> Site index: https://usehardal.com/llms.txt > Every content route also serves markdown at .md # First-Party vs Third-Party Cookies: Key Differences First-party cookies work on the site you visit. Third-party cookies work across sites. Compare their uses, privacy impact, browser support, and examples. Source: https://usehardal.com/third-party-cookies-vs-first-party-cookies Published: 2024-01-26 Updated: 2026-08-22 Author: Berkay Demirbas Category: Privacy --- > **Quick answer:** A first-party cookie belongs to the site in your browser's address bar. A third-party cookie belongs to a different site loaded through an ad, script, image, iframe, or other embedded resource. First-party cookies keep logins, carts, preferences, and site analytics working. Third-party cookies can support cross-site sign-in, advertising, and attribution, but browsers restrict them more heavily. Browser context determines the distinction. A cookie used as first-party on one page can be third-party on another, regardless of which company wrote the code. ## First-party vs third-party cookies at a glance | Difference | First-party cookies | Third-party cookies | |---|---|---| | Site context | The cookie's site matches the top-level site | The cookie's site differs from the top-level site | | Example | You visit `shop.example`, which uses a cookie for `shop.example` | `shop.example` embeds a resource that uses a cookie for `ads.example` | | Common uses | Sessions, shopping carts, language, consent choices, site analytics | Cross-site sign-in, embedded services, advertising, retargeting, attribution | | Cross-site reach | Sent only to the matching site and permitted subdomains | May be recognized when the same third party appears on several sites | | Browser treatment | Generally available, though browser and user limits still apply | Often blocked, restricted, or partitioned | | Typical `SameSite` setting | `Lax` or `Strict` when cross-site access is not needed | `None`, together with `Secure`, when cross-site access is required | | Privacy | Can still identify and track a visitor on one site | Can connect activity across sites when the browser allows it | ## What is a first-party cookie? A first-party cookie is set or read in a same-site context. The cookie's domain and scheme match the page the person is visiting. Suppose someone opens `https://shop.example`. The site's server can return this header: ```http Set-Cookie: session_id=abc123; Path=/; Secure; HttpOnly; SameSite=Lax ``` The browser stores the cookie for `shop.example` and sends it back on matching requests. Another site cannot read that cookie directly. Common first-party cookie examples include: - A session cookie that keeps a customer signed in - A cart cookie that remembers selected products - A preference cookie that stores a language or region - A consent cookie that records a visitor's choices - An analytics cookie that distinguishes visits on the same site Both the server and JavaScript can set first-party cookies. Server-set cookies can use `HttpOnly`, which prevents JavaScript from reading them. The [`Secure`, `HttpOnly`, and `SameSite` attributes](https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Set-Cookie) control how the browser stores and sends a cookie. They do not change a first-party cookie into a third-party cookie. ## What is a third-party cookie? A third-party cookie is used when its site differs from the site in the address bar. It usually arrives through content embedded from another site. For example, `shop.example` might load an iframe from `payments.example`. A response from the embedded site could include: ```http Set-Cookie: payment_session=xyz789; Path=/; Secure; HttpOnly; SameSite=None ``` While the person remains on `shop.example`, the browser treats the `payments.example` cookie as third-party. `shop.example` cannot read its value directly. The browser may send it only to `payments.example`, subject to its privacy settings and storage rules. Third-party cookies have supported several kinds of cross-site behavior: - Recognizing an account inside an embedded sign-in or payment flow - Limiting how often the same ad appears - Attributing a conversion to an ad shown on another site - Retargeting visitors across sites - Saving state for chat, video, maps, and other embedded services The term third-party covers more than advertising. It describes the relationship between the cookie's site and the top-level page. The [MDN guide to third-party cookies](https://developer.mozilla.org/en-US/docs/Web/Privacy/Guides/Third-party_cookies) uses the more precise term **cross-site cookie** for this reason. ## The difference depends on where the cookie is used The same cookie can be first-party on one page and third-party on another. Take a cookie for `video.example`: - On `video.example`, it is first-party. - Inside a `video.example` player embedded on `news.example`, it is third-party. Company ownership does not decide the result. If one company owns both domains, the browser still sees a cross-site context. The reverse can also happen: JavaScript supplied by an analytics vendor can run on `shop.example` and write a cookie for `shop.example`. The browser treats that cookie as first-party even