Rob owns a heating and air conditioning company in Puyallup. Every Monday, his office manager, Jen, goes through the new inquiries and asks each customer how they found the company. At the end of October, her tally for Facebook ads was 30 leads.
Then Rob opened Facebook Ads Manager. It said 18.
Rob’s first thought was that his ads were not working as well as he hoped, and that maybe it was time to cut the budget. Jen’s first thought was that Facebook was wrong. “I talked to these people,” she said. “I know where they came from.”
Jen was almost certainly right. And the reason why is worth understanding, because it affects nearly every business that advertises on Facebook and Instagram. It also affects how well those ads work, not just how good the reports look. (Rob and Jen are an example we made up for this guide, but the gap they found is a common one.)
First, how does Facebook know someone became a lead?
When someone clicks your Facebook ad, they leave Facebook and land on your website. From that moment, Facebook can no longer see what they do, unless your website tells it.
That is the job of the Meta Pixel. The Pixel is a small piece of code added to your website. Think of it as a counter at the door of your shop. When a visitor fills in your form or books an appointment, the Pixel sends a message back to Meta: “The person who clicked your ad just became a lead.”
To connect that visitor with the person who saw the ad, the Pixel relies on the browser: the program the person uses to view your website, such as Chrome or Safari. It stores a small piece of information called a cookie, and it runs in the visitor’s browser every time they load a page.
For years, this worked well. But browsers and phones have changed, and the counter at the door now misses a lot of people.
Five reasons the Pixel misses leads
Let’s meet five of the customers who contacted Rob’s company in October.
Anna uses an ad blocker
Anna has an ad blocker installed in her browser, like many people do. Most ad blockers also block tracking code. When Anna fills in Rob’s form, the Pixel never loads, so Meta never hears about her.
Ben said “Ask App Not to Track” on his iPhone
Since iOS 14.5 in 2021, iPhone apps have had to ask permission before tracking people across other companies’ apps and websites. This is Apple’s App Tracking Transparency, and many people say no. When Ben clicked Rob’s ad inside the Facebook app and later became a lead, much of the connection between the ad and the lead was lost.
Carla uses Safari
Safari includes built-in tracking prevention that limits how long cookies last and what they can do. If Carla clicked the ad on Monday and came back to fill in the form on Thursday, the cookie that linked her to the ad may already be gone.
Dan saw the ad on his phone and filled in the form on his laptop
Dan saw Rob’s ad while scrolling Instagram at lunch. That evening, he searched for Rob’s company on his laptop and filled in the form. To the Pixel, those look like two different people.
Ella called instead
Ella saw the ad, tapped the phone number, and called. She never filled in a form at all. The Pixel only sees what happens on the website, so she is invisible to it.
Each of these is a small gap. Together, they explain how Jen counted 30 leads and Ads Manager counted 18.
Why the wrong number costs more than you think
It is tempting to shrug and say, “As long as I know the real number, who cares what Facebook thinks?” But Meta’s advertising system learns from the leads it can see.
Imagine training a new employee by showing them only some of your best customers. They would build a slightly wrong picture of who your customers are. Meta’s system is the same. When it only sees part of your results, it learns from an incomplete picture. That can lead to:
- Good ads looking weak, and being switched off.
- Meta finding fewer people like your real customers, because it is learning from a smaller, skewed group.
- Your cost per lead looking higher than it really is, which makes the whole channel seem less worthwhile.
Rob nearly cut his budget because of a number that was wrong. That is the real cost of under-reporting.
What the Conversions API does
If the Pixel is a counter at the door, the Conversions API is your office sending Meta a list of new leads directly.
Instead of relying on code running in the visitor’s browser, the Conversions API (often called CAPI) sends conversion information from your server, or from the software you already use, such as your website platform or your CRM. Because it does not depend on the visitor’s browser, ad blockers and browser cookie limits do not affect it in the same way.
Meta recommends using the Pixel and the Conversions API together. The Pixel captures what it can in the browser. The Conversions API fills in the gaps. Meta then combines the two, so each lead is counted once.
The three details that make it work
Turning on the Conversions API is only the start. Three details decide whether it actually helps.
