Ad Verification Tags

How blocking tags cause impression discrepancies

Ad verification vendors like IAS (Integral Ad Science) and DoubleVerify can operate in two modes. In monitoring mode, the tag observes and reports but does not interfere with ad delivery. Both your ad server and the advertiser's system count the impression. In blocking mode, the tag prevents the ad from rendering when it detects a brand safety issue, a keyword match, or a flagged domain. Your ad server still counts an impression, but the advertiser's system does not. The result: you served the ad, you will not get paid for it, and the reconciliation dispute happens weeks later.

Why publishers need visibility

• Blocking tags can produce 15-40% impression discrepancies on affected campaigns
• Publishers get blamed for under-delivery even though the creative's own verification tag caused it
• Blocking tags can misfire: domains wrongly blacklisted, third-party tags triggering on unrelated content, Chrome security updates breaking wrapped ads
• Many publishers have a "monitoring only, no blocking" policy but cannot enforce it without pre-flight testing
• Even monitoring tags need visibility for vendor management and data governance

How Advalidation detects verification tags

Advalidation automatically identifies IAS and DoubleVerify verification tags in both display and video creatives during QA scanning.

For display creatives, the system analyzes tag code for known wrapper patterns and inspects outbound network connections during creative execution. For VAST video creatives, it parses VAST XML for verification extensions and analyzes wrapper URLs.

Detection distinguishes between blocking and monitoring by examining vendor-specific indicators: URL patterns, configuration parameters in VAST AdParameters, and JavaScript library references. The result tells you exactly which vendor is present and what mode it is operating in.

Configuring your verification tag policy

Set your ad specification to match your publisher or broadcaster policy:

• Allow both: Accept monitoring and blocking tags (no restrictions)
• Monitoring only: Allow verification tags, fail if blocking is enabled
• No verification tags: Flag any third-party verification presence (strictest mode)

Results show the detected vendor, whether the tag is set to block or monitor, and a pass or fail verdict against your policy.

Beyond pre-launch detection

Pre-flight testing catches verification tags at campaign launch. But verification configurations can change mid-flight. A tag that was set to monitor at launch can be switched to blocking without notice. Use Campaign Monitoring to detect these changes automatically throughout the campaign lifecycle. For broader visibility into all third-party connections a creative makes, see Connection Screening.

Prevent discrepancies before they start

Stop finding out about blocking tags at reconciliation. Get in touch to see how verification tag detection fits into your pre-launch QA process.