Overview

Relevant source files

Purpose and Scope

Fastfetch is a cross-platform system information fetching tool written primarily in C11 (with optional C++17 components). It detects and displays hardware and software information through a modular, extensible architecture that supports 70+ detection modules across 9+ operating systems. The project emphasizes performance, configurability, and platform abstraction.

This page provides a high-level architectural overview of the entire fastfetch codebase. For specific topics, see:

Build configuration and feature flags: Build System and Feature Configuration
Configuration file formats and parsing: Configuration Parsing System
Individual detection modules: Detection Subsystems
Logo rendering and display: Logo Rendering System

Sources: README.md1-16 CMakeLists.txt1-10

Architecture Philosophy

Fastfetch follows a layered architecture with clear separation of concerns:

Platform Abstraction: Common detection interfaces implemented with platform-specific backends
Module Registry: Compile-time registration of detection modules organized alphabetically (A-Z)
Configuration Cascade: Defaults → JSONC/JSON5 config files → CLI arguments
Single-Pass Execution: Each module runs once during program execution (unless dynamic refresh is enabled)
Zero External Dependencies: Core functionality works without optional libraries

The design prioritizes compile-time polymorphism over runtime dispatch, using function pointers in FFModuleBaseInfo structures registered at compile time rather than virtual function tables or dynamic plugin loading.

Sources: src/fastfetch.h1-48 src/modules/modules.c1-184

System Architecture

The following diagram illustrates the major system components and their relationships using actual code entities:

Diagram: Fastfetch System Architecture with Code Entities

This architecture enables:

O(1) module lookup: The A-Z bucketing in ffModuleInfos provides constant-time initial lookup
Compile-time registration: All modules are statically linked into the binary
Platform abstraction: Detection functions call platform-specific implementations via function pointers
Single global state: The instance global variable (defined in src/common/impl/init.c) provides access to configuration and state throughout the codebase

Sources: src/fastfetch.h23-48 src/fastfetch.c1-17 src/modules/modules.c1-184 src/flashfetch.c1-148

Execution Flow

Diagram: Fastfetch Execution Flow

Key execution characteristics:

Phase	Function	Source File	Purpose
Initialization	`ffInitInstance()`	src/common/impl/init.c	Set up global `instance` variable
Argument Parsing	`parseCommand()`	src/fastfetch.c590-743	Process CLI flags and commands
Config Loading	`parseJsoncFile()`	src/fastfetch.c383-433	Parse JSONC/JSON5 configuration
Validation	`ffOptionsParseLogoJsonConfig()`	src/options/logo.c	Validate against JSON schema
Platform Init	`ffStart()`	src/common/impl/init.c	Detect OS, terminal, initialize FFPlatform
Logo Rendering	`ffLogoPrint()`	src/logo/logo.c	Display ASCII art or image
Module Execution	`run()`	src/fastfetch.c744-893	Iterate through modules
Cleanup	`ffDestroyInstance()`	src/common/impl/init.c	Free resources

Sources: src/fastfetch.c1-1000 src/common/impl/init.c

Core Data Structures

FFinstance: Global State Container

The entire application state is contained in the instance global variable:

FFconfig contains three major option groups:

Field	Type	Purpose	Default Config File Location
`logo`	`FFOptionsLogo`	Logo type, source, colors, padding	src/options/logo.c
`display`	`FFOptionsDisplay`	Output formatting, colors, units, bars	src/options/display.c
`general`	`FFOptionsGeneral`	Platform-specific settings, timeouts	src/options/general.c

FFstate tracks runtime information:

Field	Type	Purpose
`logoWidth`	`uint32_t`	Width of printed logo in characters
`logoHeight`	`uint32_t`	Height of printed logo in lines
`keysHeight`	`uint32_t`	Number of module outputs printed
`terminalLightTheme`	`bool`	Whether terminal uses light theme
`platform`	`FFPlatform`	Platform-specific paths and information
`dynamicInterval`	`uint32_t`	Milliseconds between refreshes (0 = disabled)

Sources: src/fastfetch.h23-48 src/options/logo.h src/options/display.h src/options/general.h

FFModuleBaseInfo: Module Interface

Every detection module implements the FFModuleBaseInfo interface:

Modules are registered in ffModuleInfos[26] arrays indexed by first letter (A-Z). Example from src/modules/modules.c20-31:

Sources: src/modules/modules.h1-77 src/modules/modules.c1-184

Module System Architecture

Fastfetch implements a compile-time module registry with 70+ modules organized alphabetically. Each module follows a consistent pattern:

