Debug Facebook in Chrome DevTools

What Facebook traffic looks like

The Meta Pixel sends image-style hits to /tr, with the pixel ID and event name identifying every request.

Endpoint pattern

facebook.com/tr (or facebook.net/tr); the SDK itself loads from connect.facebook.net/en_US/fbevents.js

Transport

Image-style GET requests with everything in the query string

Key parameters

id numeric pixel ID · ev event name (PageView, ViewContent, AddToCart, Purchase, or custom) · cd business data as a JSON blob (cd={"currency":"DKK","value":"499"}) or bracket notation (cd[currency]=DKK&cd[content_ids]=...) · dl / rl / if document location, referrer, iframe flag

Identity

ud[em] / ud[ph] / ud[fn] Advanced Matching fields: SHA-256 hashes of email, phone, and name · eid event ID deduplicating browser hits against Conversions API server events · coo=true marks a cookie-suppressed pixel

Cookies

fbp carries the _fbp cookie value, Meta's first-party browser ID; fbc carries the click-ID cookie built from the fbclid query parameter on ad landing pages

Debugging Facebook with Event Watcher

• Ships a dedicated Meta Pixel parser: each /tr hit appears in the stream under its ev name.
• The detail view decodes the request: pixel ID, browser ID, and click ID in the overview; cd custom data reconstructed into a nested table (both JSON and bracket formats); Advanced Matching hashes grouped under Identity; page context and SDK metadata under Parsed Data.
• The Cookies section shows _fbp and _fbc being set and sent per hit.
• The Grouped view's Identity pivot collects everything keyed to the same fbp value.

Facebook and consent

Event Watcher checks Meta Pixel hits against marketing consent.

The pixel has no equivalent of Google Consent Mode (no cookieless ping variant), so any /tr request before the CMP grants marketing consent is a real data transmission, marked pre-consent or denied and counted.

Sites that gate the pixel correctly either delay the fbevents.js load through their tag manager or call fbq('consent', 'revoke') until consent arrives. A hit carrying ud hashes before consent is the more serious variant: hashed PII left the browser.

Common debugging scenarios

• Purchase fires but Events Manager shows no value. Open the hit and check the cd table for value and currency. A common failure is cd[value] arriving as a formatted string ("1.299,00") instead of a plain number.
• Deduplication with Conversions API is not working. Compare the eid on the browser hit with the event_id your server sends; the extension shows eid under Request data on every event.
• The pixel fires before the cookie banner is answered. See GA4 fires before consent for the same diagnosis pattern. The marketing-consent check flags the offending /tr hits directly.
• Nobody knows what loads the pixel. The Script Tree view shows whether fbevents.js was loaded by GTM, another tag manager, or a hardcoded snippet, and which events it sent.
• Duplicate PageView events. Group by Event Name and check whether two pixel IDs fire on the same page. Agency pixel plus in-house pixel is the usual cause.