What fbclid Is
fbclid is the click ID Meta attaches to outbound links. When someone taps a link on Facebook or Instagram that leads to an external website, Meta appends fbclid= and a unique value to the URL. Meta keeps a record of the click, and the value lets a later conversion be tied back to it.
Meta introduced the parameter in 2018. It shows up on paid and organic clicks alike, so it identifies Meta-referred traffic rather than ad traffic specifically.
How fbclid Is Used on the Web
On websites, the Meta Pixel and server-side integrations read the fbclid from the URL and store it in a first-party cookie called _fbc. The stored value combines a version prefix, the time the click was first seen and the fbclid itself.
When the site later sends a conversion to Meta through the Conversions API, it includes the fbc value with the event. Meta uses it as one of its strongest match keys, alongside hashed customer data, to link the event to the original click and the ad behind it. Higher match quality means more conversions attributed and better campaign optimization.
fbclid and App Attribution
For mobile apps, fbclid plays a narrower role than it does on the web.
Standard app install campaigns do not rely on fbclid. Meta is a self-attributing network: it decides which installs its ads drove and reports them to linked MMPs. On Android, Meta also places encrypted campaign data in the Google Play Install Referrer, which an MMP can decrypt with a key from Meta.
Web-to-app journeys are where fbclid matters. A user taps a Meta ad, lands on a web page, then installs the app. If the page keeps the fbclid and passes it into the install flow, the MMP can match the install to the click deterministically and send the install and later events back to Meta with the right click data.
Linkrunner reads ad click IDs such as fbclid and gclid as part of deterministic matching, before IP and user-agent fallback. For Meta, it also sends events through the Conversions API, decrypts the install referrer and syncs spend every 30 minutes. Meta web-to-app campaigns can be created automatically with spend sync and the Conversions API. See Google and Meta ads and web-to-app.
Where fbclid Gets Lost
- Redirects that drop query parameters between the ad and the landing page.
- Landing pages that rewrite or clean the URL before scripts can read it.
- Browser privacy features that strip known click IDs, for example in private browsing or links opened from mail and messages.
- In-app browsers, where a user who switches to the default browser may arrive without the original parameters.
Each of these lowers the share of conversions with an fbclid, which lowers Meta's match rate. Testing the full click path on real devices is the fastest way to find which one applies.
Practical Tips
- Keep query parameters on every redirect from ad to landing page to store link.
- Store fbclid as soon as the page loads, before any navigation.
- Send the fbc value with Conversions API events, along with hashed customer data where you have consent.
- Send each event to Meta from one source. If you also run the Facebook SDK in your app, turn off its automatic event logging so Meta does not receive the same in-app events twice.