Guides, demos and tools to help you understand how cookies work.
Understand HTTP cookies: how they're set by a web server, then stored and sent by a web browser.
A third-party cookie is from a site that's different from the site you're visiting. What does that mean in practice?
Cookies can be blocked by browser design, Enterprise policy, or user choice. This article explains how.
Chrome tools to help you understand cookie usage on your site.

In depth

Cookies can include attributes to control if they're set, and when they expire.
Learn more
The web uses the HTTP protocol to transfer resources and set cookies. How does that work?
Learn more
First-party cookies, third-party cookies, cross-site tracking.

Basic cookie
demos

Cookies are set in response to requests for the image and iframe on the demo page.
👉 1pc.glitch.me
The demo page includes an image and an iframe from a different (third-party) site.
👉 3pc.glitch.me
JavaScript included on this page sets a cookie.
👉 javascript-cookie.glitch.me
Both sites set a cookie in response to requests, using the default SameSite value Lax.
👉 samesite-a.glitch.me
👉 samesite-b.glitch.me
These two pages demonstrate user tracking with an iframe.
👉 example-a.glitch.me
👉 example-b.glitch.me
Both pages include a single-pixel image, which allows a cookie to track activity on sites that include the image.
👉 tracking-pixel-a.glitch.me
👉 tracking-pixel-b.glitch.me
JavaScript included on this page makes a cross-site fetch() call, which sets a cookie in response.
👉 fetch-cookie.glitch.me