Invisible cookies: partitioned cookies and developing a universal extension manager

The author shares their experience developing CookieTin, a cross-browser extension for cookie management, created as a modern alternative to the outdated Cookie Quick Manager. The main challenge addressed is that modern browsers use 'partitioned cookies,' which often remain invisible to legacy data management tools. The article details how these partitions work, why they complicate data clearing, and how to access them via the WebExtensions API. The author also discusses the technical hurdles encountered while adapting the extension for Firefox, Chrome, and Edge. This article is a valuable resource for browser extension developers and users who want to better control their online privacy by understanding how modern browsers store data.