Why IE6 Blocks Cookies and the Role of P3P
Internet Explorer 6, the last widely‑used version of Microsoft’s flagship browser, comes with built‑in privacy controls that were designed to protect users from tracking and unwanted data collection. One of those controls is a strict policy that scrutinizes every cookie the browser receives. If the cookie does not carry a P3P compact policy - or if the compact policy the browser receives is marked as “unsatisfactory” - IE6 will refuse to store the cookie. The effect is that a feature on a site that relies on that cookie simply stops working for a large segment of visitors.
The culprit is almost always third‑party cookies. A third‑party cookie is set by a domain that differs from the page that the user is actually viewing. Think of a banner ad that loads from ads.doubleclick.net while a user browses example.com, or a tracking pixel embedded in an email that the recipient opens in a browser. Because the cookie comes from a different domain, IE6 treats it as third‑party and applies its stricter rules.
By default, IE6 blocks third‑party cookies that either lack a P3P compact policy or that carry a policy that the browser deems unsatisfactory. This default setting is rarely changed by users, so the cookie‑blocking problem becomes a common headache for developers who add cookie‑enabled features such as shopping carts or personalized recommendations.
Enter the Platform for Privacy Preferences Project (P3P). P3P is a W3C recommendation that lets websites publish a machine‑readable statement about how they use personal data. The full policy is written in XML and can be retrieved by a browser or any other P3P‑aware client. In addition to the full policy, P3P defines a compact policy that can be included in the HTTP header that sets a cookie. The compact policy is a short, one‑line representation of the privacy claims that the website makes about the cookie.
When a browser receives a cookie header that also contains a compact policy, it can immediately evaluate whether the policy satisfies the user’s privacy preferences. In IE6, if the compact policy indicates that the cookie may be shared with third parties, used for profiling, or tied to personally identifiable information without an opt‑out mechanism, the cookie is rejected. On the other hand, if the compact policy is deemed satisfactory, the cookie is accepted even in the third‑party context.
Large, popular sites were among the early adopters of P3P. About.com, Yahoo, DoubleClick, Expedia, and AT&T all published P3P policies long before the feature became mainstream. These sites demonstrated that it is possible to publish privacy claims in a structured format and that doing so can protect user privacy while still allowing the site to collect the data it needs. By contrast, sites that omitted a compact policy or left the policy incomplete left themselves vulnerable to IE6’s cookie‑blocking rules.
For developers, the takeaway is simple: if your site uses third‑party cookies, or if you suspect that some of your features rely on third‑party content, you must ensure that every cookie you set comes with a valid, satisfactory compact policy. The rest of this guide walks you through the steps needed to publish a proper P3P policy, add compact policies to your cookies, and troubleshoot the most common issues that can arise when IE6 still blocks your cookies.
Adding P3P Policies and Compact Policies to Your Site
Before you can add a compact policy to a cookie, you need a full privacy statement that the browser can reference. A good starting point is your existing privacy policy. If you don’t already have one, create a concise document that explains what data you collect, why you collect it, how you use it, and what choices visitors have. Even a short policy - just a few paragraphs - provides the foundation for a formal P3P policy.
Next, inventory every cookie your site sets. Cookies come in two flavors: first‑party and third‑party. First‑party cookies are set by the domain you’re visiting. Third‑party cookies come from a different domain, often because your site includes an embedded resource like an ad, a social widget, or a tracking pixel. For each cookie, note its name, domain, path, expiration, and whether it stores any personally identifiable information. Some cookies, such as session identifiers, are innocuous, while others, like advertising identifiers, carry data that can be used for profiling.
Decide whether you want one P3P policy that covers your entire site or multiple policies that reflect different privacy contexts. If you serve distinct types of content - say, an e‑commerce checkout page versus a blog - each may have a different set of data practices. In such cases, a single policy may be too broad. Create separate policies for each context, and link them to the relevant pages using a policy reference file.
