VASTlint

vastlint validates VAST XML ad tags directly in your browser — no copy-pasting into external tools. When you open a VAST XML URL, vastlint automatically: • Highlights every error, warning, and info issue inline on the correct line • Draws squiggly underlines under the offending XML element • Shows the rule ID and severity inline with the code • Displays the full error message and spec reference on hover • Links every rule to vastlint.org/docs for detailed fix guidance Supports VAST 2.0, 3.0, 4.0, 4.1, and 4.2. Built on vastlint — a fast, spec-accurate VAST validator written in Rust and compiled to WebAssembly. All validation runs locally in your browser. No data is sent to any server. Open source: github.com/aleksUIX/vastlint