User interface with automatic highlighting of content updates

Users that visit websites or other content at different times often see content with minor updates. For example, a shopping website may display a list of items and corresponding prices, and the prices may change between multiple user visits. While some websites include built-in functionality to notify users of such changes, no general purpose solution is available to alert users. This disclosure describes techniques to detect the context of a user visit to a website or other content, and determine changes to the webpage since a prior visit. With user permission, the UI of the website is modified to highlight the differences or the changes are indicated to the user, e.g., via a notification. Data from user visits is obtained and stored with user permission in order to determine changes