Core Features

Email HTML Validator, Client-Tested Live

It's high time to validate your email code, detect rendering issues, and improve inbox compatibility strongly. We have all you need inside the HTML checker.

truesend.io/html-checker

Live Analysis

email-template.html

1 <table role="presentation">

2 <tr><td style="padding:20px">

3 <h1 style="color:#2563eb">Welcome</h1>

4 <div style="display:flex">

5 <img src="hero.png" />

6 <a style="border-radius:8px">

7 </div>

8 </td></tr>

9 </table>

94%

Compatibility Score

Checked against 90+ clients

Gmail

100%

Apple Mail

100%

Outlook

78%

Yahoo

97%

Samsung

95%

flexbox not supported in Outlook

border-radius partial in Outlook

7 of 9 rules fully compatible

HTML Code Validation

No more code errors to affect your email. Our HTML checker stands by your side to check broken tags, unsupported CSS, and layout issues before you send.

Responsive Email Preview

Act smart and preview first how your emails will appear on desktop, mobile, and different screen sizes. No mistakes for later.

Compatibility Testing

At trueSend, you can easily check if your email is compatible with major inbox providers like Gmail, Outlook, and Yahoo Mail. It keeps every design consistent.

Auto-Fix Recommendations

Find instant solutions on how to fix HTML issues, improve deliverability, and optimize email performance.

How It Works

Check Your Email HTML in 3 Simple Steps

No hassle, just simple steps at Truesend. Launch flawless email campaigns and remove errors from the root.

Paste or Upload Your Email HTML

Open the HTML checker and upload your email template or code to it.

Scan for Errors & Compatibility Issues

You will see broken HTML, unsupported CSS, and layout problems right inside the checker.

Preview, Fix & Launch Your Campaign

Optimize your email layout, apply fixes, and you are ready to send emails with better inbox compatibility.

API Integration

Automate Email HTML Checks with API

Plug HTML validation straight into your workflow and let every email template get checked for errors, layout issues, and inbox compatibility before it ever reaches your audience.

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// Node.js HTML Checker API
const axios = require('axios');
const response = await axios.post(
  'https://api.truesend.io/v1/html-check',
    html: '<html>...your email...</html>',
    clients: ['gmail', 'outlook', 'apple_mail']
    headers: 
      'Authorization': 'Bearer ts_api_key'
console.log(response.data.score);
// → 94.5 (out of 100)
console.log(response.data.issues);
// → [{ client: "outlook", rule: "no-flexbox" }]

# Python HTML Checker API
import requests
response = requests.post(
    'https://api.truesend.io/v1/html-check',
    json={
        'html': '<html>...your email...</html>',
        'clients': ['gmail', 'outlook', 'apple_mail']
    },
        'Authorization': 'Bearer ts_api_key'
data = response.json()
print(data['score'])
# → 94.5 (out of 100)
print(data['issues'])
# → [{"client": "outlook", "rule": "no-flexbox"}]

// PHP HTML Checker API
$ch = curl_init
    'https://api.truesend.io/v1/html-check'
curl_setopt_array($ch, [
    CURLOPT_POST => true,
    CURLOPT_RETURNTRANSFER => true,
    CURLOPT_HTTPHEADER => [
        'Authorization: Bearer ts_api_key',
        'Content-Type: application/json'
    CURLOPT_POSTFIELDS => json_encode([
        'html' => '<html>...email...</html>',
        'clients' => ['gmail', 'outlook'
$result = json_decode(
    curl_exec($ch), true
echo $result['score'];
// → 94.5

Related Tools

Complete HTML Checker Toolkit

A complete set of built-in tools that work together to validate, test, and refine your email HTML before sending.

HTML Structure Scanner

Now, deep-scanning of your email code is simple. Fix broken tags, missing elements, and structural issues in minutes.

Email Rendering Preview Engine

Watch how your email appears across different screen sizes and email clients, and check spot layout issues early.

CSS & Compatibility Checker

Analyse CSS support and email client compatibility to tackle display problems for major inbox platforms.

FAQ

Frequently Asked Questions

Everything you need to know about TrueSend's HTML Email Checker

Why do my emails look different in Gmail and Outlook?

Gmail, Outlook, and other inboxes handle email HTML and CSS differently. But when you are using HTML Email Checker, you can test your email across major clients, spot display problems, and fix them before your email campaign goes out.

How do I know if my email HTML is broken?

You can run your HTML through a validator. It will instantly detect missing tags, CSS errors, and layout issues that break your email.

How can I test emails before sending campaigns?

You can test your email code errors, layout problems, links, and much more by running pre-send HTML checks. It is the simplest way to correct things before sending an email campaign.

Is automated email testing really necessary?

You cannot do it all manually. Automated email testing becomes highly important when you want consistent, error-free emails, especially for scaling email campaigns where errors increase.

Who should use an HTML Email Checker?

Every email marketer, developers, CRM teams, or SaaS companies that run regular email campaigns should use an HTML checker. It is helpful in sending clear and error-free emails that build trust and reputation.

Test and Optimize Email Code with HTML Checker