From OpenLiteSpeed Wiki
- Event-driven architecture with extremely low resource (CPU and RAM) overhead.
- Handles hundreds of thousands of concurrent connections without load spikes.
- WebAdmin GUI with real-time statistics.
- Rewrite engine uses Apache mod_rewrite syntax.
- Worker processes for scalability. Ability to bind certain processes to particular workers.
- High-performance coding using kqueue (FreeBSD and OS X), epoll (Linux), /dev/poll (Solaris), and poll.
- High-performance page caching.
- Support of third-party modules through API (LSIAPI).
- Sendfile() support.
- SPDY/2, 3, and 3.1 support.
- Pipelined requests.
- Gzip compression for reduced bandwidth use.
- Static content up to 5X faster than Apache.
- PHP up to 3x faster than Apache.
- HTTPS up to 4x faster than Apache.
External Applications Support
- Supports PHP, Ruby, Python, Perl, and Java external applications.
- LSAPI, a LiteSpeed-native SAPI, greatly improves PHP, Ruby, and Python speeds.
- Delegates external applications to separate processes, increasing efficiency.
- Buffers requests and responses to external applications to more efficiently serve multiple connections.
- Efficient CGI daemon.
- Compatibility with third party PHP accelerators.
- More efficient communications, controlled number of processes, and less web server resource usage increases scalability of web applications.
- Apache-compatible SSI support.
- SSL support and hardware acceleration.
- Bandwidth and connection throttling.
- IP-based access control.
- Strict HTTP request validation.
- Referer limiting.
- Response rate limiting.
- Anti SSL BEAST and renegotiation attack capabilities.
- Buffer overrun guards.
- Graceful restart feature allows application of configuration changes and upgrades without server downtime.
- Fault tolerance and instant restarting.
- Runs completely in user space. OS reliability is not affected.
Basic HTTP Server Features
- Unlimited concurrent connections.
- Accept-filters and TCP_DEFER_ACCEPT support.
- Chunked transfer encoding.
- Keep-alive connections.
- IPv4 and IPv6.
- Entity tags.
- Multi-range requests.
- Exact/prefix/regex-based matching.
- Unlimited name-based and IP-based virtual hosting.
- Custom error pages.
- Easy virtual host configuration via templates.
- mp4 and flv streaming.
- Easily run multiple versions of PHP on one server.
- IP geolocation.
- Can send logging to logging server.
- Load balancing.
- XML or flat file configuration.
- Can serve as a reverse proxy to accelerate static content delivery, compress throughput, or run security.
- OCSP stapling.
- WebSocket proxy support.