VAST Tag Validator
Use this tool to validate your VAST tags by entering a VAST tag URL or VAST XML content. The validator will analyze the structure of your VAST XML, check for common errors, and provide insights to help you debug any issues.
Other Ad Validators
VAST Tester & Validator – VAST Player to Validate and Preview VAST Ads
Validate and preview your VAST ad tags online. Our free VAST tester simulates a video ad preview, detects XML errors with advanced VAST QA tools to ensure IAB-compliant and delivery
Enter VAST Tag URL
Accepts VAST Tag URLs and VAST XML
VAST Tag Preview & Validator
Once you paste your VAST tag URL or XML and click Preview, your VAST tag preview will appear here. Our VAST online validator instantly loads your ad response, showing a live video ad playback, media file details, and tracking events.
Video ad previews are powered by the Google IMA SDK.
Our VAST tester helps you
- Debug and troubleshoot VAST errors
- Preview video ads in real-time
- Inspect media assets and tracking pixels
- Verify compliance with VAST standards
- How to fix common VAST errors detected during validation
Go beyond basic Ad previews
Create a free account to access advanced test features and save your test history
Ad Info
Events LogRealtime events0
VAST Validation Results
What We Test For?
When you run a test in our VAST Tag Tester, we check your VAST or VMAP tag for the following common issues and best practices
to view the full VAST Tag test analysis
VAST Version
Checks if the VAST version is supported and valid.We currently support all versions of VAST: 2.0, 3.0, 4.0, 4.1, 4.2
Why we test this:
Different VAST versions introduce new elements and deprecate old ones. Testing ensures the XML structure and features align with the supported version, preventing compatibility issues with players and ad servers.
Media Files
Ensures media files are present and properly formatted.We support various media file types including MP4, WebM, and Ogg.
Why we test this:
Media files are the core of any video ad. Testing ensures the file type, codec, bitrate, and delivery method meet player compatibility standards, preventing playback errors and poor viewing experiences.
Ad Duration
Validates that the ad duration is specified and reasonable.We recommend a duration of 15–30 seconds for most ads.
Why we test this:
A defined duration helps players allocate correct playback time and manage ad pods efficiently. Missing or invalid durations can cause playback interruptions or failed ad requests.
Tracking Events
Checks for required tracking events and their correctness.We support various tracking events including start, firstQuartile, midpoint, and complete.
Why we test this:
Tracking events provide essential performance metrics such as completion rate and viewer engagement. Missing or incorrect events lead to inaccurate analytics and reporting discrepancies.
Click Tracking
Verifies click tracking URLs are present.Click tracking is essential for measuring ad engagement.
Why we test this:
Click tracking URLs record user interactions with the ad. Without proper click tracking, advertisers lose insight into engagement and campaign effectiveness, affecting billing and performance analysis.
Impression Tracking
Ensures impression tracking is implemented.Impression tracking helps monitor ad views and performance.
Why we test this:
Impression tracking confirms when an ad has been served and viewed. It’s a critical metric for verifying delivery, preventing fraud, and ensuring accurate reporting to advertisers and publishers.
Companion Ads
Checks for valid companion ads if present.Companion ads enhance user engagement alongside video ads.
Why we test this:
Companion ads extend the ad experience across formats and screens. Testing ensures they are correctly linked and formatted, avoiding display issues and maintaining creative consistency.
Ad System
Validates the AdSystem element.AdSystem identifies the ad server or system that provided the ad.
Why we test this:
The AdSystem element provides transparency about the ad’s origin and helps with troubleshooting, analytics, and attribution across ad delivery chains.
API Framework
Checks for correct API framework usage.Common API frameworks include VPAID and SIMID.
Why we test this:
The API framework defines how the creative interacts with the player. Testing ensures compatibility with supported frameworks, avoiding execution failures or blocked interactions on CTV and desktop environments.
Ad Sequence
Validates ad pod sequence numbers (for sequential ads).Ensures ad sequence numbers are unique and properly ordered.
Why we test this:
Ad sequence testing guarantees that ads play in the intended order within a pod, ensuring storytelling, pacing, and compliance with campaign delivery requirements.
Sequence Timing
Checks total duration and timing of ad pods.Ensures total ad pod duration is within acceptable limits.
Why we test this:
Proper sequence timing maintains a smooth viewing experience. Overly long or poorly timed ad pods can cause user drop-off, violate publisher limits, or fail ad insertion rules.
VMAP Version
Checks VMAP version (for VMAP tags).We currently support VMAP 1.0.
Why we test this:
VMAP defines how ad breaks are scheduled in long-form content. Testing ensures compliance with supported VMAP standards, preventing scheduling conflicts or playback errors in ad stitching systems.
Ad Breaks
Validates ad breaks in VMAP.Ensures ad breaks are properly defined and formatted.
Why we test this:
Ad breaks determine when and how ads appear during content playback. Validating them ensures correct structure, preventing missing mid-rolls or misaligned ad placements.
Ad Break Timing
Checks timing of ad breaks in VMAP.Ad breaks should be scheduled at appropriate intervals.
Why we test this:
Properly timed ad breaks maintain viewer engagement and balance monetization with user experience. Poorly spaced breaks can lead to audience frustration or reduced ad revenue.
VAST References
Ensures VMAP ad breaks reference valid VAST tags.We currently support VAST 2.0, 3.0, and 4.0+
Why we test this:
Each ad break in a VMAP should point to a valid VAST tag. Testing ensures referenced VAST URLs are accessible and well-formed, avoiding empty breaks or failed ad requests during playback.
Why preview and Validate Your VAST Ads?
Validating VAST tags can be a critical step in ensuring video ads deliver correctly across platforms, devices, and supply-side environments. A VAST tag is essentially the instruction set that tells a video player how to load, render, track, and measure an ad. If even one part of that instruction set is incorrect or unsupported, the ad may fail to play, track inaccurately, or be rejected entirely by publishers or DSPs when trafficing. Validating VAST tags early helps catch errors before they impact revenue, campaign performance, or user experience.
From a performance and measurement standpoint, VAST validation ensures that tracking events, impressions, quartiles, clicks, and errors are firing as expected. Misconfigured macros, missing events, or invalid XML structures can lead to under-reporting, billing disputes, and optimisation decisions based on incomplete data. By validating a VAST tag, advertisers and ad operations teams can confirm that the tag adheres to the VAST specification, resolves redirects correctly, and behaves consistently across different video players and environments such as OLV, CTV, OTT, and web.
VAST validation reduces risk and can speeds up campaign launches. Many publishers, SSPs, and platforms will automatically reject tags that fail basic validation checks, delaying go-live timelines and increasing back-and-forth between teams. Proactive validation allows issues to be fixed upstream, improving approval rates and confidence that the ad will render correctly in real-world conditions. In short, VAST tag validation is not just a technical best practice - it’s a foundational step for reliable video advertising at scale.