All you have to do is...

Open your browser in mobile and type http://IPv4 here:port replace IPv4 here with the computer's IPv4 Address.

How to find it?

In Windows, macOS and Linux, in your Command Prompt/Terminal type ipconfig and get the IPv4 Address.

What's the use?

Previewing your localhost website on your mobile device while both devices are on the same network offers several advantages:

1. Mobile Responsiveness Testing: You can easily check how your website looks and functions on mobile devices, ensuring a better user experience for mobile users.

2. Real-World Testing: Testing on a physical mobile device provides a more accurate representation of how your site will perform in real-world conditions, as opposed to using desktop browser emulators.

3. Immediate Feedback: You can quickly identify and fix issues, such as layout problems, navigation challenges, or performance bottlenecks, in real-time during development.

4. Cross-Browser Testing: Different mobile browsers may render your website slightly differently. Previewing on various mobile browsers helps ensure compatibility across the mobile ecosystem.

5. Reduced Development Time: Identifying and resolving mobile-specific issues early in the development process can save time and effort later on. It minimizes the need for post-development fixes.

6. User-Centric Approach: By testing on a mobile device, you prioritize the user experience on the platform that many users prefer. This can lead to increased user satisfaction and engagement.

7. Debugging and Inspection: Mobile browser developer tools allow you to inspect and debug issues specific to mobile devices, such as touch events, viewport issues, or mobile-specific JavaScript errors.

8. Offline Testing: You can test certain features, such as service workers, offline capabilities, and geolocation services, that require a mobile device to function properly.

9. Device-Specific Testing: Different mobile devices have varying screen sizes, resolutions, and hardware capabilities. Previewing on your own mobile device can help you fine-tune the user experience for your specific target audience.

10. Client Feedback: If you're developing a website for a client, you can easily showcase the progress and functionality of the site to the client without the need for deploying it to a public server.

11. Security and Privacy: Testing on your local network reduces the risk associated with exposing your website to the public internet during development.

In summary, previewing your localhost website on a mobile device provides a convenient and effective way to ensure your website is mobile-friendly, performs well, and offers an optimal user experience for your target audience. It's an essential step in the web development process to create responsive and user-centric websites.