Here is a list of all related documentation pages:

Alignment package
CI instructions
Code Of Conduct
The ACTS project
Code guidelines
What is clang-tidy?
Contribution guidelines
How do I build the documentation?
Documentation Markdown Cheatsheet
What is physmon?
Profiling
How to make a release
What are ROOT hash checks?
run_formatting
Unit definitions and conversions
Event data
Measurements
Track parametrization
Particle hypothesis
tracks
Geometry identifier
index
Tracking geometry building
layerless
Geometry building
Layer classes
legacy
Volume classes
Detector material description
Surface classes
How-to guides for Core components
material_mapping
magnetic_field
material
Grid and axis
Miscellaneous
Logging
propagation
Track reconstruction
Pattern recognition
seeding
track_finding
clustering
Preprocessing of event data
spacepoint_formation
Track Fitting
vertexing
3D Visualization
Visualization
SVG for 2D visualization
Alignment prototype
Walkthrough of the OpenDataDetector full chain example
Add a new algorithm
Generate a configuration file for the smearing digitizer
GSF Debugger
How-to guides for the Examples
Fatras
Getting started
Glossary
DD4hep plugin
exatrkx
Geant4 plugin
JSON
Machine learning algorithms
Tracking in a nutshell
How to add a white paper
Full chain examples for development and (manual) tests
GSF Debugger
FAst TRAck Simulation package
Exa.TrkX Plugin
Acts Common Tracking Software
Small test data files
Example Acts downstream project
Example Acts downstream project
Integration tests
Build Recipe for ActSVG
Build Recipe for algebra-plugins
Build Recipe for covfie
Build Recipe for detray
Build Recipe for dfelibs
Build Recipe for GeoModel
Third party software
Build Recipe for traccc
Build Recipe for VecMem
Changelog
LICENSE
Dr. Fred Edison's incredible useful C++14 libraries
Accessing DetectorIDs from Python
LDMX Detectors
Generating the Documentation
ECal Data Files
Ecal
Abandoned
Framework
Example Configuration Files
Hcal
MagFieldMap
Packing
SimCore
HLS Arbitrary Precision Types
Tracking
README
Software Emulation of Trigger Algorithms
ECal HLS Algorithm Implementation
Placeholder for HLS algorithms
HLS Algorithm Implementation
Trigger Scintillator HLS Algorithm Implementation
Trigger
ruckus
TrigScint
Validation