Diagram: Module System Architecture (CPU Module Example)

Module categories by functionality:

Category	Modules	Example Files
Hardware	CPU, GPU, Memory, Disk, Battery, Monitor	src/modules/cpu/ src/modules/gpu/
Software	OS, Kernel, Packages, Shell, Terminal, DE, WM	src/modules/os/ src/modules/packages/
Network	LocalIP, PublicIP, WiFi, DNS	src/modules/localip/ src/modules/wifi/
Media	Player, Media (song info)	src/modules/player/ src/modules/media/
System State	Uptime, Processes, Users, DateTime	src/modules/uptime/ src/modules/processes/
Presentation	Title, Separator, Break, Colors, Custom	src/modules/title/ src/modules/colors/

Sources: src/modules/modules.c1-184 src/modules/modules.h1-77 src/modules/cpu/cpu.c src/detection/cpu/cpu.c

Platform Abstraction Pattern

Fastfetch achieves cross-platform support through a three-tier abstraction:

Diagram: Three-Tier Platform Abstraction Pattern

Platform-specific file naming convention:

Pattern	Example	Platform
`*_linux.c`	`cpu_linux.c`	Linux (GNU/Linux)
`*_windows.c`	`cpu_windows.c`	Windows
`*_apple.c`	`cpu_apple.c`	macOS (C code)
`*_apple.m`	`disk_apple.m`	macOS (Objective-C)
`*_bsd.c`	`cpu_bsd.c`	FreeBSD, MidnightBSD, DragonFly
`*_obsd.c`	`cpu_obsd.c`	OpenBSD
`*_nbsd.c`	`cpu_nbsd.c`	NetBSD
`*_android.c`	`os_android.c`	Android
`*_nosupport.c`	`btrfs_nosupport.c`	Platform doesn't support feature

Sources: CMakeLists.txt515-845 src/detection/cpu/cpu_linux.c src/detection/cpu/cpu_windows.c src/detection/cpu/cpu_apple.c

Platform Support Matrix

Fastfetch supports 9+ operating systems with varying feature completeness:

Platform	Detected In	Build Configuration	Key Detection Files
Linux	CMakeLists.txt28-29	`LINUX=TRUE`	src/common/impl/FFPlatform_unix.c
Windows	CMakeLists.txt48	`WIN32`	src/common/impl/FFPlatform_windows.c
macOS	CMakeLists.txt48	`APPLE`	src/common/impl/FFPlatform_unix.c
FreeBSD	CMakeLists.txt30-31	`FreeBSD=TRUE`	src/common/impl/FFPlatform_unix.c
OpenBSD	CMakeLists.txt32-33	`OpenBSD=TRUE`	src/common/impl/FFPlatform_unix.c
NetBSD	CMakeLists.txt37-38	`NetBSD=TRUE`	src/common/impl/FFPlatform_unix.c
DragonFly	CMakeLists.txt39-41	`DragonFly=TRUE`	src/common/impl/FFPlatform_unix.c
Android	CMakeLists.txt26-27	`ANDROID`	src/common/impl/FFPlatform_unix.c
SunOS	CMakeLists.txt42-43	`SunOS=TRUE`	src/common/impl/FFPlatform_unix.c
Haiku	CMakeLists.txt44-45	`Haiku=TRUE`	src/common/impl/FFPlatform_unix.c
GNU/Hurd	CMakeLists.txt46-47	`GNU=TRUE`	src/common/impl/FFPlatform_unix.c

Architecture support includes: x86_64, i686, aarch64, armv7l, armv6l, riscv64, ppc64le, s390x.

Sources: CMakeLists.txt24-50 README.md16 .github/workflows/ci.yml64-342

Key Capabilities

1. Configuration System

Three formats: JSON (strict), JSONC (with comments), JSON5 (relaxed syntax)
Cascade: CLI flags override config file values, which override defaults
Schema validation: Against doc/json_schema.json
Multiple search paths: ~/.config/fastfetch/, data directories, executable path

2. Module System

70+ modules: Hardware detection, software information, network status, media playback
A-Z registry: Constant-time lookup by module name first letter
Format strings: Customizable output with placeholders like {name}, {cores}, {freq}
JSON output: Structured data export for scripting

3. Logo System

Built-in logos: 500+ ASCII logos in src/logo/builtin.c13-21000
Image protocols: Sixel, Kitty, iTerm, Chafa via ImageMagick
Custom logos: Load from file or auto-detect by OS
Color customization: 9 color slots configurable per logo

