What is the __cflb cookie?
__cflb is an HTTP cookie set by the Cloudflare network when a website uses Cloudflare's Load Balancing service to distribute traffic across multiple servers or data centers. It is not set directly by the site owner, but by the Cloudflare infrastructure sitting in front of the site.
It typically appears on the first interaction between a browser and the site, but only if the site administrator has a Cloudflare load balancer configured — it does not appear on every site that uses Cloudflare, only on those with load balancing enabled.
What data it stores
__cflb stores an internal identifier that Cloudflare uses to link a visitor's successive requests to the same backend server, avoiding session issues caused by routing to different servers. The exact value format is internal to Cloudflare's service and is not publicly documented in detail.
The data is sent to Cloudflare's infrastructure, not to third-party analytics or marketing services. Duration is typically session-based, but this can vary depending on the load balancer configuration.
What it is used for
The cookie's purpose is strictly technical: it provides session persistence (session affinity / sticky sessions) when a site's traffic is distributed across multiple servers via Cloudflare Load Balancing. Without it, a visitor could be routed to different servers on each request, potentially causing lost shopping carts, account logouts, or session errors.
For the site administrator, this cookie contributes to site stability and availability, not to traffic analysis or advertising.
Does it require consent?
In CookieFix's classification, __cflb is categorized as strictly necessary. Under Articles 4-5 of Law 506/2004 (Romania's transposition of the ePrivacy Directive) and ANSPDCP's interpretation, cookies indispensable to a site's technical operation — such as load balancing cookies — do not require prior visitor consent.
- No active banner acceptance is required for this cookie.
- The site administrator must still declare it in the cookie policy, stating its purpose and provider.
- If a site doesn't use Cloudflare load balancing, this cookie should not appear at all.
How to block or delete __cflb
A visitor can delete or block __cflb through browser settings (Chrome, Firefox, Safari, Edge – per-site cookie management), but blocking it may cause session errors on sites using Cloudflare load balancing, since requests could be routed to different servers.
For site administrators, since it is strictly necessary, this cookie should not — and generally cannot — be blocked before consent without breaking site functionality. A consent management platform like CookieFix can automatically classify this cookie as necessary and exclude it from the blocking applied to statistics/marketing scripts, correctly managing only the categories that actually require consent.
Frequently asked questions
It's a technical cookie set by Cloudflare for load balancing, used to route a visitor consistently to the same backend server.
No, it's considered strictly necessary for the site's technical operation, so it doesn't require prior consent, but it must still be listed in the cookie policy.
On sites using Cloudflare load balancing, blocking it can cause session errors, unexpected logouts, or loss of form/cart data.
No, it only appears on sites where the administrator has enabled Cloudflare's Load Balancing service, not on all sites protected by Cloudflare.