CentriWebThe Meta Conversions API sends the results of your ads, such as enquiries, bookings and sales, straight from your website server or CRM to Meta, while the Meta Pixel reports them from the visitor’s browser. Meta recommends using both together, sending the same events through each and matching them so nothing is counted twice, because the Conversions API can capture events the pixel misses.
When ads lose track of results, Facebook and Instagram campaigns end up optimising on partial data. This article explains what each piece does, why results go missing, the ways to set up the Conversions API and what to check afterwards. Facts come from Meta’s own documentation, as at November 2026.
What the Meta Pixel does
Meta describes the pixel as a snippet of JavaScript code that tracks visitor activity on your website. When someone lands on a page, fills in a form or books, the pixel sends that event to Meta from their browser.
Meta says that data can be used to measure how well your ads work, build custom audiences for targeting, and look at how your website turns visitors into enquiries. It also says form field values are not collected unless you send them through Advanced Matching or optional values.
The pixel only works when the page loads properly in the visitor’s browser and the code runs. If either fails, the event is not reported. If you are still setting up your campaigns, start with our guide to Facebook ads for a local business.
What the Meta Conversions API does
Meta’s Conversions API documentation says it connects an advertiser’s marketing data from a server, website platform, mobile app or CRM to Meta’s systems. Events sent this way are linked to a dataset ID and processed like events sent by the pixel.
Because it runs from your systems rather than the browser, it can report things the pixel cannot see at all:
- a booking confirmed in your practice software after a phone call;
- an enquiry that becomes a paying job in your CRM two weeks later;
- an invoice paid, or an in-person sale.
Meta’s documentation says offline events sent this way can be used for measurement and for building custom audiences.
Why ads lose track of results
Meta’s Conversions API best practices say the Conversions API can capture events the pixel may lose to connectivity or page loading problems. In practice, the gaps for a small business usually come from a few places:
- The page did not finish loading before the visitor moved on, so the pixel never fired.
- The result happened somewhere else. A call, a text or a walk-in never touches the website, so the pixel cannot report it.
- The thank-you page changed in a website update, and the pixel event went with it.
- The booking tool runs on another site, so the pixel on your site never sees the confirmation.
A worked example
Say a physio clinic’s ads bring 20 new bookings in a month. Twelve book online through a form on the clinic’s site, five phone the front desk, and three book through a scheduling tool hosted elsewhere. At best the pixel reports the twelve, and fewer if some pages did not load. If the practice software sends every new booking through the Conversions API, Meta has the chance to match all 20 to the people who saw and clicked its ads, depending on the customer details sent. The numbers are made up; count your own channels the same way.
When Meta sees fewer results than really happened, it has less to learn from about who responds to your ads, and your reports understate what the ads did.
Meta Conversions API and the pixel together
Meta’s best practices page says to use the Conversions API in addition to the pixel and to share the same events through both. Its deduplication guide says that, for best ad performance, Meta recommends advertisers implement the Conversions API alongside their pixel.
Sending the same enquiry twice would double count it, so Meta matches the two copies. The deduplication guide sets out how:
- Both copies use the same event name, for example Lead.
- Both carry the same event ID, or a consistent combination of the browser ID (fbp) and your own customer ID (external ID).
- When matching on event ID, Meta only deduplicates events received within 48 hours of each other.
Event Match Quality
Meta gives server events an Event Match Quality score out of 10, which shows how well the customer information you send helps match events to people on its platforms. The best practices page says sending more customer information, such as email and phone number, may raise the score, and that this information should be hashed before it is sent unless you use Meta’s Business SDK. Meta says the score is currently available for web events only.
Ways to set up the Conversions API
| Method | What it involves | Who it suits |
|---|---|---|
| One-click set-up in Events Manager | Meta says that if you have a pixel, you can set up the Conversions API for website events in one click, with no code, configuration or setup fees | Businesses with a pixel already in place and simple website events |
| Through a partner such as your website platform or CRM | Meta’s getting started page refers to third-party partners that offer Conversions API features; check whether yours does | Businesses whose site or CRM already supports it |
| Direct integration | Your server calls Meta’s API with an access token; Meta’s developer docs focus on this | Businesses with custom systems or offline events to send |
Meta’s getting started page says you need a pixel ID, a Meta Business Suite and an access token, and to use the same pixel ID for browser and server events.
Sending CRM results back for lead ads
If you run lead ads with Meta’s instant forms, there is a separate route. Meta’s Conversions API for CRM documentation describes sending down-funnel events from your CRM back to Meta, for example when a lead books or becomes a customer, so the system can learn which leads go further. Meta says this may yield higher quality leads that are more likely to convert.
The same page says the Conversion Leads goal currently works only with lead ads using instant forms, that the stage you optimise for should happen within 28 days of the lead, and that it should have a conversion rate between 1% and 40%. Our guide to getting Facebook lead ads into a CRM covers the first half of that loop.
Privacy: what you should and should not send
The Conversions API makes it easy to send more about each customer than the pixel would. Decide deliberately what goes:
- Send the event (enquiry, booking, purchase) and the hashed contact details Meta asks for.
- Do not send health details, the reason for an appointment, or anything sensitive. A clinic can send “Booked” without saying what for.
- Say in your privacy policy that you share data with advertising platforms, and check the privacy law that applies where you operate.
- Meta offers a Limited Data Use feature for the Conversions API; its documentation links to how it works.
This is general information, not legal advice. Clinics and practices should read our page for health and fitness businesses and take advice on what they can share.
A checklist after set-up
- In Events Manager, confirm events arrive from both the browser and the server.
- Check that duplicates are being matched rather than counted twice.
- Look at the Event Match Quality score and whether more contact fields would help.
- Send a test enquiry yourself and follow it through to the CRM and back to Meta.
- Recheck after any website or form change.
Meta’s numbers are only one view. Compare them with your CRM and analytics, as covered in our guides to marketing attribution and Google Analytics 4.
CentriWeb sets up the tracking, CRM and automation that send real results back to ad platforms, and looks after it when sites and forms change. See our automation work. If your platform’s one-click option covers your events, start there.