When you view someone's Instagram story, the user whose story you viewed can see that you viewed it, unless your account is private and they follow you. Third-party tools or apps, such as Inviewer, that claim to offer anonymous viewing of stories may exist, but using them could potentially violate Instagram's terms of service. Additionally, using such tools may compromise the security and privacy of your account as they often require you to log in using your Instagram credentials, which can be misused or compromised.