Pure Mode is a server configuration feature in FiveM that validates client game files against a predefined list, preventing players from joining with modified files that could provide unfair advantages or destabilize gameplay.

Technical Implementation

Pure Mode operates through the sv_pureLevel server convar:

# In server.cfg
sv_pureLevel 0  # Disabled (default)
sv_pureLevel 1  # Light Mode - Allows some visual/audio mods
sv_pureLevel 2  # Harsh Mode - Blocks all client modifications

Mode Differences

Level 0 (Disabled)

• No file validation performed
• All client modifications allowed

Level 1 (Light)

• Permits: .ytd texture files, .ydd/.ydr model variations, audio modifications
• Blocks: .ysc scripts, .asi injectors, modified executables

Level 2 (Harsh)

• Blocks all file modifications except those explicitly whitelisted by FiveM
• Includes graphical enhancement mods and custom radio stations

Client Connection Process

1. Player attempts connection with modified files
2. Server performs file hash validation
3. If mismatches detected: “Files have been modified” error appears
4. Player must restart FiveM to load vanilla files

Limitations and Considerations

Not a Complete Anti-Cheat Solution

• Only validates files loaded at startup
• Cannot detect memory modifications or external cheats
• Should be combined with dedicated anti-cheat resources

Performance Impact

• Initial connection may take 2-5 seconds longer for validation
• No runtime performance impact after connection

False Positives

• Some legitimate accessibility mods (colorblind filters, UI scaling) may be blocked
• Server owners cannot whitelist specific modifications

Recommended Implementation

For competitive servers:

sv_pureLevel 2
# Combine with anti-cheat resource
ensure your-anticheat-resource

For roleplay/casual servers:

sv_pureLevel 1
# Allow visual customization while blocking exploits

Summary: Pure Mode provides baseline file integrity verification for FiveM servers but requires supplementary anti-cheat measures for comprehensive protection against cheating.