Which feature aids in securely storing authentication details in Salesforce integrations?

Named credentials serve as a secure way to manage authentication details in Salesforce integrations. They allow you to define the URL of a callout and store authentication information, such as usernames and passwords, or OAuth tokens, in a centralized manner. By using named credentials, you eliminate the need to hard-code sensitive information directly in your code, which can pose security risks.

Additionally, named credentials provide the capability to handle authentication types automatically and allow you to set up various protocols, including OAuth 2.0. This means that when creating integrations, developers can easily reference named credentials in their API callouts without having to worry about managing the underlying authentication mechanisms themselves.

While custom settings and custom metadata types can be used for storing configuration data, they do not inherently provide the same level of security and ease of use for authentication as named credentials do. Protected custom fields can offer some security for sensitive data but do not address the specific needs of managing integration authentication details effectively.