Free developer tool

Schema Markup Tester

Validate JSON-LD syntax, inspect schema types and catch common structured-data mistakes before publishing.

Free Local code workflow Mobile friendly

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Tool guide

What is the Schema Markup Tester?

The Schema Markup Tester is a free browser-based developer utility designed for quick front-end work without installing a desktop application.

Validate JSON-LD syntax, inspect schema types and catch common structured-data mistakes before publishing. Your code stays in the current browser for the normal workflow, which makes the tool useful for experiments, learning, debugging and small production checks.

What it helps with

Key features

JSON syntax validation

Detects @context and @type

Supports object or graph markup

Readable validation messages

Formats valid JSON-LD

Step by step

How to use this tool

1
Add your code
Paste or edit the HTML, CSS, JavaScript or settings shown in the workspace.
2
Run or analyze
Use the main action to refresh the preview, generate output or inspect the code.
3
Review the result
Check the live preview, generated CSS, validation findings, console output or score cards.
4
Copy or export
Copy the useful result or download the generated file when the tool offers export.

Practical advice

Developer tips

Test important layouts at more than one viewport width before publishing.
Treat automated warnings as a fast review aid rather than a substitute for browser and assistive-technology testing.
Keep a copy of production code before minifying or applying broad automated changes.
Validate behavior in the browsers your real visitors use when compatibility matters.

Scope

What this tool does not replace

Automated front-end checks cannot reproduce every browser, device, assistive technology, network condition or production build pipeline. Use the result as a fast review layer and verify important releases in your real environment.

Common questions