A 408 usually reflects performance or network issues: the server gave up waiting. For occasional users this is a transient glitch, but if Googlebot repeatedly hits timeouts, it reads the site as slow or unreliable and can reduce crawl frequency.
That makes 408 partly a speed and stability signal. Persistent timeouts hurt both user experience and crawl efficiency, and slow responses relate to Core Web Vitals and overall page experience.
The fix lives in infrastructure: faster server response times, sensible timeout settings, caching, and enough capacity to handle traffic and crawl load. Recurring 408s alongside 503 responses are a sign the server is under-resourced.
This is a technical SEO topic I handle for clients:
Technical SEO →