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How to set up the Meta Conversions API with event deduplication

Live guide · Checked 28 October 2026 · Updated 28 October 2026 · Checked every week against Meta's own help pages

Send leads to Meta from your server as well as the browser, using the same event ID, so Meta counts every lead once, even when ad blockers or iPhones hide the pixel.

Time

40 minutes

You will need

• The Meta Pixel sending Lead with an eventID (previous Secret Setup)
• A server, CRM or automation tool that can send a web request when a lead arrives
• Admin access to Meta Events Manager

Stuck?

Troubleshooting or ask us a question

Step by step

1. Make an access token

   In Meta Events Manager, open your pixel > Settings, scroll to Conversions API and click Generate access token. Copy it and keep it somewhere safe, like a password: never put it in your site's code.

2. Or use a no-code setup first

   In the same place, Set up with Conversions API Gateway or a partner (Shopify, WordPress, HubSpot and others) does this without code. If your platform is listed, use it and skip to the dedup check. The steps below are for your own server.

3. Send the lead from your server

   When a lead arrives on your server, send it to Meta. Use the same lead_id you pushed to the dataLayer as event_id:

   JavaScriptCopy

   // Node 18+ (or a Cloudflare Worker). Hash personal details with SHA-256 first.
   const sha = async (s) => [...new Uint8Array(await crypto.subtle.digest('SHA-256', new TextEncoder().encode(s.trim().toLowerCase())))].map(b => b.toString(16).padStart(2, '0')).join('');
   
   await fetch('https://graph.facebook.com/v21.0/YOUR_PIXEL_ID/events?access_token=' + process.env.META_CAPI_TOKEN, {
     method: 'POST',
     headers: { 'content-type': 'application/json' },
     body: JSON.stringify({
       data: [{
         event_name: 'Lead',                         // must match the browser event name exactly
         event_time: Math.floor(Date.now() / 1000),
         event_id: lead.lead_id,                      // the same id the pixel sent as eventID
         action_source: 'website',
         event_source_url: lead.page_url,
         user_data: {
           em: [await sha(lead.email)],
           ph: lead.phone ? [await sha(lead.phone.replace(/\D/g, ''))] : undefined,
           client_ip_address: lead.ip,
           client_user_agent: lead.user_agent,
           fbp: lead.fbp,                             // the _fbp cookie
           fbc: lead.fbc                              // the _fbc cookie, if there is one
         },
         custom_data: { value: lead.value, currency: 'GBP' }
       }]
     })
   });

4. Send the lead_id and cookies with the form

   Your server needs the lead_id and Meta's cookies from the browser. Add hidden fields lead_idCopy, fbpCopy and fbcCopy to the form and fill them before it's sent:

   JavaScriptCopy

   function cookie(n) { return (document.cookie.match('(^|; )' + n + '=([^;]*)') || [])[2] || ''; }
   var id = 'L-' + Date.now();
   document.querySelectorAll('form').forEach(function (f) {
     f.addEventListener('submit', function () {
       [['lead_id', id], ['fbp', cookie('_fbp')], ['fbc', cookie('_fbc')]].forEach(function (p) {
         var el = f.querySelector('input[name="' + p[0] + '"]'); if (el) el.value = p[1];
       });
     });
   });

   Use the same idCopy in your dataLayer push, so the browser and server copies match.

5. Test with a test code

   In Events Manager open Test events and copy the test event code (like TEST12345Copy). Add "test_event_code": "TEST12345"Copy next to dataCopy in the request, send a test lead and watch it appear marked Server. Remove the test code after.

6. Check deduplication

   Send a real test lead with the pixel on. In Events Manager > Overview, click Lead: after a few hours it shows Browser and Server with a Deduplicated note. If the counts double instead, the event names or IDs don't match.

7. Watch Event Match Quality

   On the same page, Event Match Quality shows how well Meta matches your leads to people. Sending email, phone, fbp and fbc usually gets it to Good or Great.