Regular expressions in filtering
DNS Management
Regular expressions (regex) provide a powerful pattern-matching tool within Pi-hole, enabling sophisticated domain filtering that goes beyond simple exact matches. Where standard blocklist entries match specific domains, regex rules can match multiple domains based on patterns.
Consider these common Pi-hole regex patterns:
^ads\..* # Blocks all domains starting with "ads."
.*\.example\.com # Blocks all subdomains of example.com
^(.+[-_.])??ads[.-].*$ # More comprehensive ad domain blocking
Managing Regex in Pi-hole:
- Through the web interface:
- Navigate to "Blacklist" under "Group Management"
- Select "Add regex filter" option
- Enter your pattern
- Save changes
Common Use Cases:
- Block all subdomains of a problematic domain
- Match common advertising domain patterns
- Filter domains containing specific keywords
- Block patterns that rotate domains (e.g., ad1.site.com, ad2.site.com)
A Word of Caution: Regex filters are powerful but require careful testing. An overly broad pattern might accidentally block legitimate domains. Always verify regex rules in the Query Log before implementing permanently.
Best Practice: Start with simple patterns and test thoroughly. Document your regex rules with comments explaining their purpose, as patterns can be difficult to decipher later.
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