4. Platform Abstraction

Consistent API: Same detection functions across platforms
Native system calls: /proc, sysfs (Linux); Registry, WMI (Windows); sysctl, IOKit (macOS)
Graceful degradation: Features unavailable on platform return empty results

5. Build System

CMake: Cross-platform build configuration
40+ feature flags: ENABLE_VULKAN, ENABLE_WAYLAND, ENABLE_IMAGEMAGICK7, etc.
Conditional compilation: Platform-specific code included only when building for that platform
Static and dynamic linking: Controlled via BINARY_LINK_TYPE

Sources: src/fastfetch.c383-569 src/logo/builtin.c1-21000 CMakeLists.txt67-128

Foundation Libraries

Fastfetch relies on two core utility libraries:

FFstrbuf: Dynamic Strings

File: src/common/impl/FFstrbuf.c
80+ operations: Append, trim, search, replace, substring, format
Automatic growth: Realloc on demand with capacity tracking
String interning: Pointer equality for common strings
Usage: All string manipulation throughout codebase

FFlist: Dynamic Arrays

File: src/common/impl/FFlist.c
Generic container: Stores any fixed-size element type
Automatic growth: Exponential capacity increase
Type safety: Macro-based type wrappers
Usage: Collecting detection results (GPUs, disks, network interfaces)

Both types use RAII-style cleanup with FF_AUTO_DESTROY macros.

Sources: src/common/FFstrbuf.h src/common/FFlist.h src/common/impl/FFstrbuf.c src/common/impl/FFlist.c

For deeper exploration of specific subsystems:

Installation and building: Installation and Quick Start
Configuration file syntax: Configuration Overview, Configuration Parsing System
CMake options and feature flags: Build System and Feature Configuration
Module implementation patterns: Module System Architecture
Detection layer details: Detection Subsystems
Output formatting and display: Output and Presentation Systems
Core utility APIs: Foundation Libraries
Contributing and testing: Development and Deployment

Sources: README.md1-342 Wiki Table of Contents

Overview

Relevant source files

Purpose and Scope

This page provides a high-level architectural overview of the entire fastfetch codebase. For specific topics, see:

Build configuration and feature flags: Build System and Feature Configuration
Configuration file formats and parsing: Configuration Parsing System
Individual detection modules: Detection Subsystems
Logo rendering and display: Logo Rendering System

Sources: README.md1-16 CMakeLists.txt1-10

Architecture Philosophy

Fastfetch follows a layered architecture with clear separation of concerns:

Platform Abstraction: Common detection interfaces implemented with platform-specific backends
Module Registry: Compile-time registration of detection modules organized alphabetically (A-Z)
Configuration Cascade: Defaults → JSONC/JSON5 config files → CLI arguments
Single-Pass Execution: Each module runs once during program execution (unless dynamic refresh is enabled)
Zero External Dependencies: Core functionality works without optional libraries

Sources: src/fastfetch.h1-48 src/modules/modules.c1-184

System Architecture

The following diagram illustrates the major system components and their relationships using actual code entities:

Diagram: Fastfetch System Architecture with Code Entities

This architecture enables:

O(1) module lookup: The A-Z bucketing in ffModuleInfos provides constant-time initial lookup
Compile-time registration: All modules are statically linked into the binary
Platform abstraction: Detection functions call platform-specific implementations via function pointers
Single global state: The instance global variable (defined in src/common/impl/init.c) provides access to configuration and state throughout the codebase

Sources: src/fastfetch.h23-48 src/fastfetch.c1-17 src/modules/modules.c1-184 src/flashfetch.c1-148

Execution Flow

Diagram: Fastfetch Execution Flow

Key execution characteristics:

Phase	Function	Source File	Purpose
Initialization	`ffInitInstance()`	src/common/impl/init.c	Set up global `instance` variable
Argument Parsing	`parseCommand()`	src/fastfetch.c590-743	Process CLI flags and commands
Config Loading	`parseJsoncFile()`	src/fastfetch.c383-433	Parse JSONC/JSON5 configuration
Validation	`ffOptionsParseLogoJsonConfig()`	src/options/logo.c	Validate against JSON schema
Platform Init	`ffStart()`	src/common/impl/init.c	Detect OS, terminal, initialize FFPlatform
Logo Rendering	`ffLogoPrint()`	src/logo/logo.c	Display ASCII art or image
Module Execution	`run()`	src/fastfetch.c744-893	Iterate through modules
Cleanup	`ffDestroyInstance()`	src/common/impl/init.c	Free resources

