Pure Mode in FiveM: Server-Side File Integrity Enforcement

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

Player attempts connection with modified files
Server performs file hash validation
If mismatches detected: “Files have been modified” error appears
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.