What HTML errors does ValidateHTML check for?

ValidateHTML checks for unclosed tags, missing required attributes, deprecated HTML elements, incorrect tag nesting, missing DOCTYPE, invalid attribute values, accessibility issues, and more.

Is ValidateHTML free to use?

Yes, ValidateHTML is completely free. You can validate unlimited HTML code snippets and URLs at no cost. No registration required.

How is the HTML quality score calculated?

Your HTML quality score starts at 100. Each error deducts 10 points and each warning deducts 3 points. Grades: A (90-100), B (75-89), C (50-74), D (25-49), F (below 25).

Does HTML validation affect SEO?

Yes. Clean markup improves crawlability, reduces rendering errors, and ensures search engines can properly parse your content. Valid HTML also improves accessibility, which is increasingly important for SEO.

Open Graph Checker

Enter a URL to check its Open Graph tags. See how your page looks when shared on Facebook, Twitter, LinkedIn, and Slack.

What Are Open Graph Tags?

Open Graph (OG) tags are HTML meta tags that control how your page appears when shared on social media platforms like Facebook, LinkedIn, Twitter/X, Slack, Discord, and more. Without OG tags, platforms will try to guess your page title, description, and image — often with poor results.

When properly configured, OG tags ensure your content looks professional and compelling when shared, leading to higher click-through rates and more referral traffic from social media.

Essential Open Graph Tags

og:title

The title shown in social media cards. Keep it under 90 characters for best display.

<meta property="og:title" content="Your Page Title">

og:description

A brief description shown below the title. Keep it under 200 characters.

<meta property="og:description" content="A brief description of your page content.">

og:image

The image displayed in the card. Use 1200x630px for best results across all platforms. Must be an absolute URL.

<meta property="og:image" content="https://example.com/image.jpg">

og:url

The canonical URL for the page. Prevents duplicate content when the same page is shared via different URLs.

<meta property="og:url" content="https://example.com/page">

og:type

The type of content. Use 'website' for homepages, 'article' for blog posts, 'product' for e-commerce.

<meta property="og:type" content="website">

OG Image Best Practices

Size: 1200 x 630px

This aspect ratio works well on Facebook, LinkedIn, Twitter, and Slack.

File size under 5MB

Large images may not be fetched by some platforms. Keep it optimized.

Use absolute URLs

Always use the full URL (https://...) for og:image, not relative paths.

Add text to images

Include your title or key message on the image for maximum impact.

Twitter Card Tags

Twitter/X uses its own meta tags (twitter:card, twitter:title, twitter:description, twitter:image) but falls back to OG tags when Twitter-specific tags are missing.

For best results, set twitter:card to summary_large_image for a full-width image card, or summary for a smaller thumbnail. Our checker validates both Open Graph and Twitter Card tags.

Frequently Asked Questions

What are Open Graph tags?

Open Graph (OG) tags are HTML meta tags placed in the <head> of your page that control how your content appears when shared on social media platforms. They define the title, description, image, and URL shown in social cards on Facebook, LinkedIn, Slack, Discord, and other platforms. Without OG tags, platforms will try to guess your content, often with poor results.

What is the ideal Open Graph image size?

The recommended OG image size is 1200 x 630 pixels (1.91:1 aspect ratio). This works well across Facebook, LinkedIn, Twitter, and Slack. Keep the file size under 5 MB for reliable loading. Use absolute URLs (starting with https://) and common formats like JPG or PNG. For Twitter specifically, 1200 x 628px also works for summary_large_image cards.

Do I need Twitter Card tags if I already have Open Graph tags?

Not necessarily. Twitter/X will fall back to Open Graph tags when Twitter-specific tags are missing. However, you should at minimum include the twitter:card tag to control the card format (summary or summary_large_image). If you want different content on Twitter than other platforms, add twitter:title, twitter:description, and twitter:image as overrides.

How do I debug Facebook sharing issues?

Use Facebook's Sharing Debugger (developers.facebook.com/tools/debug/) to see exactly what Facebook reads from your page. It shows which OG tags are detected, any errors, and a preview of the card. You can also use the 'Scrape Again' button to force Facebook to refresh its cache when you update your OG tags.

Is this Open Graph checker free?

Yes, our Open Graph checker is completely free. Enter any URL to instantly see all detected OG tags, preview how your page looks on different social platforms, and identify missing or misconfigured tags. No registration required.