Schema Markup Validator

Check what schema.org structured data a page has and whether the JSON-LD looks correct before publishing.

What does the Schema Markup Validator tool do?

This tool analyzes a page or pasted code and extracts structured data in JSON-LD format.

It shows what schema types were used and whether the structure is logical and matches the schema.

In practice, it works as a quick overview of schema.org markup implementation for SEO and rich results.

• Detects and lists the types of structured data present on the page.
• Displays extracted JSON-LD blocks for analysis.
• Checks JSON syntax correctness and basic JSON-LD structure.
• Highlights common issues and empty fields in schema objects.
• Shows errors based on the official schema.org recommendations in a practical way.

How does the Schema Markup Validator help SEO specialists and website owners?

For SEO implementations, speed and repeatability of verification matter. This tool simplifies it.

In a few seconds you can see if the structured data implementation makes sense and whether there are any empty fields.

• You save time. Verification usually takes less than a minute per page.
• You reduce the risk of implementation errors thanks to field and type checks.
• You make technical audits and content quality control before publishing easier.
• You help search bots better understand your content. This helps with SERP features.
• You get a clear preview of whether the JSON-LD implementation matches the page’s intent.

1. Analyze the page or source code without logging in to a CMS.
2. See detected schema types and their count within the document.
3. Get a list of issues and warnings with context for type and element.
4. Improve implementation and retest until you get a clean result.

Common use cases of the Schema Markup Validator tool

The tool is useful for audits, migrations, and daily control of structured data.

• SEO competition analysis. Check what schema types are used by top 10 sites.
• Schema.org implementation validation before publishing or deploying changes.
• Quality control after deployment. Detect empty fields and missing properties.
• Content review for rich results, rich snippets, and better query matching.
• Debugging JSON-LD errors when working with templates and scripts.

It is also useful for temporary or staging sites. Paste mode helps when the site is unavailable.

Comparison of the Schema Markup Validator with other tools

Functionality	DiagnoSEO	Other tools
Detection of what schema types are used on the page	✅	✅
Validation of JSON syntax and basic JSON-LD verification	✅	✅
List of warnings and issues with type and element context	✅	❌
Issue indication according to official schema.org recommendations	✅	❌
Ability to analyze by URL and by pasted code	✅	✅
Readable preview of extracted JSON-LD blocks	✅	❌

Tips and best practices

Structured data should describe content that is actually visible on the page.

• Keep schema type consistency with the subpage goal and user intent.
• Avoid empty values. Empty fields often generate warnings.
• Ensure correct formatting of dates, prices, and currencies. This is a common JSON-LD mistake.
• Maintain clear context and identifiers. This helps with data consistency.
• Compare the result before and after implementation. It helps track changes in releases.

If you work in multiple markets, keep property names and formatting consistent.

Most common errors

• Errors in JSON syntax. Missing comma, wrong quotation mark, or unclosed bracket.
• Missing required fields for a given type. For example, missing name or date.
• Empty fields. The tool will show them as warnings to fix.
• Schema type doesn’t match the page. This lowers trust in your structured data.
• Duplicate objects of the same type on a single subpage without justification.

How to use the Schema Markup Validator tool

1. Select analysis mode. You can use a URL or paste the page’s code.
2. If you’re testing a URL, paste the subpage address and run validation.
3. If you’re testing code, paste JSON-LD or the full HTML source code with embedded schema.
4. Check the detected schema types and element counts.
5. Review issues and warnings. Fix empty fields and missing properties.
6. Copy the resulting data to your deployment documentation or for change verification.

You can also compare the result with rich results tools, to make sure of the presentation.

Case study

A service website lost visibility on local queries after a template change.

Analysis showed the implemented LocalBusiness type had empty fields and missing key properties.

After filling in missing data and removing duplicates, warnings dropped to zero within a day. In the following weeks, ranking stability improved in search results.

FAQ

• Can I paste the entire HTML code of a page, not just JSON-LD?

  Yes. You can paste the full HTML source code. The tool will extract JSON-LD blocks and check them.

• What does the information about detected schema types mean?

  It’s a list of schema.org types found in the structured data. It helps assess completeness of the implementation.

• Why are there warnings about empty fields?

  Empty values in JSON-LD are usually not helpful. It’s best to fill them in or remove them depending on the type.

• Does the tool indicate what doesn’t comply with schema.org recommendations?

  Yes. You’ll get messages about common problems and missing items, in line with the schema.org approach.

• Why is competitor schema analysis useful?

  You can check what schema types the top 10 sites have and decide if it’s worth implementing them for yourself.