How Important Is SEO During Website Development?

Many developers say SEO can be added later, while others recommend building it into the website from day one. For those who have launched new websites, how much attention did you give to SEO during development? Did it have a noticeable impact on rankings and traffic after launch? I would love to know which SEO elements are most important to address before a site goes live.

Building a site without SEO in mind is just creating technical debt. Things like page speed, mobile responsiveness, and clean header hierarchies are inherently tied to both UX and search performance. When we built our latest platform, we mapped out the redirect strategy and XML sitemaps before even touching the final code. We also did some heavy competitor research on search engine optimization sydney to see how local agencies structured their high-ranking landing pages. The effort paid off because we started ranking for our core long-tail keywords almost immediately after the launch.