Lighttpd

lighttpd is an open-source HTTP server designed for speed-critical and resource-constrained environments. It focuses on a small memory footprint and event-driven request handling to support high concurrency with low CPU and memory usage.

Key Features

• Event-driven architecture with support for efficient notification mechanisms (select/poll/kqueue/epoll) for high concurrency and low resource use.
• Modular feature set including FastCGI, SCGI and CGI integrations for serving dynamic applications and PHP support tuned for FastCGI.
• Protocol support for HTTP/1.0, HTTP/1.1 and HTTP/2, plus HTTPS via multiple TLS libraries.
• Built-in reverse-proxy, load-balancing for FastCGI/SCGI, websocket tunneling and streaming proxy capabilities.
• Common web server features: virtual hosting, directory listings, URL rewriting, conditional redirects, range requests, and on-the-fly output compression.
• Security and reliability features: chroot/setuid/setgid support, authentication (basic/digest/LDAP), and configurable TLS backends.

Use Cases

• Serving static assets or acting as an offload front-end to application servers where low memory and high throughput are required.
• Hosting PHP or other dynamic apps via FastCGI/SCGI with efficient process management and load distribution.
• Lightweight web server for embedded devices, appliance interfaces, or small servers where minimal resource usage is important.

Limitations and Considerations

• Does not provide native HTTP/3 support; HTTP/2 is supported but newer QUIC/HTTP/3 features are not available in the 1.4 branch.
• Smaller module/ecosystem footprint compared to larger servers (e.g., Apache or Nginx), which can limit plugin availability for niche integrations.
• Historically there have been security issues reported in some embedded firmware usages; administrators should track updates and apply patches promptly.

In summary, lighttpd is a purpose-built, low-footprint web server suited for high-concurrency, performance-sensitive deployments where resource efficiency is a priority. It provides a focused set of protocols and modules for common web workloads while trading broader ecosystem coverage for a smaller runtime and lower overhead.