Why CAPI Setup Guides Leave Out the Hard Part#

You installed the Facebook Conversions API plugin. Events are firing. But your Event Match Quality score sits at 4 or 5—and every guide told you this would fix your attribution. The problem isn’t your installation. It’s that basic CAPI plugins send the event without the customer data Meta needs to match it to real users.

Here’s what EMQ actually measures, why most WooCommerce plugins max out at mediocre scores, and what data enrichment really means for your Facebook ad performance.

What Event Match Quality Actually Measures#

Event Match Quality (EMQ) is Meta’s score from 0-10 that reflects how accurately your conversion events match to real Facebook users. A good EMQ score in 2025 is 6 or higher, with 8+ being optimal for ad performance, according to CustomerLabs research.

When you fire a Purchase event through CAPI, Meta tries to connect that event to a specific person in their database. They do this using customer identifiers—hashed email, phone number, first name, last name, external ID, and click IDs like fbp and fbc.

The more identifiers you send, the more confident Meta becomes about the match. One identifier (just an email) gives Meta limited options. Multiple identifiers (email + phone + external ID + click ID) create a clear picture that Meta can match reliably.

Why Basic Plugins Max Out at 5-6#

Most WooCommerce CAPI plugins send the event itself correctly. Your Purchase fires when the order completes. ViewContent fires on product pages. Server-side delivery bypasses ad blockers. So why the low EMQ?

Basic plugins send minimal customer data with each event. They might include a hashed email—but skip phone number, first name, last name, and external ID. Some don’t properly capture the fbp and fbc cookies that link the conversion back to the ad click.

Here’s the hierarchy Meta uses to match events, ranked by priority:

• External ID (your customer ID) – High priority
• Email address (SHA256 hashed) – High priority
• Phone number (SHA256 hashed, with country code) – High priority
• Click ID (fbc) – Links directly to ad interaction
• Browser ID (fbp) – Links to browser session
• First name + Last name – Supporting identifiers
• City, State, Country, Zip – Additional context

Higher-funnel events (ViewContent, AddToCart) will naturally score lower—usually 3-5—because visitors haven’t entered any personal information yet. That’s expected. But Purchase events should score 7-10 since you have full customer details at checkout.

The Data Enrichment Gap#

Data enrichment means sending more customer parameters with your events. It’s the difference between:

Basic plugin sends:

• Event name: Purchase
• Value: $127.50
• Email: [hashed]

Enriched data sends:

• Event name: Purchase
• Value: $127.50
• Email: [hashed]
• Phone: [hashed with country code]
• First name: [hashed]
• Last name: [hashed]
• External ID: customer_12345
• City, State, Zip: [hashed]
• fbc: click ID from URL
• fbp: browser ID from cookie

That second payload gives Meta everything it needs for confident matching. The first leaves Meta guessing.

Why This Matters for Your Ad Spend#

Low EMQ doesn’t just mean bad reports. It actively hurts your campaign performance:

Attribution becomes unreliable. Meta can’t accurately credit which ads drove conversions. You’re making optimization decisions with incomplete data.

Campaigns stay stuck in learning phase. Meta’s algorithm needs confident conversion signals to exit learning efficiently. Low EMQ extends learning periods and increases costs.

Retargeting audiences shrink. Custom audiences based on website events miss the users Meta couldn’t match. Your retargeting pool is smaller than your actual customer base.

Lookalike quality suffers. Lookalikes built on incomplete seed audiences perform worse. You’re scaling with a distorted picture of your best customers.

The iOS 14.5+ Compounding Effect#

Apple’s App Tracking Transparency made EMQ even more critical. When users opt out of tracking (most do), Meta has fewer signals to work with. Your first-party data—the customer identifiers you send—becomes the primary matching mechanism.

With iOS restrictions blocking device-level tracking, Meta relies almost entirely on the hashed customer parameters you provide through CAPI. High EMQ was always important; now it’s essential.

How to Check Your EMQ Score#

In Facebook Events Manager:

1. Navigate to Events Manager in Business Suite
2. Select your pixel from Data Sources
3. Click on individual events (like Purchase)
4. Look for the Event Match Quality column showing your score out of 10
5. Click the score for detailed breakdown of which parameters are present or missing

Meta shows exactly which identifiers are being received and which are missing. This diagnostic tells you precisely what data your current setup isn’t sending.

What High EMQ Implementation Requires#

Getting EMQ above 7 requires capturing and transmitting more customer data. This means:

Proper SHA256 hashing. All customer identifiers must be hashed before sending. The hashing must follow Meta’s specifications—lowercase, trimmed, formatted correctly.

Phone number formatting. Phone numbers need country codes included before hashing. US number 555-123-4567 becomes +15551234567 then gets hashed.

Cookie capture. The fbp (Facebook Pixel browser ID) and fbc (click ID from ad URL) cookies need to be captured and included with server events for deduplication and click attribution.

External ID consistency. Your WooCommerce customer ID should be sent consistently across events so Meta can track the same person through their journey.

The Transmute Engine Approach#

The Transmute Engine™ captures all available customer parameters at the WooCommerce level and sends them properly formatted to Meta CAPI. Email, phone, name, address, external ID, and click cookies—all hashed correctly, all included with every eligible event.

For checkout and purchase events where customer data is available, enriched payloads push EMQ scores into the 8-10 range. Combined with coded UTM parameter tracking, you maintain attribution even when ad blockers hide browser-side data.

No manual configuration of data layer variables. No GTM server containers to manage. Just complete customer data flowing to Meta through server-side connections.

Key Takeaways#

• EMQ scores below 6 indicate incomplete customer data—not CAPI installation problems
• Basic plugins send events but skip data enrichment—email alone isn’t enough for confident matching
• Purchase events should score 7-10 since you have full customer details at checkout
• Higher-funnel events (ViewContent, AddToCart) naturally score 3-5—that’s expected for anonymous visitors
• iOS privacy changes make first-party data essential—CAPI customer parameters are now primary matching signals
• Low EMQ hurts attribution, learning phase, retargeting, and lookalike audiences—it’s not just a reporting problem

Ready to push your EMQ above 8? See how Transmute Engine handles data enrichment.