caddyserver/caddy

Features

• Automated HTTPS Management - Provisioning and renewing TLS certificates automatically for web services to ensure secure encrypted connections without manual intervention.
• Atomic Configuration Swappers - New configurations are validated and provisioned in the background before replacing the active server state to ensure zero-downtime updates.
• HTTP Server Directives - Caddy defines server behavior using directives that accept optional request matchers and subdirectives to filter and process incoming HTTP traffic based on specific criteria.
• Reverse Proxies - Caddy proxies incoming requests to a backend server, optionally using path matchers to route specific traffic while serving other requests as static files.
• Request Matchers - Caddy defines request matchers to limit the scope of directives by using wildcard, path, or named matcher tokens within the configuration file.
• Reverse Proxy Orchestrators - Routing incoming web traffic to backend services while handling load balancing, request modification, and protocol upgrades transparently.
• Automated Certificate Management - Caddy serves all sites over HTTPS automatically by managing certificate issuance, renewal, and HTTP-to-HTTPS redirection for both public domains and local hostnames.
• On-Demand TLS Issuance - Caddy obtains TLS certificates dynamically during the initial handshake for unknown or customer-provided domains without requiring pre-configuration of hostnames.
• Automatic HTTPS Proxies - A network gateway that manages the full lifecycle of TLS certificates by integrating directly with public and private certificate authorities.
• Server Module Managers - Caddy manages server modules by loading, running, and stopping components through a JSON interface that supports atomic, zero-downtime reloads and isolated module lifecycles.
• HTTP Listener Configurations - Caddy customizes HTTP server listener behavior, including custom names, connection timeouts, keepalive settings, proxy trust configurations, and protocol support for specific listener addresses.
• Modular Plugin Architectures - A core runtime that allows developers to extend server functionality by registering custom components with standardized lifecycle and provisioning methods.
• Extensible Web Servers - A modular server platform that handles HTTP traffic, manages TLS certificates automatically, and supports dynamic configuration through a JSON interface.
• Virtual Host Definitions - Caddy defines site addresses to specify hostnames, ports, and schemes, allowing the server to automatically manage certificates and route incoming requests based on host headers.
• Directive-Based Request Pipelines - Incoming HTTP requests traverse a chain of ordered handler modules that process, match, and transform traffic based on defined rules.
• TLS Handshake Orchestrators - The server intercepts incoming connections to dynamically provision certificates or select appropriate security policies during the TLS handshake process.
• TLS Configuration Management - Caddy manages automatic HTTPS certificate issuance, ACME account details, local certificate authority settings, and TLS handshake behavior like SNI defaults and protocol versions.
• Extensible Server Architectures - Building custom server functionality through a modular plugin system that allows developers to inject logic into the request lifecycle.
• Dynamic Configuration APIs - Updating server settings and routing rules in real-time through an API without interrupting active connections or restarting processes.
• JSON-Driven Configuration Schemas - The entire server state is represented as a hierarchical JSON document that defines all modules, routes, and global settings.
• Dynamic Configuration Engines - A control plane that processes and validates server settings in real-time to enable zero-downtime updates and atomic configuration reloads.
• Server Site Blocks - Caddy defines site blocks to configure web servers, using curly braces for multiple sites or optional braces for single-site configurations to manage server settings.
• Admin API Control Planes - A dedicated internal HTTP interface provides secure, authenticated access to manage server state, inspect metrics, and trigger runtime operations.
• Static File Servers - Caddy launches a production-ready static file server with support for directory browsing, template rendering, access logging, and automatic compression of served files.
• Structured Logging - Caddy emits structured log messages from core or plugin code by providing a log level, a message, and strongly-typed fields for efficient, low-overhead diagnostic data collection.
• Guest Module Loaders - Caddy loads and initializes guest modules within a host module by defining raw JSON fields and using context methods to provision and store the resulting module instances.
• Module Registration Interfaces - Caddy allows developers to register custom modules that follow a standardized lifecycle of loading, provisioning, and cleanup to integrate seamlessly with the core server process.
• Certificate Storage Backends - Caddy configures persistent storage backends to share certificates and coordinate management across multiple server instances in a cluster.
• ACME Validation Strategies - Caddy validates domain ownership using HTTP, TLS-ALPN, or DNS challenges to obtain publicly-trusted TLS certificates from ACME-compliant certificate authorities.
• Single Page Application Hosting - Caddy hosts single-page applications by rewriting requests for non-existent files to a central index file, allowing client-side routing to manage the application state.
• Static Asset Serving - Deploying high-performance web servers optimized for delivering static files, directory listings, and compressed content to end users.
• Global Server Settings - Caddy configures global server behavior including debug logging, network port assignments, default bind addresses, directive execution order, storage backends, and administrative API settings.
• Interface-Based Module Registries - Modules implement specific Go interfaces to allow the core system to dynamically load, provision, and manage their lifecycles.
• Certificate Authorities - Caddy defines internal certificate authority parameters, including common names, certificate lifetimes, and maintenance intervals for local HTTPS and ACME server features.
• Global Configuration Options - Caddy sets global configuration options that apply to the entire server instance by defining a special block at the beginning of the configuration file.
• Observability-First Runtimes - A production-ready server environment that provides structured logging, performance profiling, and metrics endpoints for monitoring and diagnostic analysis.
• Module Lifecycle Management - Caddy manages the lifecycle of custom modules by implementing provisioning, validation, and cleanup methods that execute automatically when modules are loaded or discarded by the system.
• Expression-Based Matchers - Caddy evaluates custom boolean logic for request matching using the Common Expression Language to combine multiple criteria flexibly.
• Host Header Matchers - Caddy matches requests based on the Host header field, useful for applying specific logic within site blocks that handle multiple hostnames.
• Directive Execution Orderers - Caddy controls the execution sequence of HTTP handlers by relying on a hard-coded default order or by explicitly overriding the evaluation priority for specific directives.
• Dynamic Configuration Placeholders - Caddy injects dynamic values into configuration arguments using placeholders, which are expanded at runtime based on the request context or specific module data.
• Reusable Configuration Blocks - Caddy defines reusable route blocks to share complex configurations across multiple sites, reducing memory usage and simplifying maintenance for repeated server logic.
• Metrics Collectors - Caddy enables metrics collection for the server to observe request patterns, with options for per-host granularity and automatic discovery of unconfigured hosts.
• Runtime Performance Profilers - Caddy accesses runtime performance profiles including heap, CPU, and goroutine data through the admin interface to diagnose memory leaks, contention, and performance bottlenecks.
• Local Certificate Authorities - Caddy generates and manages local certificate authorities to provide trusted HTTPS for internal hostnames and IP addresses that do not qualify for public certificates.
• Filesystem Request Matchers - Caddy matches requests based on the existence, size, or modification time of files on disk, with support for custom root directories and fallback policies.
• Query Parameter Matchers - Caddy matches requests based on specific query string parameters, supporting exact key matching, wildcard values, and multiple values per key.
• Event-Driven Lifecycle Managers - System components communicate through a centralized event bus that triggers automated actions like certificate renewal or configuration reloads.