The comprehensive guide explores the application of HTTP status codes in API design, detailing how these codes communicate the state of client requests. It explains the various classes of status codes, ranging from informational (100-199) to server errors (500-599), and their specific roles in handling CRUD operations—Create, Read, Update, and Delete. For instance, the guide discusses using 201 for resource creation and 204 for successful deletions without content. It also covers custom status codes, API changes, and error handling, emphasizing the importance of consistent use for enhanced developer experience. The guide highlights the utility of redirect codes in managing endpoint changes and the significance of status codes in indicating client errors, server issues, and permission-related access denials. Additionally, it underscores the value of tools like Moesif for monitoring and analyzing API traffic to improve client interactions and error management.