Google Chrome is again retaining site data from google.com despite a user setting configured to delete all site data when the browser closes, according to testing by Jeff Johnson of Lapcat Software published September 5, 2026. The issue reproduces a similar bug from 2020 that was fixed after Johnson's prior report.
Jeff Johnson documented the exact Chrome setting he tested - the 'Delete site data and permissions for www.google.com and its installed app' checkbox was enabled at chrome://settings/content/siteData, showing the configuration intended to prevent persistence
This interface view illustrates how Chrome tracks and displays site storage information, providing the context for understanding the persistent 1,216 KB of google.com data despite deletion attempts
Johnson configured DuckDuckGo as the default search engine in Chrome to eliminate search-engine-related variables from the test, setting up the controlled environment for reproducing the site data persistence bug
Johnson tested Chrome 152.0.7977.83 on two Macs with the "Delete data sites have saved to your device when you close all windows" setting enabled at chrome://settings/content/siteData. He was not signed into Chrome and had changed the default search engine to DuckDuckGo to rule out search-engine-related causes. After performing a Google search and closing the single Chrome window, he found that google.com site data—cookies, local storage, and session storage—persisted in ~/Library/Application Support/Google/Chrome/Default and remained after quitting and relaunching Chrome. The behavior repeated when he deleted the data and retested.
The root cause is Chrome's Compression Dictionary Transport feature, a Chromium-specific web technology. As Johnson noted in a September 16 addendum citing a public Chromium bug report filed by a third party: "the bug is caused by Compression Dictionary Transport... google.com is an early adopter of Compression Dictionary Transport." The shared dictionaries created by this feature constitute additional storage that Chrome does not correctly clear when closing windows. A Chromium contributor confirmed in the current Hacker News discussion: "It's not just Google.com but any site using Compression Dictionary Transport... The shared dictionaries are an additional storage added with this feature but are not getting correctly cleared on close. A fix is being worked on."
The screenshot captured in Johnson's test shows the actual storage amount after closing the Chrome window with site data deletion enabled, demonstrating the bug's effect with 1,216 KB of google.com data remaining
The screenshot from Johnson's test setup shows the initial state of site data storage (0 B) before the search and browser close operation, providing the baseline for comparison with the persisted 1,216 KB after the bug occurred
This mirrors a 2020 bug where Chrome exempted Google-owned sites (Search and YouTube) from the "Clear cookies and site data when you quit Chrome" setting. That bug, also documented by Johnson, was traced to a Chromium commit and partially fixed in Chrome 86 for youtube.com, though google.com remained affected for a time. The current manifestation is distinct: it stems from a newer compression feature rather than the same code path.
Johnson emphasizes the recurrence reflects a quality-assurance gap given Google's resources. The Compression Dictionary Transport explanation means the exemption is not limited to Google properties—any site adopting the feature would exhibit the same persistence—but google.com's early adoption made it the first observed case. A fix for the clearing logic is underway in the Chromium project.