though a vendor supplied the script. This technical classification says where the cookie works. It does not say who receives the data or whether the use respects a person's consent. ## First-party cookies and first-party data describe different things A cookie is a browser storage mechanism. First-party data describes the relationship between an organization and the people it serves. First-party data can include purchases, product usage, support conversations, survey answers, and consented website events collected directly by the organization. It may live in a warehouse, CRM, or analytics platform without any cookie attached. A first-party cookie may hold an identifier that links browser activity to first-party data. It can also feed data to outside vendors. Calling the cookie first-party does not make every downstream use first-party, anonymous, or consent-free. ## Are third-party cookies going away? There is no single deadline across every browser. - **Safari:** WebKit [blocks third-party cookies by default](https://webkit.org/blog/10218/full-third-party-cookie-blocking-and-more/). It provides the Storage Access API for cross-site embeds that need user-approved cookie access. - **Firefox:** Total Cookie Protection [partitions third-party storage by top-level site](https://support.mozilla.org/en-US/kb/total-cookie-protection-and-website-breakage-faq), while Enhanced Tracking Protection blocks known cross-site trackers. - **Chrome:** Google said on April 22, 2025 that it would [keep Chrome's existing user-choice approach](https://privacysandbox.google.com/blog/privacy-sandbox-next-steps) and would not add a new standalone third-party cookie prompt. Chrome Incognito blocks third-party cookies by default, and users can block them in regular browsing. That makes the old claim that Chrome would remove all third-party cookies in 2024 incorrect. Sites should still expect them to be unavailable for a meaningful share of visitors because of browser defaults, privacy settings, extensions, and consent choices. Critical functions should work without unrestricted third-party cookies. Depending on the use case, alternatives include a first-party session, OAuth, the Storage Access API, or partitioned cookies such as CHIPS. ## How to check first-party and third-party cookies Chrome DevTools shows which sites store cookies and whether the browser found a cross-site issue: 1. Open the page in Chrome. 2. Open DevTools, then select **Application**. 3. Under **Storage**, expand **Cookies**. 4. Select each listed origin. A cookie for the top-level site is first-party in that context. A cookie used by another listed site is third-party. 5. Check the `Domain`, `SameSite`, `Secure`, and `Partition Key` columns. Chrome places a warning icon beside affected third-party cookies. 6. Open **Network**, reload the page, select a request, and open its **Cookies** tab to see cookies sent, received, or blocked on that request. Chrome's [cookie inspection guide](https://developer.chrome.com/docs/devtools/application/cookies) documents each field. Searching your code for `SameSite=None` can also uncover cookies intended for cross-site use, but the attribute alone does not tell you how every request uses the cookie. Running `document.cookie` in the Console is not a complete audit. It shows only cookies available to JavaScript for the current document. It omits `HttpOnly` cookies and does not show every cookie used by embedded sites. ## Which type of cookie should you use? Use the narrowest cookie scope that supports the feature. - For authentication, prefer a host-only, server-set first-party cookie with `Secure`, `HttpOnly`, and an appropriate `SameSite` value. - For carts, language, and consent choices, use first-party cookies with only the data and lifetime the feature needs. - For embedded cross-site features, assume unrestricted third-party cookies may be unavailable. Test the flow with third-party cookies blocked before choosing an alternative. - For analytics and attribution, collect consented events through a first-party endpoint and send only approved data to each destination. First-party cookies are more dependable for site-specific functions. Privacy still depends on the purpose, retention period, security controls, consent state, and destinations. ## How server-side tracking fits in Server-side tracking changes how events are collected and routed while browser cookie classifications stay the same. A site can send an event to an endpoint on its own domain, then process and route that event on infrastructure it controls. The setup may use a first-party cookie for session or visitor state, or it may use no cookie for a particular event. Either way, the server must enforce consent and data rules before forwarding anything. Hardal's [first-party stack](https://usehardal.com/first-party-stack) and [server-side analytics](https://usehardal.com/analytics) reduce dependence on third-party browser scripts and cookies. Start by auditing the cookies already on your site, remove the ones no feature needs, and test important journeys with third-party cookies disabled. The [server-side tracking checklist](https://usehardal.com/server-side-checklist) covers the next implementation steps.