Robots.txt is a small text file with potentially large consequences. One broad rule can affect how crawlers access a large part of a website, so the safest approach is to keep rules narrow, intentional and easy to understand.
What robots.txt does
Robots.txt communicates crawler instructions to compliant automated agents. It can help reduce unnecessary requests to sections that do not need crawling. It is not a password system and should never be treated as protection for confidential files.
Be careful with broad rules
A rule that blocks the entire site can be useful in a private environment but harmful when it reaches production. Before adding a rule, identify the exact path and the reason for blocking it.
Keep private data private
If a document should not be publicly accessible, use authentication or server permissions. Robots.txt itself is public and cannot prevent someone from requesting a known URL.
Pair it with a sitemap
Keep the crawler instructions and your public sitemap logically consistent. The Robots.txt & XML Sitemap Generator can help create both, but the output still needs human review.
Test after migrations
Domain changes, HTTPS migrations and redesigns are common times for robots mistakes. A staging rule can accidentally reach production, or an old rule can survive after a URL structure changes. Open the live robots.txt after every major migration.
Conclusion
Use robots.txt for crawler guidance, not security. Keep it simple, review every broad rule, and test the actual public file after important site changes.