How to edit the Main, login screen and client resolution

The client is the first thing every player sees and interacts with. Customizing it — even just changing the login screen image — signals that your server is its own unique experience, not just a generic MU installation.

What the Main.exe controls

WHAT'S INSIDE MAIN.EXE:

SERVER CONNECTION INFORMATION:
→ The IP address or hostname of your ConnectServer
→ The port the client connects to (e.g., 44405)
→ Some distributions use external config files for this — others hardcode it in the binary

INTERFACE TEXTS:
→ Window title bar text ("MU Online" can be changed to your server name)
→ Button labels ("Connect", "Create Account", "Exit")
→ Version string displayed in the client (e.g., "Season 6 Ep. 3")

CLIENT BEHAVIOR:
→ Protocol version used for server communication
→ Whether the client uses encryption for specific packet types
→ Some visual behavior settings

WHAT'S IN SEPARATE FILES (NOT in Main.exe):
→ Login background image — in the Data/ or BMP/ folder
→ In-game texts (item names, monster names) — in text/language files
→ Configuration (resolution, graphics options) — in .cfg or .ini files
→ Sounds and music — in Sound/ and Music/ folders

Method 1: Changing IP via config file (easy)

CHECK FOR A CONFIG FILE FIRST — IT'S MUCH EASIER:

Look in your client folder for:
→ IP.txt, server.ini, Connect.ini, ServerList.txt, serverinfo.txt, or similar
→ These files contain the ConnectServer address in plain text

COMMON CONTENT FORMATS:

Format A (single line):
127.0.0.1

Format B (with port):
127.0.0.1 44405

Format C (INI style):
[ConnectServer]
IP = 127.0.0.1
Port = 44405

EDITING:
1. Open the file in Notepad or Notepad++
2. Replace the existing IP with your server's IP or hostname
3. Save the file in the SAME format (don't change the structure)
4. Test by opening the client — it should connect to your server

IF THE CLIENT READS THIS FILE:
→ You can distribute the config file separately (or patch it via launcher)
→ Changing the server IP is as simple as updating one text file
→ Players never need to re-download the entire client for an IP change

Method 2: Hex-editing Main.exe (hardcoded IP)

HEX EDITING — FOR HARDCODED IPs IN THE BINARY:

TOOLS NEEDED:
→ HxD (free hex editor) — download from mh-nexus.de

STEP 1 — WORK ON A COPY:
→ Copy Main.exe to Main_BACKUP.exe before touching anything
→ Open HxD → File → Open → select the COPY of Main.exe

STEP 2 — FIND THE CURRENT IP:
→ Edit → Find → find: (set search type to "Text string")
→ Search for the current IP (e.g., "127.0.0.1" or the IP the client was pointing to)
→ Or: search for a common default IP like "game1.webzen.com"
→ HxD highlights the bytes containing the IP string

STEP 3 — EDIT THE IP:
→ Click on the first character of the IP in the right panel (the text/ASCII view)
→ Type your new IP directly
→ CRITICAL: the new IP must be exactly the same length or shorter
  → "45.67.89.100" (14 chars) replacing "127.0.0.1" (9 chars) won't fit
  → Solution: pad shorter IPs with spaces or null bytes (0x00) AFTER the IP
  → Example: "45.67.89.10" = 11 chars, original "127.0.0.1" = 9 chars
    → Use a shorter IP or change the client's IP reference location

STEP 4 — HANDLE LENGTH DIFFERENCES:
→ If your IP is SHORTER: fill remaining bytes with 0x00 (null bytes in hex view)
→ If your IP is LONGER: this is more complex — the binary structure may not allow it
  → Solutions: use a shorter hostname, or find a config-file based method

STEP 5 — SAVE AND TEST:
→ File → Save (saves the modified copy)
→ Open the game using this modified copy
→ If it connects to your server: success
→ If the game crashes: the edit was wrong — use the backup and try again

Changing the login screen image

CUSTOMIZING THE LOGIN/SELECT BACKGROUND:

FIND THE ORIGINAL IMAGE:
→ Browse the client folder for subfolders: Data/, BMP/, Texture/, Image/
→ Look for image files with names like:
  → select.jpg, back.jpg, login.bmp, character.jpg, charselect.jpg
→ Right-click → Properties → Details to see the exact dimensions

