Prison Architect: Best preferences.txt for UI Scaling Fix

The objective is to manually define the UI Scale ($S_{ui}$) and coordinate it with your native resolution to ensure the mouse cursor alignment ($A_{mouse}$) remains 1:1.

Setup & File Navigation

1. Windows Path: Press Win + R, type %LOCALAPPDATA%\Introversion\Prison Architect\, and hit Enter.
2. Mac Path: ~/Library/Application Support/Prison Architect/
3. The Target: Open preferences.txt with Notepad++ or TextEdit.
4. Pro Tip: If you cannot find the file, launch the game once and click “Open Save Folder” from the main menu; then go up one directory level.

Optimized “High-DPI” Configuration Block

ScreenW              1920
ScreenH              1080
ScreenWindowed       true
ScreenMultiSampled   true
UiScale              1.000000

Configuration Breakdown & Technical Purpose

Parameter	Recommended Value	Technical Purpose
UiScale	1.000000	The Master Fix. Resets the UI to standard 100% scaling.
ScreenW / H	0	Setting both to 0 forces the game to use your native desktop resolution.
ScreenWindowed	true	Prevents “Resolution Mismatch” crashes during the first boot.
ScreenMultiSampled	true	Enables FSAA to smooth out the scaled UI icons.

HowTo: Engineering the UI Clarity Pipeline

Follow these GameEngineer.net technical steps to resolve scaling artifacts in the 2026 build:

1. The “1.0” Reset: The most common cause of a “Broken UI” is an accidental keypress. In the preferences.txt, search for UiScale. If the value is something like 0.5000 or 2.0000, your UI will be unusable. Change it to 1.000000 to restore the baseline.
2. Hotkeys vs. Config: You can live-adjust the scale using the + and - keys (near the Backspace key, not the Numpad). However, if your keyboard layout makes the + key unreachable (requiring Shift), the game often fails to register the input. The .txt edit is the only “Hard Fix.”
3. High-DPI Mouse Alignment: If your icons look right but you have to click next to a button to activate it, your Windows Scaling is interfering. Right-click Prison Architect.exe > Properties > Compatibility > Change high DPI settings > Check Override high DPI scaling behavior and set it to Application.
4. 4K/Ultra-Wide Tuning: For 4K monitors, a UiScale of 1.0 is usually too small. We recommend experimenting in increments of 0.2. Try 1.200000 or 1.400000 for 27-inch 4K displays to maintain the optimal balance between information density and readability ($D_{info}$).
5. The “Clean Slate” Method: If your file is corrupted and the game won’t start, simply delete preferences.txt. The engine will generate a fresh one with default 1080p settings on the next launch.

Technical Explanation: UI Scaling and Coordinate Mapping

Prison Architect uses a Coordinate Mapping System where the UI layer is drawn on top of the simulation layer.

$$Mouse_{input} = \frac{Cursor\_Pos}{Scale_{win} \times Scale_{ui}}$$

When you change the UiScale, you are changing the multiplier for the hitboxes of every button in the game. If this value becomes desynced from your ScreenW/H, the “hitbox” of a button might be at $(500, 500)$ while the visual icon is drawn at $(400, 400)$. Resetting the UiScale to 1.0 in your preferences.txt forces these two coordinate systems to re-align perfectly.