1. Counting each lead once (deduplication)
If both the Pixel and the Conversions API report Anna’s form, Meta needs to know it is one lead, not two. It does this by matching the event name, such as “Lead”, and a shared event ID, a unique reference number sent with both messages, a bit like a receipt number. Meta explains this in its guide to deduplicating Pixel and server events. If the IDs do not match, your leads can be double-counted, which is just as misleading as missing them.
2. Sending enough customer information
To connect a server message with the person who saw your ad, the Conversions API sends details such as the customer’s email address and phone number. These are hashed before they are sent, which means they are turned into a scrambled code that cannot be read back as the original email or number, but can still be matched. The more matching details you send, the better Meta can connect the lead to the right person.
3. Watching your Event Match Quality
In Meta Events Manager, server events get an Event Match Quality score out of 10. It tells you how well the customer information you send can be matched. A low score usually means you are sending too few details, or sending them in the wrong format. One limit to know: the score is shown for website events only, so events you send from a CRM, such as booked jobs, will not get one. Meta’s Conversions API best practices explain how to improve it, and it is the quickest way to see whether your setup is really working.
How to set it up
The good news is that most small businesses do not need to build anything from scratch. Common routes include:
- Shopify: the Facebook & Instagram app turns on the Conversions API when you choose the Enhanced or Maximum data sharing level. The Standard level does not include it.
- WordPress and WooCommerce: Meta’s own integration and several well-known plugins support it. Choose one that sends a shared event ID, so leads are not double-counted.
- Your CRM or lead software: many tools connect to Meta directly. This has an extra benefit we will come to in a moment.
- Conversions API Gateway: set up from Events Manager, but it runs in your own Amazon Web Services (AWS) account and needs AWS and DNS access. That is a lot for a business without technical help, so many use a partner-hosted version instead.
- A developer: the most flexible route, for custom websites or more complex sales processes.
Going further: tell Meta which leads became customers
For a business like Rob’s, a form submission is only the beginning. Some leads become installations, some become small repairs and some go nowhere.
If Rob’s CRM can tell Meta which leads turned into booked jobs, Meta can learn to find more people like his paying customers, not just more people who like filling in forms. Meta supports this through its conversion leads integration for CRMs. It takes a little more setup, but it is one of the most valuable improvements a lead-based business can make.
How to check it is working
Once the Conversions API is set up, Rob’s team can check it in a few minutes:
- Open Events Manager and select the Pixel or dataset.
- Check that key events, such as Lead, show both browser and server as sources.
- Confirm that events are being deduplicated, not counted twice.
- Look at the Event Match Quality score and Meta’s suggestions for improving it.
- Compare a week of leads in Ads Manager with Jen’s own records. The gap should be much smaller.
What the Conversions API will not do
It is worth being honest about the limits. The Conversions API will not make Meta’s numbers match your records perfectly. Some people will always switch devices or call without leaving a trace. It also does not override anyone’s privacy choices. You still need a clear privacy policy and the right consent for the information you share.
What it does is bring Meta’s view much closer to reality, and give the advertising system a far better picture to learn from.
Back to Rob
Rob did not cut his budget. Instead, he had the Conversions API set up through his website, with a shared event ID so leads were counted once, and connected his CRM so Meta could see which leads became jobs.
The following month, the gap between Jen’s tally and Ads Manager became much smaller. More importantly, Rob now had numbers he could trust when deciding where to spend his marketing budget. If you are also weighing up Facebook lead forms against sending people to your website, the next question is which brings better leads.
Frequently asked questions
Do I still need the Meta Pixel if I use the Conversions API?
Yes. Meta recommends using both together, with deduplication, for the most complete picture.
Is the Conversions API only for online stores?
No. It works for any conversion you can record, including form leads, booked appointments and qualified leads from a CRM.
Will the Conversions API lower my cost per lead?
It can help over time, because Meta learns from more complete information. The first change you notice is usually in reporting: you start seeing results that were already happening.
Want your Meta tracking checked?
At Around29, we set up the Meta Pixel and the Conversions API on the Facebook & Instagram ads campaigns we run. If you serve Tacoma or the South Sound, see our Facebook & Instagram ads page, or run a free audit to see where your marketing stands today.