Generate the full P3P policy using an online editor. The W3C offers a reference implementation, and IBM’s P3P Policy Editor is a free, user‑friendly tool. In the editor, choose the statements that match your data practices: collect, store, link, transmit, disclose, or keep. Specify which attributes are personally identifiable and whether you offer opt‑out options. When you’re satisfied, the tool will produce an XML document that you save as For each cookie you set, create a compact policy that matches the full policy you just produced. The compact policy is a single line of text, for example: Once the policy files are in place, configure your web server to serve the full policy automatically. Most servers can be set up to expose Validate the entire setup with the W3C P3P Validator. Point the validator at Common pitfalls include missing the Even after following the steps above, you might find that IE6 still blocks cookies. The first thing to check is whether the server actually includes a compact policy in the Next, validate the syntax of the compact policy. Even a minor mistake, such as a missing quotation mark or an invalid claim code, can render the policy unreadable. The W3C P3P Validator can be pointed at the raw header string to confirm correctness. If the validator flags errors, correct the syntax and repeat the test. If the syntax is fine, the issue may be that the compact policy is not considered satisfactory by IE6. IE6 has a built‑in list of “satisfactory” claims. For instance, claims that indicate the cookie is used solely for session management and does not link to other data are acceptable. Claims that suggest the cookie is used for profiling or that the site shares data with third parties without opt‑out options are deemed unsatisfactory. In the P3P Policy Editor, check the “Satisfiable” flag for each claim. Adjust your policy to remove or modify unsatisfactory claims, or add explicit opt‑out statements where possible. Another angle is the user’s own settings. IE6 users can override the default cookie policy in Internet Options → Privacy. They may have chosen a stricter setting, such as “Accept third‑party cookies only if they have a satisfactory compact policy” or “Block all third‑party cookies.” Even a satisfactory compact policy will be blocked if the user’s setting is set to “Accept only first‑party cookies.” In such cases, there is no technical fix; the user must change their preference. Clear the browser’s cookie cache before re‑testing. IE6 sometimes retains old cookie metadata and continues to block new attempts. Use Delete browsing history → Cookies or manually delete all files in Use the IE6 Developer Tools (accessed by pressing Finally, design your application to tolerate cookie blocking. If a required cookie is missing, display a friendly message that explains why the feature isn’t working and offers a workaround. For example, for a shopping cart, let users add items to a session‑based list that does not rely on a persistent cookie. If cookies are blocked, provide a way to continue the experience in a session‑only mode. This approach keeps the site functional while you work out the P3P details. IE6 users who cannot view a privacy report for your site are likely dealing with a misconfigured P3P policy. The privacy report is displayed when IE6 fetches the full policy and the policy reference file successfully. If the policy reference file is missing or malformed, the browser will not show the report. Ensure that your Many browsers, including IE6, rely on the well‑known For visitors who use browsers that do not understand P3P - older versions of IE, Safari, or some mobile browsers - offer a graceful fallback. Display a simple privacy notice on the page that explains what data you collect and how it’s used. Provide links to a full privacy statement and a contact email for questions. This ensures that all users receive some level of transparency, even if they cannot see the IE6 privacy report. Make sure that cookie‑dependent features degrade gracefully. If a user’s cookies are blocked, the site should still load and function at a basic level. For example, allow them to view product listings but disable the ability to add items to a cart. When they return with cookies enabled, the full functionality becomes available. This approach prevents users from abandoning the site because of an unexpected error. Inform users when a cookie is required for a particular feature. When a feature fails due to missing cookies, display a modal or banner that explains the situation: “Our shopping cart uses cookies to remember items. Please enable cookies in your browser to use this feature.” Include a short guide or link to a help page that shows how to enable cookies in IE6. Use analytics to monitor the proportion of visitors encountering cookie issues. By setting up a simple event in Google Analytics that fires when a cookie‑dependent feature fails, you can quantify the impact of IE6 cookie blocking on your overall conversion rates. This data can justify the effort of maintaining P3P or, if the numbers are low, help you decide whether to prioritize other browsers. Long‑term, consider the future of the web. IE6 is gradually being phased out, but it still holds a non‑trivial share in certain markets. If your target audience includes users on older Windows platforms, maintaining P3P compliance remains worthwhile. However, if your analytics show that the majority of traffic comes from newer browsers, you may choose to allocate resources to mobile optimization or progressive enhancement instead. In any case, keep your privacy statements current and ensure they reflect real practices. A misaligned P3P policy not only causes technical headaches but can also erode trust if users discover that the site’s claims do not match its behavior. Regular reviews and updates keep your site compliant, secure, and user‑friendly for everyone, including those still on IE6.p3p.xml in a well‑known location on your server, typically /w3c/p3p.xml
CP="CAO DSP CURa ADMa OUR IND DPI" />. The letters represent claims about data collection (C), sharing (S), or disclosure (D). A handy reference lists the code meanings. Make sure the compact policy is syntactically correct; otherwise, the browser will ignore it.p3p.xml from the well‑known location. For Apache, add a line to .htaccess or the server config: Alias /w3c/p3p.xml /path/to/p3p.xml. For IIS, place the file in the Default Web Site/w3c folder. In addition, configure your server to send the compact policy in the Set-Cookie header for every cookie you set. In Apache, use Header add P3P "CP="..."" for the relevant script. In IIS, add a Set-Cookie header in the response and append ; P3P="CP="...""
http://yourdomain.com/w3c/p3p.xml and review any reported errors. The tool also checks that your server is sending compact policies with every cookie. If you see any syntax errors or missing policies, correct them and re‑run the validator./w3c directory, using the wrong MIME type, or sending the compact policy with a cookie that has a Domain attribute set to a top‑level domain. Also, be careful not to mix the policy with other headers; keep it in a dedicated P3P header. Once the validator reports no issues, your site should be ready to speak P3P to IE6.Troubleshooting When Cookies Still Get Blocked
Set-Cookie header. Use the developer tools in another browser, like Firefox or Chrome, to capture the raw HTTP response. Look for a line that starts with Set-Cookie: and ends with P3P="CP="..."". If that line is missing or the compact policy is incomplete, IE6 will reject the cookie.%userprofile%\AppData\Roaming\Microsoft\Windows\Cookies. Restart IE6 and reload the page to see whether the new cookie is accepted.F12) to capture the HTTP traffic in real time. Look for the Set-Cookie header and verify that the P3P attribute appears as expected. If the header is missing, the problem lies in the server configuration. If it’s present but the cookie still fails, the issue is likely policy satisfaction or user settings.Improving User Experience for IE6 Visitors
p3p.xml file is reachable at http://yourdomain.com/w3c/p3p.xml and that it contains a correct <p3p:policy> element./w3c/p3p.xml location. If you host the file elsewhere, add an alias or redirect to the standard path. Test with the browser by navigating directly to the URL; you should see the XML rendered or served with the text/xml MIME type.
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