Both generations evaluate ModSecurity rules, but they attach to web servers differently and should not be treated as interchangeable binaries.
| ModSecurity 2.x | libmodsecurity 3.x | |
|---|---|---|
| Architecture | Embedded web-server module | Standalone engine library plus connector |
| Common fit | Apache and IIS | Nginx and connector-based integrations |
| Apache maturity | Long-established | Connector-dependent |
| Nginx fit | Older approaches were indirect | Native architecture for the Nginx connector |
| Configuration | Broad 2.x feature history | High compatibility, with some behavioral differences |
Practical choice
Use the supported package designed for your web server. For Apache or IIS, that is commonly ModSecurity 2.x. For Nginx, use libmodsecurity 3 and the Nginx connector. Test your actual rules and audit logging whenever migrating between generations.