EmEditor featuresSyntax Checker which validates HTML, CSS, JSON, and XML files. Syntax Checker usesCSS HTML Validator Lite. If there is a syntax error or warning in your document, a window appears next to your document describing where and what the issue is. The invalid syntax is also highlighted in the document.

CSV documents are also checked, and it raises an error if an inconsistent number of columns in each line is detected. You can fix the inconsistent number of columns withCSV > Advanced > Make Number of Columns Same.