Vastlint brings inline VAST ad tag linting to VS Code and forks
aleksuix built Vastlint, a VS Code extension that lints VAST XML video ad tags inline as you type, covering 108 rules across the full IAB VAST spec from versions 2.0 to 4.3, with validation running locally via WASM.
Score breakdown
Ad tech developers working with VAST XML can now catch spec violations at authoring time inside their existing AI-assisted editors (Cursor, Kiro, Windsurf) instead of discovering broken tags in QA or after a campaign runs.
- 01Vastlint is a VS Code extension for inline linting of VAST XML video ad tags, built by aleksuix.
- 02VAST XML is a ~20-year-old, 200-page-spec format used to deliver video ads on the web and TV.
- 03The extension implements 108 rules covering the IAB VAST spec from versions 2.0 to 4.3.
aleksuix built Vastlint out of frustration with debugging VAST XML issues after the fact. VAST XML is the 20-year-old, 200-page-spec format used to deliver video ads on the web and TV, and broken tags are described as incredibly common — typically caught only in QA or post-campaign rather than at authoring time. The author notes the US video ad market is around $30B per year, with a significant portion lost to errors they consider preventable.
The extension provides three feedback surfaces: inline squiggles on offending tags as you type, hover tooltips describing what is wrong and how to fix it, and a Problems panel showing file and line number.
The extension provides three feedback surfaces: inline squiggles on offending tags as you type, hover tooltips describing what is wrong and how to fix it, and a Problems panel showing file and line number. It covers 108 rules spanning the full IAB VAST spec from version 2.0 to 4.3. Validation runs locally via WASM, meaning no network calls are made. The extension is published on both the VS Code Marketplace and Open VSX, giving it compatibility with VS Code, Cursor, Windsurf, Kiro, VSCodium, Gitpod, and Theia.
Key facts
- 01Vastlint is a VS Code extension for inline linting of VAST XML video ad tags, built by aleksuix.
- 02VAST XML is a ~20-year-old, 200-page-spec format used to deliver video ads on the web and TV.
- 03The extension implements 108 rules covering the IAB VAST spec from versions 2.0 to 4.3.
- 04Feedback surfaces include inline squiggles, hover tooltips with fix guidance, and a Problems panel with file and line numbers.
- 05Validation runs entirely locally via WASM — no network calls.
- 06Available on both the VS Code Marketplace and Open VSX, supporting VS Code, Cursor, Windsurf, Kiro, VSCodium, Gitpod, and Theia.
- 07The US video ad market is described as around $30B per year, with many errors currently caught only in QA or post-campaign.