Default Combined log format vs a custom one

Default Combined log format vs a custom one

Before you analyze, decide what you log. The choice shapes every later query.

→ Combined Log Format — the Apache/Nginx default. Universal, every tool parses it, but it omits response time and the real client IP behind a proxy.
→ Custom format — add $request_time and $http_x_forwarded_for and suddenly you can answer "is Googlebot getting slow responses" and "what's the true crawler IP behind Cloudflare" — questions Combined simply can't.

⭐ Pick of the week: the foresight tip from Nginx tuning guides — add response time to your log format before you need it; you can't backfill a field you never recorded.

Takeaway: Combined for instant tool compatibility; a custom format when you want crawl latency and true client IP, which you must set up in advance.