ChangeTheHeaders for Safari

ChangeTheHeaders is a Safari extension for iOS, iPadOS, macOS, and visionOS that allows you to customize HTTP request headers such as Accept, Accept-Language, Cookie, and User-Agent. You can set different request headers for specific URL domains and for specific resource types, such as audio and video, iframes, or images. Your settings can be synced to all of your devices via iCloud. Made by indie developer Jeff Johnson, known for StopTheMadness Pro. The support link has documentation and my email address.