What programming language was used to build the first version of Facebook?

The first version of Facebook was primarily built using a combination of programming languages and technologies, with a focus on web development. Some of the key programming languages and technologies used to build the initial version of Facebook include:

1. **PHP:** PHP (Hypertext Preprocessor) was the primary programming language used for server-side scripting and dynamic web page generation. PHP allowed developers to create dynamic and interactive web applications, making it well-suited for building the backend infrastructure of Facebook.

2. **JavaScript:** JavaScript was used for client-side scripting to enhance the interactivity and user experience of the Facebook website. JavaScript was responsible for handling user interactions, performing client-side validation, and dynamically updating content without requiring full page reloads.

3. **HTML/CSS:** HTML (Hypertext Markup Language) and CSS (Cascading Style Sheets) were used for structuring the content and styling the layout of the Facebook website. HTML provided the markup structure for web pages, while CSS was used to define the visual presentation and styling of elements.

4. **MySQL:** MySQL was used as the database management system (DBMS) to store and manage the structured data used by Facebook. MySQL provided a robust and scalable solution for storing user profiles, friend connections, messages, and other data relevant to the platform.

5. **AJAX (Asynchronous JavaScript and XML):** AJAX was employed to implement asynchronous data retrieval and communication between the web browser and the server. AJAX techniques allowed Facebook to fetch and update content dynamically without requiring full page reloads, enhancing the responsiveness and interactivity of the user interface.

These technologies formed the foundation of the first version of Facebook, enabling developers to create a dynamic and interactive social networking platform that revolutionized online communication and social interaction. Over time, Facebook's technology stack evolved and expanded to incorporate additional languages, frameworks, and technologies to support its growth and scalability.

The first version of Facebook was primarily built using PHP for the back-end development and JavaScript for front-end functionality. Additionally, HTML, CSS, and SQL were used for various aspects of the website's design, structure, and data storage.