What Happens When You Type a URL Into Your Browser?

The diagram above illustrates the steps.

• •Bob enters a URL into the browser and hits Enter. In this example, the URL is composed of 4 parts:

- scheme - http://. This tells the browser to send a connection to the server using HTTP.

- domain - example.com. This is the domain name of the site.

- path - product/electric. It is the path on the server to the requested resource: phone.

- resource - phone. It is the name of the resource Bob wants to visit.

• •The browser looks up the IP address for the domain with a domain name system (DNS) lookup. To make the lookup process fast, data is cached at different layers: browser cache, OS cache, local network cache, and ISP cache.

- If the IP address cannot be found at any of the caches, the browser goes to DNS servers to do a recursive DNS lookup until the IP address is found (this will be covered in another post).

• •Now that we have the IP address of the server, the browser establishes a TCP connection with the server.

• •The browser sends an HTTP request to the server. The request looks like this:

```

𝘎𝘌𝘛 /𝘱𝘩𝘰𝘯𝘦 𝘏𝘛𝘛𝘗/1.1

𝘏𝘰𝘴𝘵: 𝘦𝘹𝘢𝘮𝘱𝘭𝘦.𝘤𝘰𝘮

```

• •The server processes the request and sends back the response. For a successful response (the status code is 200). The HTML response might look like this:

```

𝘏𝘛𝘛𝘗/1.1 200 𝘖𝘒

𝘋𝘢𝘵𝘦: 𝘚𝘶𝘯, 30 𝘑𝘢𝘯 2022 00:01:01 𝘎𝘔𝘛

𝘚𝘦𝘳𝘷𝘦𝘳: 𝘈𝘱𝘢𝘤𝘩𝘦

𝘊𝘰𝘯𝘵𝘦𝘯𝘵-𝘛𝘺𝘱𝘦: 𝘵𝘦𝘹𝘵/𝘩𝘵𝘮𝘭; 𝘤𝘩𝘢𝘳𝘴𝘦𝘵=𝘶𝘵𝘧-8

<!𝘋𝘖𝘊𝘛𝘠𝘗𝘌 𝘩𝘵𝘮𝘭>

<𝘩𝘵𝘮𝘭 𝘭𝘢𝘯𝘨="𝘦𝘯">

𝘏𝘦𝘭𝘭𝘰 𝘸𝘰𝘳𝘭𝘥

</𝘩𝘵𝘮𝘭\>

```

• •The browser renders the HTML content.