Sources: src/fastfetch.c1-1000 src/common/impl/init.c

Core Data Structures

FFinstance: Global State Container

The entire application state is contained in the instance global variable:

FFconfig contains three major option groups:

Field	Type	Purpose	Default Config File Location
`logo`	`FFOptionsLogo`	Logo type, source, colors, padding	src/options/logo.c
`display`	`FFOptionsDisplay`	Output formatting, colors, units, bars	src/options/display.c
`general`	`FFOptionsGeneral`	Platform-specific settings, timeouts	src/options/general.c

FFstate tracks runtime information:

Field	Type	Purpose
`logoWidth`	`uint32_t`	Width of printed logo in characters
`logoHeight`	`uint32_t`	Height of printed logo in lines
`keysHeight`	`uint32_t`	Number of module outputs printed
`terminalLightTheme`	`bool`	Whether terminal uses light theme
`platform`	`FFPlatform`	Platform-specific paths and information
`dynamicInterval`	`uint32_t`	Milliseconds between refreshes (0 = disabled)

Sources: src/fastfetch.h23-48 src/options/logo.h src/options/display.h src/options/general.h

FFModuleBaseInfo: Module Interface

Every detection module implements the FFModuleBaseInfo interface:

Modules are registered in ffModuleInfos[26] arrays indexed by first letter (A-Z). Example from src/modules/modules.c20-31:

Sources: src/modules/modules.h1-77 src/modules/modules.c1-184

Module System Architecture

Fastfetch implements a compile-time module registry with 70+ modules organized alphabetically. Each module follows a consistent pattern:

Diagram: Module System Architecture (CPU Module Example)

Module categories by functionality:

Category	Modules	Example Files
Hardware	CPU, GPU, Memory, Disk, Battery, Monitor	src/modules/cpu/ src/modules/gpu/
Software	OS, Kernel, Packages, Shell, Terminal, DE, WM	src/modules/os/ src/modules/packages/
Network	LocalIP, PublicIP, WiFi, DNS	src/modules/localip/ src/modules/wifi/
Media	Player, Media (song info)	src/modules/player/ src/modules/media/
System State	Uptime, Processes, Users, DateTime	src/modules/uptime/ src/modules/processes/
Presentation	Title, Separator, Break, Colors, Custom	src/modules/title/ src/modules/colors/

Sources: src/modules/modules.c1-184 src/modules/modules.h1-77 src/modules/cpu/cpu.c src/detection/cpu/cpu.c

Platform Abstraction Pattern

Fastfetch achieves cross-platform support through a three-tier abstraction:

Diagram: Three-Tier Platform Abstraction Pattern

Platform-specific file naming convention:

Pattern	Example	Platform
`*_linux.c`	`cpu_linux.c`	Linux (GNU/Linux)
`*_windows.c`	`cpu_windows.c`	Windows
`*_apple.c`	`cpu_apple.c`	macOS (C code)
`*_apple.m`	`disk_apple.m`	macOS (Objective-C)
`*_bsd.c`	`cpu_bsd.c`	FreeBSD, MidnightBSD, DragonFly
`*_obsd.c`	`cpu_obsd.c`	OpenBSD
`*_nbsd.c`	`cpu_nbsd.c`	NetBSD
`*_android.c`	`os_android.c`	Android
`*_nosupport.c`	`btrfs_nosupport.c`	Platform doesn't support feature

Sources: CMakeLists.txt515-845 src/detection/cpu/cpu_linux.c src/detection/cpu/cpu_windows.c src/detection/cpu/cpu_apple.c

Platform Support Matrix

Fastfetch supports 9+ operating systems with varying feature completeness:

Platform	Detected In	Build Configuration	Key Detection Files
Linux	CMakeLists.txt28-29	`LINUX=TRUE`	src/common/impl/FFPlatform_unix.c
Windows	CMakeLists.txt48	`WIN32`	src/common/impl/FFPlatform_windows.c
macOS	CMakeLists.txt48	`APPLE`	src/common/impl/FFPlatform_unix.c
FreeBSD	CMakeLists.txt30-31	`FreeBSD=TRUE`	src/common/impl/FFPlatform_unix.c
OpenBSD	CMakeLists.txt32-33	`OpenBSD=TRUE`	src/common/impl/FFPlatform_unix.c
NetBSD	CMakeLists.txt37-38	`NetBSD=TRUE`	src/common/impl/FFPlatform_unix.c
DragonFly	CMakeLists.txt39-41	`DragonFly=TRUE`	src/common/impl/FFPlatform_unix.c
Android	CMakeLists.txt26-27	`ANDROID`	src/common/impl/FFPlatform_unix.c
SunOS	CMakeLists.txt42-43	`SunOS=TRUE`	src/common/impl/FFPlatform_unix.c
Haiku	CMakeLists.txt44-45	`Haiku=TRUE`	src/common/impl/FFPlatform_unix.c
GNU/Hurd	CMakeLists.txt46-47	`GNU=TRUE`	src/common/impl/FFPlatform_unix.c

Architecture support includes: x86_64, i686, aarch64, armv7l, armv6l, riscv64, ppc64le, s390x.

