Overview
This validator is built for markup review, not styling. It inspects the HTML tree for unsafe elements, repeated IDs, invalid nesting, empty links, missing alt text, and other structural problems that often slip into templates and pasted content. Use it when you need to confirm that a snippet can be published safely or embedded without breaking scripts, anchors, or accessibility. The report helps you separate hard errors from warnings so you can fix the problems that matter first.
Use cases
- Template review before releaseInspect landing page and article templates for invalid nesting, missing attributes, and repeated IDs before they go live.
- CMS paste auditReview content copied from editors or legacy systems for unsafe tags, broken links, and messy markup.
- Accessibility issue huntingFind duplicate IDs, empty anchors, and images without alt text that can confuse assistive technology.
- Email or page-builder cleanupCheck HTML exported from builders or email editors for unsupported elements and malformed structure.
- Script-safe embed checkVerify that a widget or snippet does not include tags or attributes that can interfere with the host page.
How it works
- 1
Paste your HTML into the input field.
- 2
Run the check to inspect tags, attributes, nesting, and IDs.
- 3
Review errors and warnings in the report.
- 4
Edit the HTML and check it again until the output is clean.
Examples
Duplicate ID report
Input: <section id="promo"><a id="cta" href="/start">Start</a><button id="cta">Go</button></section>
Output: Flags the repeated id="cta" and highlights the elements involved.
Useful when the same identifier is reused across interactive elements.
Unsafe tag detection
Input: <div class="note">Hi</div><script>track()</script>
Output: Marks the script tag as unsafe markup for published content.
Shows how the validator treats code that should be removed before publishing.
Nesting and attribute check
Input: <p><div>Broken</div></p><img src="cover.jpg">
Output: Reports invalid nesting and missing alt text on the image.
Helps catch structural problems that are easy to miss in copied HTML.
FAQ
Will the validator rewrite my HTML?
No. It only analyzes the input and returns findings such as errors, warnings, and structural notes.
What counts as unsafe markup here?
Tags and patterns that are risky in published content, such as script-like embeds or other elements the validator marks as unsafe.
Why is a duplicate ID a problem?
IDs must be unique. If two elements share the same ID, fragment links, scripts, and accessibility relationships can point to the wrong node.
Do empty links and missing alt text matter?
Yes. Empty anchors and images without meaningful alt text are reported because they weaken the document structure and usability.
Why does valid-looking HTML sometimes still get warnings?
A snippet can be syntactically acceptable but still contain issues like repeated IDs, empty attributes, or unsupported elements that the validator flags.