Abstract: Access is provided to a first tier of limited persistent storage at a server. A first set of data from the first tier is synchronized across devices associated with a user account. Access is provided to a second tier of persistent storage on a local, tangible non-volatile storage medium, and to a third tier of temporary storage on a local, tangible volatile storage medium. A web browser receives a storage request from a web application or browser extension. The request includes a type of a tier of data storage associated with a feature of the web application or browser extension. The type includes at least one of the first tier of remote limited persistent storage, the second tier of local persistent storage, or the third tier of local temporary storage. At least one feature of the web application or browser extension is associated with the tier of data storage.

Abstract: A rendering engine may be configured to execute, within a execution environment, a page script of a page to be rendered within a browser interface, the page script configured to interact with a page model to implement the rendering. An extension manager may be configured to execute an extension file which modifies a functionality of a browser application in association with the rendering of the page, including detecting a content script associated with the extension file which, during execution, interacts with the page model. An environment manager may be configured to evaluate the page, for example using a blacklist, prior to execution of the content script by the rendering engine.

Abstract: Access is provided to a first tier of limited persistent storage at a server. A first set of data from the first tier is synchronized across devices associated with a user account. Access is provided to a second tier of persistent storage on a local, tangible non-volatile storage medium, and to a third tier of temporary storage on a local, tangible volatile storage medium. A web browser receives a storage request from a web application or browser extension. The request includes a type of a tier of data storage associated with a feature of the web application or browser extension. The type includes at least one of the first tier of remote limited persistent storage, the second tier of local persistent storage, or the third tier of local temporary storage. At least one feature of the web application or browser extension is associated with the tier of data storage.