Sources: CMakeLists.txt24-50 README.md16 .github/workflows/ci.yml64-342

Key Capabilities

1. Configuration System

Three formats: JSON (strict), JSONC (with comments), JSON5 (relaxed syntax)
Cascade: CLI flags override config file values, which override defaults
Schema validation: Against doc/json_schema.json
Multiple search paths: ~/.config/fastfetch/, data directories, executable path

2. Module System

70+ modules: Hardware detection, software information, network status, media playback
A-Z registry: Constant-time lookup by module name first letter
Format strings: Customizable output with placeholders like {name}, {cores}, {freq}
JSON output: Structured data export for scripting

3. Logo System

Built-in logos: 500+ ASCII logos in src/logo/builtin.c13-21000
Image protocols: Sixel, Kitty, iTerm, Chafa via ImageMagick
Custom logos: Load from file or auto-detect by OS
Color customization: 9 color slots configurable per logo

4. Platform Abstraction

Consistent API: Same detection functions across platforms
Native system calls: /proc, sysfs (Linux); Registry, WMI (Windows); sysctl, IOKit (macOS)
Graceful degradation: Features unavailable on platform return empty results

5. Build System

CMake: Cross-platform build configuration
40+ feature flags: ENABLE_VULKAN, ENABLE_WAYLAND, ENABLE_IMAGEMAGICK7, etc.
Conditional compilation: Platform-specific code included only when building for that platform
Static and dynamic linking: Controlled via BINARY_LINK_TYPE

Sources: src/fastfetch.c383-569 src/logo/builtin.c1-21000 CMakeLists.txt67-128

Foundation Libraries

Fastfetch relies on two core utility libraries:

FFstrbuf: Dynamic Strings

File: src/common/impl/FFstrbuf.c
80+ operations: Append, trim, search, replace, substring, format
Automatic growth: Realloc on demand with capacity tracking
String interning: Pointer equality for common strings
Usage: All string manipulation throughout codebase

FFlist: Dynamic Arrays

File: src/common/impl/FFlist.c
Generic container: Stores any fixed-size element type
Automatic growth: Exponential capacity increase
Type safety: Macro-based type wrappers
Usage: Collecting detection results (GPUs, disks, network interfaces)

Both types use RAII-style cleanup with FF_AUTO_DESTROY macros.

Sources: src/common/FFstrbuf.h src/common/FFlist.h src/common/impl/FFstrbuf.c src/common/impl/FFlist.c

For deeper exploration of specific subsystems:

Installation and building: Installation and Quick Start
Configuration file syntax: Configuration Overview, Configuration Parsing System
CMake options and feature flags: Build System and Feature Configuration
Module implementation patterns: Module System Architecture
Detection layer details: Detection Subsystems
Output formatting and display: Output and Presentation Systems
Core utility APIs: Foundation Libraries
Contributing and testing: Development and Deployment

Sources: README.md1-342 Wiki Table of Contents

Overview

Purpose and Scope

Architecture Philosophy

System Architecture

Execution Flow

Core Data Structures

FFinstance: Global State Container

FFModuleBaseInfo: Module Interface

Module System Architecture

Platform Abstraction Pattern

Platform Support Matrix

Key Capabilities

1. Configuration System

2. Module System

3. Logo System

4. Platform Abstraction

5. Build System

Foundation Libraries

FFstrbuf: Dynamic Strings

FFlist: Dynamic Arrays

Related Documentation

On this page

Overview

Purpose and Scope

Architecture Philosophy

System Architecture

Execution Flow

Core Data Structures

FFinstance: Global State Container

FFModuleBaseInfo: Module Interface

Module System Architecture

Platform Abstraction Pattern

Platform Support Matrix

Key Capabilities

1. Configuration System

2. Module System

3. Logo System

4. Platform Abstraction

5. Build System

Foundation Libraries

FFstrbuf: Dynamic Strings

FFlist: Dynamic Arrays

Related Documentation

On this page