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Feature Policies are soon to change name to "Permission Policies" Feature Policies comprise a set of rules you can selectively define in relation to browser features and APIs to enforce the desired best practices for your website. For instance, you can ensure that under no conditions a user on a device with a small viewport will receive an oversized, unoptimized image - this effectively prevents layout thrashing and avoids wasting user’s bandwidth. Feature Policy is a powerful tool that allows you to control the use of a variety of browser features.