First-Party vs Third-Party Cookies: What Your Cookie Policy Needs to Say About Each

Most cookie policies list cookies the way a grocery receipt lists items: name, purpose, duration, done. What that flat list usually skips is a distinction that actually changes what the law requires you to disclose and how: whether the cookie was set by your own domain or by someone else's. First-party and third-party cookies aren't just a technical curiosity. They trigger different consent rules, different disclosure obligations, and increasingly different browser behavior, and a policy that doesn't separate them is quietly under-disclosing one category or the other.

Here's what the distinction actually is, why it matters legally, and what your cookie policy needs to say about each side of it.

What "first-party" and "third-party" actually means

The distinction has nothing to do with what a cookie does, how long it lasts, or how sensitive the data in it is. It's entirely about which domain set the cookie relative to the site the visitor is on.

A first-party cookie is set by the domain shown in the browser's address bar, the site the visitor actually navigated to. If a visitor is on yourbusiness.com and yourbusiness.com sets a cookie to remember their login session or their shopping cart, that's a first-party cookie, full stop, regardless of whether it's a session cookie that expires when the tab closes or a persistent one that survives for a year.

A third-party cookie is set by a domain other than the one shown in the address bar, typically because a script embedded on the page (an ad tag, a social media widget, an analytics snippet, a chat plugin) sets its own cookie from its own domain while the visitor is still on yours. A visitor on yourbusiness.com who gets a cookie from doubleclick.net or facebook.com, because your page loaded an ad pixel or a "Like" button from one of those domains, is picking up a third-party cookie without ever visiting either site directly.

It's worth separating this from session versus persistent, a different axis entirely that describes how long a cookie lives, not who set it. A cookie can be first-party and persistent (a login token that keeps you signed in for thirty days), first-party and session-only (a cart token that clears when you close the tab), third-party and persistent (an ad network's tracking cookie that follows a browser across sites for months), or third-party and session-only. Crossing these two axes is what a real cookie audit produces: a table of cookies each tagged on both dimensions, not one.

Why the distinction changes what your policy has to say

The first-party/third-party line matters because two different bodies of law hook into it differently, and a policy that ignores the distinction tends to under-serve one of them.

Under the EU's ePrivacy Directive (the actual law behind "cookie consent," GDPR mostly governs what happens to the data afterward) and UK PECR, prior consent is required before any non-essential cookie is set, first-party or third-party alike, with a narrow exemption for cookies strictly necessary to a service the visitor asked for. In practice, though, first-party cookies serving your own core functionality (session tokens, load balancing, a shopping cart) are the ones most likely to qualify for that strictly-necessary exemption and skip the consent requirement entirely. Third-party cookies serving analytics or advertising almost never do, because their purpose serves the third party's business, not the specific service the visitor asked your site for. That's why a compliant consent banner categorizes cookies (strictly necessary, functional, analytics, marketing) rather than asking one blanket yes/no: the categories are doing double duty as a proxy for first-party-necessary versus third-party-optional.

Under CCPA and CPRA, the trigger is different but the first-party/third-party line still does real work. Sharing data with a third party for cross-context behavioral advertising, the kind of thing third-party ad and retargeting cookies exist to do, is what pulls a business into CCPA's "sale" or "sharing" definitions and requires a "Do Not Sell or Share My Personal Information" link or an opt-out preference signal. A first-party analytics cookie that never leaves your own systems typically doesn't trigger that same obligation, because no cross-context sharing with an outside company is happening.

Regulator guidance reinforces the same split from the disclosure side. The UK ICO and France's CNIL have both said, in slightly different words, that "third-party cookies" or "advertising partners" as a category label isn't enough: a compliant disclosure names the actual vendors setting third-party cookies, not just the function they serve. First-party cookies don't carry that same naming burden in the same way, since there's no separate company to identify. Your business is the party, and describing the cookie's own purpose is the whole disclosure.

How to structure the two sections of your policy

Given that split, a cookie policy, the document itself, not the consent banner in front of it, reads better and discloses more accurately when it treats first-party and third-party cookies as two separate sections rather than one merged table, even though a single table with a "party" column can technically work too. The content each section needs to carry is different enough that separating them tends to produce a more complete result.

The first-party section should describe cookies by the purpose they serve on your own site: authentication and session management, shopping cart persistence, load balancing, saved preferences (language, currency, layout), and any first-party analytics you run directly rather than through a third-party tag. Since you control these cookies entirely, this section is straightforward to write accurately, it's just a matter of listing what your own application actually sets, which a look at your session and application cookies (visible in any browser's developer tools under Application or Storage) will confirm.

The third-party section is where policies most often fall short, because it requires naming names, not just categories. Every embedded script that sets its own cookie, analytics platforms (Google Analytics, and similar), advertising and retargeting networks, social media embeds (a Facebook Like button or an embedded Instagram post sets cookies from those companies' domains even if the visitor never clicks anything), and chat or support widgets from an outside vendor, needs to appear as a named entry, along with what that vendor does with the data and, ideally, a link to that vendor's own privacy policy for further detail.

That last row is worth a policy owner's attention even outside the legal angle. Safari's Intelligent Tracking Prevention has blocked most third-party cookies by default for years, and Firefox's Enhanced Tracking Protection does the same. A cookie policy that lists a dozen third-party advertising cookies your ad network claims to set may be describing something that a large share of your actual visitors, on Safari and Firefox, never receive at all. That doesn't remove the disclosure obligation for the vendors that do still fire, but it's a reason to keep the third-party list current rather than copying it once from a vendor's documentation and leaving it untouched, since ad-tech vendors change what they set more often than most sites update their cookie policy.

Keeping the two lists accurate over time

Both lists drift, but they drift for different reasons. Your first-party list changes when your own engineering team adds a feature that needs a new cookie, something a code review or a release checklist can catch. Your third-party list changes whenever a vendor updates their own tag, adds a sub-cookie, or gets acquired and starts setting cookies from a new domain, none of which shows up in your own deploy log. A periodic scan of your live site's actual cookie traffic, not just a memory of what you integrated two years ago, is the only reliable way to keep the third-party section honest, and it's worth treating as a recurring task rather than a one-time audit done at launch.

Once you have both lists current, writing the policy itself is mostly a matter of organizing what you found: first-party purposes in one section, named third-party vendors in another, and a category label on each entry (strictly necessary, functional, analytics, marketing) that your consent banner can reference directly, so the categories a visitor sees in the banner and the categories described in the policy actually match. Our Cookie Policy Generator builds that structure by default, first-party and third-party cookies separated, vendors named rather than grouped into a vague "advertising partners" line, so the policy it produces holds up against the same scrutiny a regulator or a security researcher would apply by simply comparing what your site sets to what your policy says it sets.

The information in this article is for informational purposes only and should not be construed as legal advice on any matter, and does not create a lawyer-client relationship.