Lifecycle of a URL access on a Browser

Step 1

• DNS lookup
  • Browser cache
  • OS cache
  • Router cache
  • ISP DNS lookup

Step 2

• Connection setup
  • 3 phase TCP connection

Step 3

• Browser sends HTTP request
  • GET
  • POST (for auth and form submission)

Step 4

• Server handles the request and prepares a response.
  • Server could be a web server (Apache, IIS)
  • Handler parses the request header
  • Handler can be coded on ASP, PHP etc.

Step 5

• Server responds with HTTP header having status code

Step 6

• Browser gets HTML data
• It renders tags
• Fetches images, CSS using GET (usually cached)

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