HTML Validator: Check HTML Markup for Common Issues
The HTML Validator parses your HTML and checks for common accessibility and quality issues, including duplicate IDs, images without alt attributes, anchors without href attributes, and inline event handlers. Paste your markup and run a check to review the results. If the parser reports an error position, you can use it to locate the issue in your input.
The HTML Validator is a browser-based tool for checking HTML markup for common quality and accessibility issues. It parses your HTML and looks for duplicate IDs, images without alt attributes, anchors without href attributes, and inline event handlers. Use it to review a snippet or markup you are preparing to pass to another tool.
To get started, paste or drop your HTML into the input and run the check. The validator reports the supported issues it finds, and it can show an error position if there is one. That position gives you a place to inspect the input; the checks also help highlight specific markup concerns such as repeated IDs or missing attributes.
HTML uses elements and attributes to describe page content and structure. Checking markup can help you catch issues before you use it elsewhere, especially when reviewing generated HTML or checking accessibility-related attributes. This tool focuses on the checks listed above, so its results are useful for those concerns without implying that every possible HTML issue is covered.
The HTML Validator runs entirely in your browser. Your input is processed on your device and is not uploaded, stored, or sent to a server. Once the page has loaded, the tool works offline, so you can check HTML without an active internet connection.
Developers and DevOps engineers can use the validator for a quick review during editing, before passing markup into another parser, or when checking output from another tool. It offers a straightforward way to inspect common HTML issues directly in the browser.
Step 1: Paste or drop your HTML into the tool. Include the markup you want to check.
Step 2: Run the HTML check. The tool parses your input and looks for the supported accessibility and quality issues.
Step 3: Review the results for duplicate IDs, images without alt attributes, anchors without href attributes, and inline event handlers.
Step 4: If a parser error position is reported, use it to find the location in your HTML and inspect the surrounding markup.
Use case: Check HTML before passing it to another parser or runtime, and catch common markup issues early.
Use case: Use a reported parser error position to find where to inspect your HTML instead of searching the whole file by hand.
Use case: Review HTML generated by another tool for duplicate IDs and other issues the validator checks.
Use case: Check images for missing alt attributes while reviewing a page's accessibility.
Use case: Find anchors without href attributes before sharing or publishing a page.
Use case: Review markup for inline event handlers as part of a quality check.
Use case: Run a quick browser-based check on a snippet while editing HTML, without uploading the input to a server.