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VAST Tester Online – Free VAST Tag Validation Tool

Inspect and validate VAST ad tags online to ensure compliance with IAB standards and optimal video advertising performance.

Enter Your VAST Tag URL for Testing

How to test a VAST URL

VAST Tag Examples

How Our VAST Tester Online Works

  • Paste your VAST tag URL into the input field.
  • Click the "Validate" button to start the validation process.
  • Review the validation results and fix any issues using the provided feedback.

What is a VAST Tester?

A VAST tester is a tool that loads your VAST XML ad tag and simulates how a video player would interpret it. Instead of guessing whether your tags will deliver correctly, you can test them online and spot issues before launch.

VAST Video Ad Preview and Inspector

How the Video Preview Works

VAST Tag Preview & Validation

Once you paste your VAST tag URL and click Validate, your VAST tag preview will appear here. Our VAST tester online instantly loads your ad response, showing a live video ad playback, media file details, and tracking events.

Our 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

By running your tags through the preview, you can be confident your video ads will deliver correctly before launching campaigns.

VAST Validation Results

Common VAST Errors Our Tester Detects

  • Invalid XML formatting
  • Missing media files or creative elements
  • Tracking events not firing
  • Timeout or no ad response
  • Wrapper chain errors
Common VAST Errors

Results example

After you validate your VAST tag, you'll see a detailed breakdown of each section of your VAST XML. The results show which parts passed, which failed, and how to fix any issues found.

Passed example:
- AdSystem, AdTitle, Impression
Failed example:
- MediaFile (missing or invalid URL)
Warning or Optional example:
- Companion Ads (optional)
Tip: Click on each result for more details and suggestions on how to fix any issues that may have been detected.
Visit our help center for more information:
Help Center docs on VAST Tag Validation Results

Always review your VAST tags in multiple VAST testers to ensure compatibility.

Helpful VAST guides.

Try our new VAST tag generator playground to generate and test VAST tags examples.

Get help on generating VAST tags
VAST XML Examples & Fundamentals: Events, Video Clicks, and Media Files
VAST XML

VAST XML Examples & Fundamentals: Events, Video Clicks, and Media Files

Explore the anatomy of a VAST tag, learn how event tracking and Video clicks work, and see how media files differ across web, mobile apps, and CTV with real VAST XML examples.

Read insight

Frequently Asked Questions

What is a VAST tester?

A VAST tester is a tool that lets you simulate how a video player would process your VAST XML ad tag, helping you validate creatives, tracking, and delivery.

How can I test interactive video ads?

You can test interactive video ads using our video ad tester, which simulates the ad playback environment to ensure your interactive video creatives function correctly. Interactive video ads are often VPAID, SIMID and SHARC formats.

What is video ad pod?

A video ad pod is a group of video ads or a collection of ads that are played sequentially within a single ad break. This allows for multiple ads to be shown to the viewer in a single viewing session. Pods are generally scheduled to play at the beginning (pre-roll), in the middle (mid-roll), or at the end (post-roll) of the content.

How can I test a multi-VAST tag or VMAP tags?

You can test a multi-VAST tag or VMAP tags by using our VAST tester, which supports both formats and provides detailed validation results.

How do I test a VAST tag online?

Simply paste your VAST tag URL into our VAST tester online, and it will load the ad response, show the video playback, and report any issues.

What errors can a VAST tester detect?

Our tester checks for XML validation issues, missing creatives, wrapper problems, tracking errors, and more.

Is this VAST tester free?

Yes, our VAST tester is completely free to use.