HTML Semantic Checker
Check heading structure, image alt text, form labels, lang attributes, and semantic HTML basics.
What is an HTML semantic checker?
An HTML semantic checker reviews markup from a document-structure and basic accessibility perspective. It detects skipped h1 to h6 levels, a missing h1, html lang, title, viewport, description, or main landmark, and flags issues such as image alt, iframe title, link href, button names, and form labels. It does not rewrite your code; it shows improvement points before release.
How to use the HTML semantic checker
- Paste a complete HTML document or a page snippet and click Check HTML. Load the example to see common findings.
- Fix red issues first, such as missing h1, title, lang, image alt, or form-control names. Then review yellow suggestions for heading order, viewport, and description.
- Return to the source using each line and column position, confirm that the semantics match the page intent, and check again. Finish with a real browser and assistive technology when possible.
Main semantic checks
Heading hierarchy
Detects a missing h1, multiple h1 headings, or jumps such as h2 to h4 so the document outline is easier to understand.
Page essentials
Checks html lang, title, viewport, description, and the main landmark so search engines, browsers, and assistive technologies receive clearer page information.
Controls and media
Checks image alt, iframe title, accessible button names, and whether inputs have a label or another accessible name.
Local privacy check
Source is analyzed in the current browser without deploying the page first. Follow your security policy for confidential code and review external resources referenced by the source.
HTML semantic checker FAQ
Does the semantic checker fix source automatically?
No. It reports findings and positions without changing the original source. Semantics depend on page content and interaction intent, so a developer should confirm and edit the markup.
Why are some findings suggestions instead of errors?
Items such as heading count, description, viewport, and main can depend on the page type. An embedded snippet may not contain a complete document skeleton, so these findings are suggestions for you to evaluate in context.
Does the result prove full accessibility compliance?
No. It covers common static semantic hints and does not replace keyboard testing, screen-reader testing, color-contrast checks, dynamic-state checks, or human content review. Formal release should include a broader accessibility process and real user scenarios.
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