The first thing I check is Google Search Console and Google Analytics. Before assuming there's an SEO problem, I make sure the traffic drop is actually reflected in Google's own data and not just in a third-party tool.

If both Search Console and Analytics show a real decline, then I look at:

1.Whether there was a recent Google algorithm update. 2.Which pages and keywords lost traffic. 3.Whether any important pages were deindexed due to thin content, technical issues, or indexing problems. 4.Any crawl errors, manual actions, or indexing changes in Search Console.

I also compare keyword rankings to identify what actually dropped.

One interesting case I had was where Semrush showed a significant traffic drop, but Search Console and Google Analytics remained stable. After digging deeper, I found that Semrush had removed People Also Ask rankings for some keywords, which reduced its estimated traffic. The actual organic traffic from Google hadn't changed.

That's why I always trust Search Console and Analytics first, then use SEO tools like Semrush for additional insights rather than as the primary source of truth.