Apache HTTP Server Configuration Cheat Sheet

Updated 2026-05-28

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Apache HTTP Server (httpd) is the world's most widely used open-source web server, powering a significant share of the web since 1995 and continuously updated — Apache 2.4.67 (May 2026) is the current stable release. Its directive-based, modular architecture lets administrators configure everything from static file serving to complex multi-domain hosting with SSL/TLS, reverse proxying, load balancing, and automatic certificate management via ACME (mod_md). Understanding Apache's configuration hierarchy — server config → virtual host → directory → .htaccess — is the single most important mental model for avoiding unexpected behavior in production environments.

What This Cheat Sheet Covers

This topic spans 27 focused tables and 222 indexed concepts, 156 flashcards. Below is a complete table-by-table outline of this topic, spanning foundational concepts through advanced details.

Table 1: Virtual Host ConfigurationTable 2: Core Server DirectivesTable 3: Directory and Access ControlTable 4: .htaccess ConfigurationTable 5: URL Rewriting (mod_rewrite)Table 6: Reverse Proxy and Load BalancingTable 7: SSL/TLS Configuration (mod_ssl)Table 8: MPM (Multi-Processing Module) ConfigurationTable 9: HTTP Connection ManagementTable 10: Logging ConfigurationTable 11: Performance and CachingTable 12: Compression (moddeflate and modbrotli)Table 13: Authentication and AuthorizationTable 14: Security HardeningTable 15: Conditional ConfigurationTable 16: HTTP Headers (mod_headers)Table 17: Environment VariablesTable 18: Redirects and URL ManipulationTable 19: mod_remoteip (Client IP Handling)Table 20: Advanced Proxy FeaturesTable 21: HTTP/2 Configuration (mod_http2)Table 22: Automatic TLS with mod_md (ACME)Table 23: WebSocket Proxy SupportTable 24: CGI and Script ExecutionTable 25: mod_macro (Configuration Macros)Table 26: Content NegotiationTable 27: Legacy Access Control (Apache 2.2 Syntax)

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Table 1: Virtual Host Configuration

Name-based virtual hosting is the standard approach: a single IP serves many domains, with Apache routing by the Host header. IP-based virtual hosting is reserved for rare cases where TLS SNI is unavailable. Every virtual host should have its own ErrorLog and CustomLog to keep troubleshooting clean.

Directive	Example	Description
VirtualHost	`<code><VirtualHost :443></code>` `ServerName example.com` </VirtualHost> `\| Defines a named or IP-based virtual host* container;` *:port` matches all IPs on that port for name-based hosting. \|
ServerName	`ServerName www.example.com`	Canonical hostname used to identify the virtual host; essential for name-based routing and self-referential URL generation.
ServerAlias	`ServerAlias example.com *.example.com`	Alternate hostnames for the virtual host; wildcard patterns match multiple subdomains within one block.
DocumentRoot	`DocumentRoot "/var/www/html"`	Root filesystem directory from which Apache serves files; must exist and be readable by the Apache process.
ServerAdmin	`ServerAdmin admin@example.com`	Administrator email shown on server-generated error pages.
ErrorLog	`ErrorLog "/var/log/httpd/error_log"`	Error log file for this virtual host; use per-vhost paths for isolated troubleshooting.
CustomLog	`CustomLog "/var/log/httpd/access_log" combined`	Access log path and format; `combined` includes referrer and User-Agent for detailed analytics.
UseCanonicalName	`UseCanonicalName Off`	Controls whether self-referential URLs use ServerName (`On`) or the client's Host header (`Off`); `Off` is the default and correct for name-based virtual hosting.
NameVirtualHost (legacy)	`NameVirtualHost *:80`	• Apache 2.2 directive to designate an IP:port for name-based hosting • obsolete in Apache 2.4 where name-based virtual hosting is automatic.

Table 2: Core Server Directives

These directives form the skeleton of httpd.conf and apply globally before any virtual host or directory context. Getting ServerRoot, Listen, and module loading right is a prerequisite for everything else.

Directive	Example	Description
Listen	`Listen 80` `Listen 192.168.1.10:443`	• Tells Apache which IP addresses and ports to bind to • both `address:port` and port-only forms are supported

The rest of this section is part of the full cheat sheet

Table 3: Directory and Access Control

Container directives (<Directory>, <Files>, <Location>) are the fundamental scoping mechanism in Apache. They are evaluated in a specific order — filesystem containers before URL containers — and the most specific match wins.

Directive	Example	Description
Directory	`<code><Directory "/var/www/html"></code>` `Require all granted` </Directory>` \| Encloses directives applying to a specific filesystem directory and its subdirectories; fundamental for path-based access control. \|

The rest of this section is part of the full cheat sheet

Table 4: .htaccess Configuration

.htaccess files enable per-directory configuration without restarting the server, at the cost of a filesystem lookup on every request. Setting AllowOverride None globally and enabling it only where needed is the recommended production pattern.

Directive	Example	Description
RewriteEngine	`RewriteEngine On`	• Enables the rewrite engine for the current scope • must be `On` before any `RewriteRule` takes effect

The rest of this section is part of the full cheat sheet

Table 1: Virtual Host Configuration

Directive	Example	Description
VirtualHost	`<code><VirtualHost :443></code>` `ServerName example.com` </VirtualHost> `\| Defines a named or IP-based virtual host* container;` *:port` matches all IPs on that port for name-based hosting. \|
ServerName	`ServerName www.example.com`	Canonical hostname used to identify the virtual host; essential for name-based routing and self-referential URL generation.
ServerAlias	`ServerAlias example.com *.example.com`	Alternate hostnames for the virtual host; wildcard patterns match multiple subdomains within one block.
DocumentRoot	`DocumentRoot "/var/www/html"`	Root filesystem directory from which Apache serves files; must exist and be readable by the Apache process.
ServerAdmin	`ServerAdmin admin@example.com`	Administrator email shown on server-generated error pages.
ErrorLog	`ErrorLog "/var/log/httpd/error_log"`	Error log file for this virtual host; use per-vhost paths for isolated troubleshooting.
CustomLog	`CustomLog "/var/log/httpd/access_log" combined`	Access log path and format; `combined` includes referrer and User-Agent for detailed analytics.
UseCanonicalName	`UseCanonicalName Off`	Controls whether self-referential URLs use ServerName (`On`) or the client's Host header (`Off`); `Off` is the default and correct for name-based virtual hosting.
NameVirtualHost (legacy)	`NameVirtualHost *:80`	• Apache 2.2 directive to designate an IP:port for name-based hosting • obsolete in Apache 2.4 where name-based virtual hosting is automatic.

Table 2: Core Server Directives

Directive	Example	Description
Listen	`Listen 80` `Listen 192.168.1.10:443`	• Tells Apache which IP addresses and ports to bind to • both `address:port` and port-only forms are supported

Table 3: Directory and Access Control

Directive	Example	Description
Directory	`<code><Directory "/var/www/html"></code>` `Require all granted` </Directory>` \| Encloses directives applying to a specific filesystem directory and its subdirectories; fundamental for path-based access control. \|

Table 4: .htaccess Configuration

Directive	Example	Description
RewriteEngine	`RewriteEngine On`	• Enables the rewrite engine for the current scope • must be `On` before any `RewriteRule` takes effect