Understanding Prebid.js First Party Data Validation: What Publishers Need to Know

First party data is now central to publisher monetization strategies, but ensuring this data is structured correctly is often overlooked. Mistakes or inconsistencies in data fields can silently cause bid losses, auction failures, or result in inaccurate targeting.

Prebid.js’s First Party Data Validation module helps publishers proactively catch and correct these issues before they impact revenue. For ad operations and revenue teams, understanding what this module does—and how to use it smartly—can make the difference between a healthy auction and missed opportunities.

What the Prebid.js First Party Data Validation Module Does

The First Party Data Validation module automatically checks the structure and data types of fields used in Prebid.js’s first party data (FPD) objects. It runs these checks at the start of each auction, looking for errors that can break compatibility with buyers or cause data to be ignored.

Common Fields and Validation Rules

Key fields such as ortb2.site.sectioncat (should be an array of strings) or ortb2.device.w (must be a number) are validated for type correctness. If a field fails its check, Prebid.js will strip it out before the auction begins—preventing malformed data from derailing the process.

For example, if a publisher mistakenly sets site.pagecat as a string instead of an array, the module will remove that field. Likewise, if device dimensions are passed as strings instead of numbers, they’re cleaned up automatically.

Handling User Opt-Outs

The module also checks for the presence of a privacy opt-out signal (such as the _pubcid_optout cookie). If detected, it removes certain user fields, such as ortb2.user.yob and ortb2.user.gender, to respect user privacy choices.

How to Implement and Control the Module

By default, this module isn’t included in every Prebid.js build to keep the JavaScript bundle lean. Publishers must explicitly add it when building their custom Prebid.js package. Once enabled, it runs validations automatically unless specifically configured to skip them.

Adding the Module to Your Prebid Build

Publishers can include the First Party Data Validation module with:

gulp build –modules=validationFpdModule

This adds about 1KB to your Prebid.js file.

Disabling or Skipping Validations

Some publishers may want to limit when these checks run, such as only during QA or major upgrades. You can skip validations at runtime using setConfig:

pbjs.setConfig({
firstPartyData: {
skipValidations: true
}
});

When skipValidations is true, Prebid.js won’t validate or strip fields.

Practical Impact on Auction Quality and Revenue

Accurate FPD improves buyer trust and targeting, while malformed data can undercut auctions. This module acts as a safeguard, catching silent errors that otherwise go unnoticed during live monetization.

Examples of Preventing Costly Failures

– If a publisher accidentally adds ortb2.imp directly under first-party data (instead of under ad units), the module will remove it, preventing auction errors.
– Fields like site.keywords, if passed as an array instead of a comma-separated string, would be removed—ensuring buyer-side expectations are met.

These small checks preserve auction integrity and prevent revenue loss from data compatibility problems.

What this means for publishers

Publishers running sophisticated header bidding need to keep data quality high to maintain auction performance. The FPD validation module minimizes risk by removing broken or mis-typed fields before they hit the auction, which means fewer hours spent troubleshooting why bids are missing or CPMs are low. For teams iterating on data strategies or deploying updates, this safety net is especially valuable.

Practical takeaway

Integrate the First Party Data Validation module during major changes to your Prebid.js setup—especially when adding or modifying FPD fields. Use it as a QA aid before pushing updates live, even if you ultimately disable validations in production for bundle-size reasons.

Regularly verify that your FPD structure matches buyer and Prebid.js expectations. Use this module to catch silent mistakes that could otherwise go unnoticed but have real revenue impacts. Building these checks into your workflow keeps your auctions clean, minimizes troubleshooting, and supports higher, more reliable yield.