__cfduid Cookie Description

Table of Contents

The _cfduid cookie is utilized by sites as a traffic controller. With the ID the _cfduid cookie provides, your site can successfully identify bots or unsafe traffic and block their entry.

Cloudflare Cookie

The _cfduid cookie is a cookie set by the Cloudflare service. Cloudflare is a web infrastructure and website security company that provides content delivery network (CDN) services, internet security, and distributed domain name server (DNS) services. The _cfduid cookie plays a critical role in improving website performance and security. Here’s a detailed breakdown:

  1. Traffic Management:
    • The _cfduid cookie helps Cloudflare identify individual clients behind a shared IP address and apply security settings on a per-client basis. This is particularly useful for identifying and managing traffic coming from shared networks such as those in airports, coffee shops, or other public places.
    • By identifying clients, Cloudflare can ensure that legitimate traffic is not blocked while applying stricter security measures to potentially harmful or bot traffic.
  2. Bot and Unsafe Traffic Identification:
    • The cookie assigns a unique identifier to each client, allowing the website to recognize if a visitor has been previously flagged as a bot or a source of unsafe traffic.
    • Cloudflare’s security algorithms analyze patterns in the incoming traffic and use the data from the _cfduid cookie to differentiate between normal human visitors and malicious bots. This helps in mitigating DDoS attacks and other forms of cyber threats.
  3. Security Settings Application:
    • The _cfduid cookie allows Cloudflare to apply tailored security settings based on the behavior of individual users. For instance, a user identified as potentially harmful can be subjected to additional security checks, while a trusted user can enjoy seamless access to the site.
  4. Enhancing Performance:
    • By effectively managing and filtering traffic, the _cfduid cookie helps improve the performance and speed of the website. Only legitimate traffic is allowed to use the site’s resources, reducing load times and improving the overall user experience.

Privacy and Compliance

  • Data Collection:
    • The _cfduid cookie collects information about the client’s IP address, which is used to enhance security and manage traffic. It does not collect or store personal data that can identify an individual user.
  • GDPR Compliance:
    • While the _cfduid cookie itself is not used for tracking users or storing personal data, it is important to disclose its use in the website’s privacy policy. Websites using Cloudflare should ensure they inform users about the use of such cookies and provide options for consent where necessary.
  • The cookie typically has a lifespan of about 30 days. However, this can be configured by the website administrator according to their security needs.


  • The _cfduid cookie is automatically set by Cloudflare when a website uses Cloudflare’s services. Web developers do not need to manually implement it, as it is part of the Cloudflare infrastructure.

By understanding the role and functionality of the _cfduid cookie, website administrators can better appreciate its importance in enhancing website security and performance, while ensuring compliance with data protection regulations.

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