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3 | 3 | title: Cookies |
4 | 4 | description: Cookies chapter of the 2025 Web Almanac covering the prevalence and structure of cookies on the web. |
5 | 5 | hero_alt: Hero image of Web Almanac characters carrying a large cookie, while crumbs are thrown off by another character. Another Web Almanac character is following the trail of cookies with a detective hat and a magnifying glass. |
6 | | -authors: [] |
| 6 | +authors: [yohhaan,ajackley] |
7 | 7 | reviewers: [] |
8 | | -analysts: [] |
| 8 | +analysts: [ChrisBeeti] |
9 | 9 | editors: [] |
10 | 10 | translators: [] |
11 | 11 | results: https://docs.google.com/spreadsheets/d/1ZirsnaXgbOMzBmt0X2eMMu3rVJvWCtQgE7pNG7fKcvc/edit |
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18 | | -featured_stat_label_3: ... |
19 | | -doi: ... |
| 12 | +yohhaan_bio: Yohan Beugin is a Ph.D. student in the Department of Computer Sciences at the University of Wisconsin–Madison where he is a member of the Security and Privacy Research Group and advised by Prof. Patrick McDaniel. He is interested in building more secure, privacy-preserving, and trustworthy systems. His current research so far has focused on security of open-sourec software as well as tracking and privacy in online advertising. |
| 13 | +ajackley_bio: Anne Jackley is ...TODO... |
| 14 | +featured_quote: ...TODO |
| 15 | +featured_stat_1: ...TODO |
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| 17 | +featured_stat_2: ...TODO |
| 18 | +featured_stat_label_2: ...TODO |
| 19 | +featured_stat_3: ...TODO |
| 20 | +featured_stat_label_3: ...TODO |
| 21 | +doi: ...TODO |
20 | 22 | --- |
| 23 | + |
| 24 | +## Introduction |
| 25 | + |
| 26 | +[Cookies](https://developer.mozilla.org/docs/Web/HTTP/Cookies) allow websites to save data and maintain state information across HTTP requests, a stateless protocol. Web applications use cookies for several purposes, like authentication, fraud prevention and security, or remembering preferences and user choices, etc. However, ever since their introduction in the mid-1990s, cookies have also played a dominant role in online tracking of web users. |
| 27 | + |
| 28 | +Over the years, browser vendors such as Brave, Firefox, and Safari have imposed restrictions, partitioned, and removed third-party cookies. If initially Google Chrome appeared to follow in these steps by announcing [plans to block all third-party cookies](https://blog.chromium.org/2020/01/building-more-private-web-path-towards.html), several delays and postponements later, Google eventually decided to [maintain their current approach in Chrome](https://privacysandbox.com/news/update-on-plans-for-privacy-sandbox-technologies/). |
| 29 | + |
| 30 | +As a result, cookies—the focus of this 2025 Web Almanac Chapter—remain an essential component in today's web landscape. Next, we measure the prevalence and structure of web cookies encountered while visiting the top one million (top 1M) websites during the HTTP Archive crawl of July 2025. |
| 31 | + |
| 32 | +## Background |
| 33 | + |
| 34 | +To avoid repetitions and overlap here with concepts and definitions from the 2024 Cookies chapter, we refer interested readers to last year's [Definitions section](../2024/cookies#definitions) for an overview of the different types of cookies and the privacy and security risks they can pose. |
| 35 | + |
| 36 | +{# TODO check that previous link to 2024 is correct #} |
| 37 | + |
| 38 | +## First and third-party prevalence |
| 39 | + |
| 40 | +## Cookie attributes |
| 41 | + |
| 42 | +## Cookie prefixes |
| 43 | + |
| 44 | +## Top first and third-party cookies and domains setting them |
| 45 | + |
| 46 | +## Number of cookies set by websites |
| 47 | + |
| 48 | +## Size of cookies |
| 49 | + |
| 50 | +## Persistence (expiration) |
| 51 | + |
| 52 | +## Conclusion |
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