What’s the difference between first-party and third-party cookies?

In a nutshell

All cookies are associated with a scheme (e.g., http or https), domain (e.g., example.com or acme.com), and optionally a subdomain if the Set Cookie Domain attribute is set.

If a cookie’s scheme and domain match the current page, the cookie is considered to be a same-site / first-party cookie. If they don’t match, the cookie is considered a cross-site / third-party cookie.

Other notes

• How does tracking via third-party cookies work?
• There are various cookie-related regulations that you should be aware of (e.g., informing users how your site uses cookies or allowing them to opt out of receiving cookies). Using specialized cookie banners can help make it easier to comply with these regulations

Sources

• Third-party cookies – MDN