First-Party vs Third-Party Cookies Explained

When Google announced it would phase out third-party cookies in Chrome, I got calls from three clients the same week asking what it meant for their analytics. The truth is, most website owners don’t fully understand first-party vs third-party cookies — and that’s okay. In this guide, I’ll break down what first-party and third-party cookies actually are, how they differ, and what the future looks like as browsers move toward a cookie-less web.

If you’ve ever seen a cookie consent banner pop up on a website, you’ve already encountered this topic. But there’s a lot more going on behind the scenes than most people realize. Let’s dig in.

What Are Cookies? A Quick Recap

A cookie is a small text file that a website stores on your computer or phone. It contains bits of data — like your login status, language preference, or a unique identifier — so the website can remember you when you come back.

Cookies were invented in 1994 by a Netscape engineer named Lou Montulli. He needed a way for websites to remember things about visitors without storing everything on the server. The idea stuck, and cookies have been a core part of how the web works ever since. You can read the full history on the Wikipedia HTTP cookie article.

There are two main types of cookies based on who sets them: first-party cookies and third-party cookies. The technical mechanism is the same — both are just small text files. The difference is all about who puts them there and why.

First-Party Cookies Explained

A first-party cookie is set by the website you are currently visiting. If you go to example.com, any cookie that comes from example.com is a first-party cookie.

These cookies are essential for making websites work properly. Here are some common uses:

• Keeping you logged in — Without a cookie, you’d have to enter your password on every single page.
• Remembering your shopping cart — Items stay in your cart even if you navigate to a different page.
• Storing your preferences — Things like language, dark mode, or region settings.
• Website analytics — Tools like Google Analytics use first-party cookies to understand how visitors use a site. They track things like which pages you visit and how long you stay.

First-party cookies are generally considered safe and necessary. Most browsers allow them by default because they improve the user experience. Without them, modern websites simply wouldn’t function the way you expect.

From a technical standpoint, first-party cookies are set using the Set-Cookie HTTP header or via JavaScript’s document.cookie API. The MDN Web Docs guide on HTTP cookies has an excellent deep dive if you want to learn the technical details.

Third-Party Cookies Explained

A third-party cookie is set by a domain other than the one you’re visiting. If you’re on example.com and a cookie is set by ads.trackingcompany.com, that’s a third-party cookie.

How does that happen? It’s because most websites load resources from other domains — things like ad banners, social media buttons, analytics scripts, or embedded videos. Each of those external services can set their own cookies on your browser.

Third-party cookies are mainly used for:

• Advertising and retargeting — Ever searched for shoes and then seen shoe ads everywhere? That’s third-party cookies at work. Ad networks use them to track you across multiple websites and build a profile of your interests.
• Cross-site tracking — Analytics and data companies use third-party cookies to follow your browsing behavior across the web.
• Social media widgets — When you see a “Like” or “Share” button on a website, the social media platform may set a cookie to know you visited that page.
• Embedded content — YouTube videos, maps, and other embedded content from third-party domains can set cookies too.

This is where privacy concerns come in. Third-party cookies allow companies to build detailed profiles of your online activity — often without you realizing it. That’s why regulations like the GDPR require websites to get your consent before using them.

First-Party vs Third-Party Cookies: Key Differences

Here’s a side-by-side comparison to make the differences crystal clear:

The key takeaway: first-party cookies help the website you’re on work better. Third-party cookies help other companies learn about your browsing habits.

The Death of Third-Party Cookies

Third-party cookies are on their way out. Here’s a quick timeline of how we got here:

• 2017: Apple’s Safari browser introduced Intelligent Tracking Prevention (ITP), severely limiting third-party cookies.
• 2019: Firefox started blocking third-party tracking cookies by default with Enhanced Tracking Protection.
• 2020: Google announced plans to phase out third-party cookies in Chrome — the world’s most popular browser with over 60% market share.
• 2024-2025: Google rolled out its Privacy Sandbox initiative, introducing new APIs like the Topics API and Attribution Reporting as alternatives to third-party cookies.

In my experience working with clients, this shift caught a lot of people off guard. Many businesses had built their entire marketing strategy around third-party cookie data. When Safari and Firefox blocked them first, it was a wake-up call — but Chrome doing it meant the entire advertising industry had to adapt.

What This Means for Your Website

If you run a website, here’s what you need to know:

Your Analytics Will Still Work

Tools like Google Analytics 4 (GA4) use first-party cookies, not third-party cookies. So your basic website analytics — page views, sessions, traffic sources — will continue working just fine. If you haven’t switched to GA4 yet, check out our beginner’s guide to Google Analytics 4.

Advertising Will Change

If you use display advertising or retargeting campaigns, you’ll need to explore alternatives. Google’s Privacy Sandbox offers new tools, and many advertisers are moving toward contextual advertising (showing ads based on the page content rather than user tracking).

Cookie Consent Still Matters

Even though third-party cookies are disappearing, you still need a proper cookie consent banner. First-party analytics cookies still require consent under GDPR in many cases, and new tracking technologies will have their own consent requirements. The W3C Privacy Interest Group continues to develop standards around web privacy and tracking.

First-Party Data Is More Valuable Than Ever

With third-party data becoming harder to collect, the data you gather directly from your visitors — email signups, account registrations, purchase history — becomes your most valuable asset. Smart businesses are investing in building direct relationships with their audiences.

How to Prepare for a Cookieless Future

Here are practical steps you can take right now:

1. Audit your cookies. Use your browser’s developer tools (press F12, then go to the Application tab) to see what cookies your website sets. Identify which are first-party and which are third-party.
2. Switch to first-party analytics. Make sure your analytics setup uses first-party cookies. GA4 does this by default.
3. Build your email list. Email is a direct channel that doesn’t depend on cookies at all. Start collecting email addresses with valuable lead magnets.
4. Use server-side tracking. Server-side tagging sends data from your server instead of the visitor’s browser, reducing dependence on cookies entirely.
5. Update your consent management. Make sure your cookie consent banner is compliant and clearly explains what data you collect and why.
6. Explore Privacy Sandbox APIs. If you’re an advertiser, start testing Google’s new APIs like Topics and Attribution Reporting as replacements for third-party cookie-based tracking.

I went through this process with one of my clients last year. They were a mid-size e-commerce store relying heavily on retargeting ads. We shifted their strategy toward email marketing and first-party data collection, and within six months they actually saw better conversion rates because they were reaching people who had actively opted in.

Frequently Asked Questions

Are first-party cookies safe?

Yes, first-party cookies are generally safe. They are set by the website you’re visiting and are used for essential functions like keeping you logged in, remembering your preferences, and powering analytics. They cannot track you across other websites. However, you should still be aware of what data a website collects and check their privacy policy.

Can I block third-party cookies in my browser?

Yes, and most modern browsers already do this by default or are in the process of doing so. In Chrome, go to Settings, then Privacy and Security, then Cookies and Other Site Data. In Firefox and Safari, third-party tracking cookies are blocked automatically. Blocking third-party cookies rarely breaks website functionality.

Will blocking third-party cookies affect my website analytics?

No, it won’t. Google Analytics 4 and most modern analytics tools use first-party cookies, which are not affected by third-party cookie blocking. Your visitor counts, page views, and other metrics will continue to work normally. The main impact is on cross-site advertising and retargeting campaigns.

Do I still need a cookie consent banner if third-party cookies go away?

Yes, you likely still need one. Under GDPR and similar privacy laws, you need consent for most types of tracking — including first-party analytics cookies that aren’t strictly necessary for the website to function. Even as third-party cookies disappear, new tracking methods will still require user consent.