VAST Tag Tester is a free online tool that validates VAST XML tags (2.0–4.3) for errors, tracking pixels, and IAB compliance without requiring an account.
What is VAST Tag Tester?
VAST Tag Tester is a browser-based tool that takes a VAST URL or raw XML and outputs a structured breakdown with error/warning detection, tracking pixel audit, and media file analysis. It supports VAST 2.0 through 4.3 and automatically resolves wrapper chains up to 5 hops. No server-side processing delays; parsing happens instantly.
Key Features
- Instant XML Parsing — Paste any VAST URL or raw XML and get a structured breakdown in under a second; all processing happens client-side.
- IAB Spec Compliance — Validates every attribute and element against VAST 2.0, 3.0, 4.0, 4.1, 4.2, and 4.3 schemas.
- Tracking Pixel Audit — Extracts all impression, click, and quartile tracking URLs and performs real HTTP checks to verify they resolve.
- Zero Configuration — No account, API key, or extension needed; open the page and start testing immediately.
- Wrapper Chain Resolution — Automatically follows VAST wrapper redirects up to 5 levels deep, validating each hop.
- Media File Analyzer — Lists all MediaFile elements with codec, bitrate, dimensions, and MIME type.
- Error Code Reference — Every detected VAST error links to the full IAB description and common fix recommendations.
- 100% Free & Private — No account required, tags are never stored or logged.
Who is it for?
- Publishers — Validate video ad tags before placement to prevent revenue loss from broken creatives.
- Ad ops professionals — Audit tracking pixels and wrapper chains daily to ensure billable events fire correctly.
- Programmatic advertising engineers — Test VAST 4.3 features and troubleshoot error codes during integration.
- DSPs and agencies — Verify ad server responses across multiple versions without signing up for a paid tool.
What can you do with VAST Tag Tester?
- Pre-launch validation — Test a new VAST tag from your ad server (GAM, Freewheel, etc.) to catch errors like XML parse failure (100) or trailer limit exceeded (303) before they reach viewers.
- Tracking pixel audit — Check that all impression, quartile, click, and error beacons have valid HTTP status codes and correct vendor URLs.
- Wrapper chain debugging — Follow a multi-hop wrapper chain to identify which redirect step is failing or missing required attributes.
- Media file compatibility check — Review codec, bitrate, and dimensions of all MediaFiles to ensure they match your video player's requirements.
How does VAST Tag Tester work?
- Paste a VAST tag URL or raw XML into the input field. 2. Click "Validate Tag" — the tool fetches and parses the XML, resolves wrapper chains up to 5 hops, and runs all spec checks in real time. 3. Inspect the results: errors and warnings are listed with IAB error codes, tracking pixels are extracted with HTTP status, and media files are detailed with codec/bitrate/dimensions.
Pricing
VAST Tag Tester is completely free with no tiers or sign-up required. Run unlimited tests with no account creation.
FAQ
What is a VAST tag tester?
A VAST tag tester parses and validates the XML response from your ad server against the IAB VAST specification (2.0–4.3). It detects errors in ad delivery, tracking discrepancies, and media file issues to ensure video ads work correctly before going live.
