Call of Duty 2 – Client & Server Side Files Explained
In Call of Duty 2 modding, understanding which files belong on the client (players), the server, or both is essential.
Mods are packaged in .iwd files (renamed ZIP archives). Files that must be on both sides must be identical (byte-for-byte match).
Any difference causes “iwd/sum name mismatch” or purity errors when sv_pure 1 is enabled.
Key Rule: Any file listed as Both must be exactly the same on the server and all connecting clients. Even a single byte difference will prevent players from joining.
File Types Overview
| File Type / Folder | Extension | Primary Side | Description |
|---|---|---|---|
| Images | .iwi | Client | Textures, skins, HUD icons, and menu graphics. |
| Sounds | .wav, .mp3 | Client | Actual audio data for weapons, voice lines, and ambient sounds. |
| Models | .xmodel | Client | 3D meshes for players, weapons, and map objects. |
| Animations | .xanim | Client | Movement and animation data for models and weapons. |
| Effects | .efx | Client | Particle effects for smoke, fire, explosions, etc. |
| Sound Aliases | .csv | Both | Links sound names used in scripts to actual audio files (soundaliases folder). |
| Scripts | .gsc, .csc | Server (.gsc) Client (.csc) |
.gsc = server-side game logic and rules. .csc = client-side scripts (visual effects, UI, etc.). |
| Weapon Stats | (no extension) | Both | Damage, recoil, clip size, etc. Located in weapons/mp/. |
| Menus | .menu | Client | In-game UI layout and menu design. |
| Materials | (no extension) | Client | Shader instructions (how textures reflect light, scroll, etc.). |
| String Tables | .csv | Both | Text used for rankings, weapon names, UI labels, etc. |
Important Caveats & Best Practices
- Both-side files must match exactly — Sound aliases, weapon stats, and string tables are the most common causes of mismatch errors.
- .gsc vs .csc — .gsc files run on the server (game logic). .csc files are client-side only and are used for visual/effects scripting.
- Pure server logic can stay outside of .iwd files in the
mods/yourmod/folder on the server — these files are never sent to clients.
Using “svr” in IWD Filenames (Server-Side Only)
To keep client download sizes small and avoid sending unnecessary files, place server-only content in IWD files prefixed with svr.
Example: svr_mymod_logic.iwd
Benefit: Clients will not download IWDs that begin with svr. This is perfect for pure server scripts, configs, or internal data.
Recommended approach:
- Client-visible assets (images, sounds, models, menus, etc.) → normal IWDs (often prefixed with
z_to override stock files). - Server-only files →
svr_*.iwdor leave them extracted directly in the mod folder on the server. - Always test with
sv_pure 1to catch any mismatches early.
This method keeps your mod fast to download for players while giving you full control on the server side.
CoD2 Modding Guide • Client vs Server Files • Verified April 2026
