You lose signals when Meta only learns about some of your conversions. The Pixel runs in the browser and can miss events because of network issues or page-loading errors. The Conversions API sends the same events from your server, and Meta recommends using both, with deduplication. Fewer signals mean weaker optimisation and reports that don't match your sales.
Meta's algorithm optimises on the events it receives. If events are missing, duplicated or poorly chosen, the campaign learns the wrong thing. Below: what each tool does, how to combine them and what to check in Events Manager.
What are the Meta Pixel and the Conversions API?
The Meta Pixel is code that runs on your site, in the visitor's browser, and sends events such as a page view, add to cart or purchase. The Conversions API creates a direct connection between your marketing data (from your server, website platform, app or CRM) and the Meta systems that optimise delivery, decrease cost per result and measure outcomes. It accepts events from websites, physical stores, email, business chat, phone, apps and offline.
Why does the Pixel miss events?
Because it depends on what happens in the browser. Meta explains that a redundant setup helps because the Conversions API can capture website events the Pixel might miss due to network issues or page-loading errors. Its best-practice guide also mentions events lost to browser restrictions or technical issues.
How do lost signals affect campaigns?
Twice over: in reporting, where you see fewer conversions than you had, and in optimisation, where the algorithm has fewer examples to learn who buys. It's not only a Meta problem: in one of our case studies, an online store in Hungary, Google Ads was tracking fewer than 10% of conversions correctly when we started, and fixing measurement was one of the first steps.
Which event you send matters too. In our business consultant case study, two campaign configurations documented in the same reports cost €3.04 and about €384.50 per lead. It isn't a before/after comparison, but it shows that the event has to be technically reliable, frequent enough and tied to real intent.
How do you run the Pixel and the Conversions API together?
- Send the same key events through both, for example purchase, initiate checkout and contact. Meta calls this a redundant setup.
- Give each event a unique ID: eventID in the Pixel and event_id in the Conversions API, with the same value.
- Use the same event name in both (event in the Pixel, event_name in the API).
- Send server events in real time or as close to it as possible. Deduplication only works if events arrive within 48 hours of the first event with that event_id.
- Monitor event coverage in Events Manager. Meta recommends aiming for a 75% coverage ratio of Conversions API events to Pixel events.
What is Event Match Quality and how do you raise it?
Event Match Quality shows how effectively your server events can be matched to Meta accounts. Meta calculates a score from 0 to 10 from the quality of the customer information you send and the share of events matched, based on the last 48 hours. Email and click ID are among the high-priority parameters. Contact details must be hashed, as described in the developer documentation.
Does the Conversions API get around consent?
No. Meta's terms require you to have the lawful right to collect, use and share the data, to hash contact information and to obtain any necessary consents before sharing it. Sending from the server changes the route the data takes, not the rules. If you use a cookie banner, check how it connects to measurement too; see our guide to Consent Mode v2 and your cookie banner.
Illustrative example: a contact form
A hypothetical example. A service website fires the Lead event from the Pixel when the thank-you page loads. If the page loads slowly or the visitor closes the window, the event is lost. With the Conversions API, the server sends the same Lead when the form reaches the CRM, with the same event_id, and Meta keeps a single event. From the CRM you can then also send the moment that matters commercially: the customer who signed.
Checklist: what to check in Events Manager
- Do your key events arrive from both the browser and the server?
- Does each event carry the same event_id in both sources?
- Does the event count resemble your real number of orders or leads?
- Is the Event Match Quality score for your main events rising or falling?
- Do server events arrive on time, not hours late?
- Do you share data only with a lawful basis and the necessary consents?
What next
Setting up the Pixel and the Conversions API properly is part of marketing measurement. If you want it built together with your campaigns, see how we run performance marketing.
Frequently asked questions
Do I still need the Pixel if I use the Conversions API?
Meta recommends using both in a redundant setup: the same events shared through the Pixel and the Conversions API. The API can catch events the Pixel misses, and the Pixel remains the source of browser events. To avoid counting the same conversion twice, you need deduplication with a matching event ID and event name.
How do I avoid double-counting conversions?
Send eventID in the Pixel and event_id in the Conversions API with the same value, plus the same event name. Meta generally keeps the event it receives first. Deduplication only works if the server event arrives within 48 hours of the first event with that ID, so send it as quickly as you can.
What's a good Event Match Quality score?
Meta scores it from 0 to 10 and says better matching makes it more likely events link to Meta accounts, which can improve delivery and cost per action. It doesn't set a universal threshold. Track the trend for your main events and apply the recommendations in Events Manager.
Can I use the Conversions API without consent?
The Conversions API doesn't change data-protection rules. Meta's terms require you to have the lawful right to collect, use and share the data, to hash contact details and to obtain any necessary consents before sharing them. For your compliance plan, Meta advises working with your own legal counsel.
Can I send sales from my CRM to Meta?
Yes. The Conversions API accepts events from several sources, including CRM, physical stores, phone and offline. That lets you send not just the lead but the moment it becomes a customer, so the campaign can be judged, and in some setups optimised, on the commercial outcome rather than the form fill.