Meta vs Postback Conversions — Which to Trust
Last updated: April 18, 2026
Wevion tracks conversions from two different sources: Meta's reported conversions and postback (server-to-server) conversions. Understanding the difference — and knowing which to trust — is critical for making accurate optimization decisions.
Prerequisites
- Campaigns running with conversion tracking set up.
- Familiarity with basic conversion concepts.
CPA, CPM, CTR — Core Metrics Decoded
How It Works
Meta Conversions (Pixel/CAPI)
Meta tracks conversions using its Pixel (browser-based) and Conversions API (CAPI) (server-based). These conversions are attributed using Meta's attribution model, which typically uses a 7-day click / 1-day view window. This means:
- If someone clicks your ad and converts within 7 days, Meta claims that conversion.
- If someone views your ad (without clicking) and converts within 1 day, Meta claims that conversion.
Meta's numbers appear in the standard campaign metrics as conversions and purchase_value.
Postback Conversions (Server-to-Server)
Postback conversions come from your tracking system (e.g., your affiliate network, CRM, or tracking platform) sending conversion data directly to Wevion's server. These are tracked using click IDs or sub IDs embedded in your ad URLs, providing a direct 1:1 mapping between a click and a conversion.
In Wevion, postback conversions appear as separate fields — pb_conversions and pb_revenue — and are used to calculate the ROI displayed on your Dashboard.
Why They Differ
| Factor | Meta Conversions | Postback Conversions |
|---|---|---|
| Attribution | Uses Meta's model (7d click / 1d view) | Direct click-to-conversion mapping |
| View-through | Included (1-day view window) | Not included (click-only) |
| Cross-device | Meta tracks across devices via login | Only tracks the click device/session |
| Deduplication | May double-count across campaigns | One conversion = one postback |
| Delay | Can take up to 72 hours to fully attribute | Real-time (arrives when conversion happens) |
| iOS impact | Affected by ATT/SKAdNetwork limitations | Not affected (server-to-server) |
Step-by-Step Guide
1. View Both Numbers Side by Side
In the Ads Manager, your campaign table shows both Meta-reported conversions and postback conversions (if configured). Compare these two columns:
- Conversions (Meta) — what Meta reports via Pixel/CAPI
- PB Conversions — what your tracking system reports
2. Calculate the Discrepancy
A common formula:
Discrepancy % = ((Meta Conversions − Postback Conversions) / Postback Conversions) × 100
- 0–20% discrepancy: Normal range. Meta typically reports higher due to view-through attribution.
- 20–50% discrepancy: Worth investigating. Check your tracking setup for missed conversions.
- 50%+ discrepancy: Something is likely broken — your pixel, CAPI integration, or postback URLs need attention.
3. Decide Which to Use for Optimization
For budget decisions (scaling/pausing), use postback conversions. They are:
- More conservative (no view-through inflation)
- Real-time (no attribution delay)
- Not affected by iOS privacy changes
- Directly tied to your actual business outcomes
For audience learning and campaign optimization within Meta, use Meta conversions. They:
- Feed Meta's algorithm for optimization
- Include cross-device attribution
- Provide richer signals for the delivery system
4. Understand Dashboard vs. Ads Manager
Wevion's Dashboard calculates ROI using postback data:
ROI = (Postback Revenue − Spend) / Spend × 100
This gives you a conservative, "real money" view of your return. The Ads Manager shows both sources so you can compare.
Options and Configuration
Setting Up Postback Tracking
Postback conversions require a server-to-server integration between your tracking platform and Wevion. This is typically configured in your tracking platform by adding Wevion's postback URL with the appropriate parameters (click ID, revenue, etc.).
Postback Conversions — Server-to-Server Tracking
Time Alignment
Meta conversions may be attributed to the click date (not the conversion date), while postbacks are typically timestamped at the conversion time. This can cause daily numbers to differ even when the totals over a longer period align.
When comparing, use a 7+ day window to smooth out attribution timing differences.
FAQ
Q: Meta shows 50 conversions but I only have 30 postbacks. Which is correct? A: Both are "correct" from their respective perspectives. Meta's number includes view-through conversions and cross-device attribution. Your postback number reflects only direct, server-confirmed conversions. For profitability decisions, trust the postback number. For understanding Meta's delivery optimization, the Meta number is relevant.
Q: My postback conversions are higher than Meta's. Is that possible? A: Yes, in some cases:
- Organic conversions (not from ads) might trigger a postback if the tracking isn't perfectly isolated.
- Duplicate postbacks from retry logic in your tracking system.
- Attribution window mismatches (postback counts a conversion Meta doesn't attribute).
Review your tracking setup to ensure postbacks are correctly tied to ad clicks only.
Q: Should I set up rules based on Meta conversions or postback conversions? A: Wevion's rules engine uses Meta-reported metrics (purchases, purchase_value, conversions) for condition evaluation, as this data is available at the campaign/adset/ad level with full granularity. Use these for automation, but cross-reference with postback data for overall profitability decisions.
Q: How does iOS privacy (ATT) affect this? A: iOS App Tracking Transparency significantly impacts Meta's pixel-based tracking, leading to underreported conversions on Meta's side. CAPI and postback tracking are less affected because they don't rely on browser cookies. This is another reason to prioritize postback data for business decisions.