What happens when you type a URL into your browser?

URL is composed of 4 parts:

• scheme
• domain
• path
• resource

1. look up ip from domain name system(DNS)

   It has cache. From browser -> OS -> local network -> ISP -> DNS server

2. After find the ip, try to establish tcp connection. (3 way handshake)

3. Browser send the request header to server

4. Server processes request and sends back a response

5. Parse the html , the dom tree and css dom tree will create a render tree, combined with the javascript.

6. The last step is painted.