does the SpamAssassin score affect my QA Report score out of 100?
No. The SpamAssassin check is a separate, informational section. Only the 9 structural checks (Gmail clipping, missing unsubscribe link, alt text, etc.) contribute to your score out of 100. The spam score is shown alongside so you have the full picture before sending.
What are the BAYES rules in the SpamAssassin breakdown?
BAYES rules are SpamAssassin's Bayesian classifier — it analyses word patterns in your email statistically. BAYES_00 means it's 99%+ confident the email is not spam (very beneficial). BAYES_99 means it's almost certain it is spam. For marketing emails, keeping your content clear and avoiding spam-like language helps keep the Bayesian score low.
What does URIBL_BLOCKED mean in my SpamAssassin results?
URIBL_BLOCKED means a DNS blocklist query was blocked by the server environment — it does not mean your domain is on a blocklist. This is a common result in sandboxed or preview environments like MailViewr and is not a real spam signal for your email. It should be ignored for testing purposes.