What Is Meta Conversions API (CAPI)? Server-Side Tracking for Facebook and Instagram Ads

Meta Conversions API (CAPI) is a server-side event tracking interface that lets you send conversion data directly from your server to Meta’s ad platform. Unlike the Meta Pixel (which runs in the user’s browser), CAPI operates independently of cookies, ad blockers, and browser restrictions.

For The Upload Offline Conversions App (TUOCA), the Conversions API is the primary method for uploading offline conversions — booked jobs, completed services, and closed deals — to Facebook and Instagram Ads.

Why CAPI Exists

The Meta Pixel has fundamental limitations in today’s privacy landscape:

Limitation	Impact
Ad blockers	GWI’s April 2025 research found that about 1 in 3 internet users worldwide use an ad blocker at least sometimes (15% in North America). A blocker can stop the Pixel, so the browser never sends the event.
iOS ATT	Apple’s prompt asks the person to allow or refuse tracking across apps. Many people refuse.
Browser cookie restrictions	Safari ITP, Firefox ETP limit cookie lifetimes
Offline conversions	The Pixel can’t fire for phone calls, in-person visits, or CRM events
Server-side events	Backend processes (payment confirmations, lead qualification) can’t trigger browser JavaScript

CAPI solves all of these by moving the event transmission from the browser to the server. Your server sends events directly to Meta’s /events endpoint — no browser involvement needed.

How CAPI Works

Architecture

Traditional Pixel Flow:
  User Browser → Meta Pixel (JavaScript) → Meta Servers

CAPI Flow:
  Your Server → HTTPS POST → Meta Conversions API → Meta Servers

Combined (Recommended):
  User Browser → Meta Pixel → Meta Servers ←── Your Server → CAPI
                                    ↓
                            Deduplication via event_id

The CAPI Request

Events are sent as HTTP POST requests to Meta’s Graph API:

POST https://graph.facebook.com/v26.0/{PIXEL_ID}/events

Event Structure

{
  "data": [{
    "event_name": "Purchase",
    "event_time": 1714502400,
    "action_source": "system_generated",
    "event_id": "order_12345",
    "user_data": {
      "em": ["a8b14f04b2be6c5f..."],
      "ph": ["d4f5c3b1e72a9f8d..."],
      "fbc": "fb.1.1714000000.IwAR3x7..."
    },
    "custom_data": {
      "value": 4500.00,
      "currency": "USD"
    }
  }],
  "access_token": "YOUR_ACCESS_TOKEN"
}

Key Fields Explained

Field	Required	Purpose
event_name	Yes	What happened (Purchase, Lead, etc.)
event_time	Yes	Unix timestamp of the event
action_source	Yes	How the event was generated (system_generated for offline)
event_id	Recommended	Unique ID for deduplication with Pixel
user_data.em	Recommended	SHA-256 hashed email(s)
user_data.ph	Recommended	SHA-256 hashed phone(s)
user_data.fbc	Optional	Facebook click parameter (from FBCLID)
user_data.fbp	Optional	Facebook browser ID (from _fbp cookie)
custom_data.value	Recommended	Conversion value (revenue)
custom_data.currency	Recommended	ISO 4217 currency code

Action Sources

The action_source field tells Meta how the conversion was generated:

Value	When to Use
website	Online conversion (use with Pixel deduplication)
app	Mobile app event
phone_call	Customer called after seeing ad
chat	Customer converted via messaging
physical_store	In-person conversion
system_generated	Server-side processing (CRM, automated)
other	Catch-all

For TUOCA’s offline conversion uploads, system_generated is the standard action source, since conversions are detected and uploaded by TUOCA’s relay pipeline.

User Data Matching

CAPI’s effectiveness depends on the quality of user data you send. Meta matches events to ad clicks using these hashed identifiers:

Identifier	Field	Match Quality	Notes
Email	em	★★★★★	Highest match rates; lowercase and trim before hashing
Phone	ph	★★★★	E.164 format before hashing
Facebook click (fbc)	fbc	★★★★★	Best when available; 7-day window
Facebook browser (fbp)	fbp	★★★	From _fbp cookie
First name	fn	★★★	Lowercase before hashing
Last name	ln	★★★	Lowercase before hashing
City	ct	★★	Lowercase, no special characters
State	st	★★	2-letter code, lowercase
Zip code	zp	★★	First 5 digits (US)
Country	country	★★	ISO 2-letter, lowercase
External ID	external_id	★★★	Your CRM’s customer ID (hashed)

All PII fields must be SHA-256 hashed before sending. Use the SHA-256 Hasher tool to verify your hashing.

Deduplication

When using both Pixel and CAPI (recommended), the same event may be reported twice. Meta deduplicates using the event_id field:

1. Pixel fires with event_id: "order_12345"
2. CAPI sends the same event with event_id: "order_12345"
3. Meta recognizes the duplicate and counts it once

For offline-only conversions (TUOCA’s primary use case), deduplication isn’t an issue — there’s no Pixel event to duplicate against. However, it’s still best practice to include an event_id for idempotent retries.

CAPI Event Quality Score

Meta assigns an Event Match Quality (EMQ) score to each event, ranging from 1 (poor) to 10 (excellent). Higher scores mean better matching:

Score Range	Meaning	Typical Cause
8-10	Excellent	fbc + email + phone + name
6-7	Good	Email + phone
4-5	Fair	Email only
1-3	Poor	No identifiers matched

To check your EMQ: Meta Events Manager → Data Sources → Your Pixel → Event Match Quality.

How TUOCA Uses CAPI

TUOCA integrates directly with Meta’s Conversions API:

1. OAuth authentication — Secure connection to your Meta Business account
2. Data extraction — Pulls conversion data from your connected sources (CallRail, CRM, webhooks)
3. PII processing — Normalizes email (lowercase, trim), phone (E.164), and name (lowercase) per Meta’s rules
4. SHA-256 hashing — Hashes all PII fields before transmission
5. fbc construction — Converts raw FBCLIDs to fbc format
6. Event transmission — Sends batched events to the Conversions API
7. Deduplication — Generates consistent event_ids to prevent duplicate reporting
8. Error handling — Catches and logs CAPI-specific errors (invalid hash format, expired events, rate limits)

Getting Started with CAPI

1. Create a Meta Business account and set up a Pixel
2. Generate an access token in Events Manager → Settings → Generate Access Token
3. Enable CAPI in Events Manager → Settings → Conversions API
4. Configure TUOCA — Connect Meta as a destination, provide your Pixel ID and access token
5. Send test events — Use the Events Manager Test Events tool to verify
6. Monitor EMQ — Check your Event Match Quality score and optimize

For a complete walkthrough, see the Meta/Facebook Offline Conversions Guide.