CREATE YOUR CUSTOM IMAGE:
→ Use your original image as the size reference
→ Tools: Photoshop, GIMP (free), or Canva
→ Design your server's logo, character art, or themed background
→ Export in the SAME format as the original (same .jpg or .bmp extension)
→ Name the file EXACTLY the same as the original (case-sensitive on some systems)
→ Save at EXACTLY the same dimensions (resize if needed)

REPLACE THE ORIGINAL:
1. Rename the original to back_ORIGINAL.jpg (keep as backup)
2. Place your new image with the original's exact name in the same folder
3. Open the client → the new image should appear on the login/select screen

COMMON REASONS THE IMAGE DOESN'T APPEAR:
→ File name is wrong (even capitalization: Select.jpg vs select.jpg matters)
→ Image format mismatch (client expects BMP but you saved as JPG)
→ Wrong dimensions (image is distorted or not loading)
→ Image too large (some clients have a size limit — keep under 2 MB)

Editing WTF and text files

CUSTOMIZING IN-GAME TEXTS:

WHAT TEXT FILES CONTAIN:
→ Item names and descriptions
→ Monster names
→ Skill and spell names
→ System messages ("You've been disconnected from the server")
→ Event messages

FINDING THE FILES:
→ Look in: Lang/, Language/, or the main client folder
→ Common file names: ItemList.txt, MonsterList.txt, SpellList.txt
→ Some seasons use binary formats (.dat) — these require specialized tools

EDITING SAFELY:
→ Use Notepad++ (not plain Notepad) — it shows character encoding
→ Before editing: check the file encoding (Encoding menu in Notepad++)
  → Usually Windows-1252 or UTF-8
→ Edit ONLY the text content, NOT the structure (don't add or remove tab characters)
→ Save in the SAME encoding as the original

ADDING YOUR SERVER NAME:
→ Find references to "MU Online" or "WEBZEN" in the text files
→ Replace with your server's name
→ The window title usually comes from the Main.exe binary or a resource file

Fixing broken accent characters

FIX FOR ACCENTED CHARACTERS (á, é, ñ, ç, ü, etc.):

SYMPTOMS:
→ Characters that should have accents show as "?" or "□" or random symbols
→ Affects: item names, chat text, NPC messages

CAUSE:
→ The client's internal encoding doesn't match your Windows locale setting

FIX 1 — SYSTEM LOCALE (try this first):
1. Control Panel → Region → Administrative tab
2. "Language for non-Unicode programs" → Change system locale
3. Select: Spanish (Spain), Spanish (Mexico), or Portuguese (Brazil)
4. Click OK → restart Windows
5. Open the client → accents should now display correctly

FIX 2 — FONT FILES:
→ The client uses its own custom font files (usually in a Fonts/ folder or embedded)
→ If the font doesn't include accented characters: they can't display
→ Community distributions for LATAM often have pre-patched font files
→ Look in your distribution's forum for "font fix" or "accent fix" patches

FIX 3 — TEXT FILE ENCODING:
→ If you edited text files and introduced the encoding mismatch:
  → In Notepad++: open the file → Encoding → Convert to ANSI (Windows-1252)
  → Save → the accents should work again

Resolution and widescreen

SETTING THE CLIENT RESOLUTION:

DEFAULT MU S6 RESOLUTIONS:
→ 800x600, 1024x768, 1280x960, 1280x1024 (4:3 aspect ratios)
→ Some distributions add 1920x1080 via widescreen patches

CHANGING RESOLUTION:
→ Look for Setup.exe in the client folder → runs a configuration dialog
→ Or look for Main.ini or resolution.cfg with a "Width" and "Height" setting
→ Change values to your monitor's resolution

WINDOWED MODE:
→ Many clients support: right-click Main.exe → Properties → Shortcut → Target
→ Add: -window or -windowed at the end of the path
→ Example: "C:\MuServer\Main.exe" -window

FOR WIDESCREEN MONITORS (16:9):
→ The original client renders in 4:3 — on a 16:9 monitor it appears stretched or with black bars
→ Recommended: tell your GPU to "maintain aspect ratio" (forces black bars — no stretching)
  → NVIDIA Control Panel → Display → Adjust desktop size → Aspect ratio
  → AMD Radeon Settings → Display → GPU Scaling → Maintain aspect ratio
→ Community widescreen patches: search your distribution's forum for "widescreen patch"

Pair this with the client installer tutorial (for packaging the edited client into a professional installer), the launcher tutorial (for distributing updates to the client files without full reinstalls), and the common server errors tutorial (for fixing client crashes that happen after incorrectly edited Main files).

Frequently asked questions