Modding guidelines

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If you just want to play see mod list.

Creating mod

To make your own mod you need to create subdirectory in /Mods/ with name that will be used as identifier for your mod.

Main mod is file called mod.json and should be placed into main folder of your mod, e.g. Mods/myMod/mod.json

All content of your mod should go into Content directory, e.g. Mods/myMod/Content/. In future it will be possible to replace this directory with single .zip archive.

Example of how directory structure of your mod may look like:

                    data/    - unorganized files, mostly bitmap images (.bmp, .png, .pcx)
                    config/  - json configuration files
                    maps/    - h3m maps added or modified by mod
                    music/   - music files. Mp3 is fully supported, ogg may be added if needed
                    sounds/  - sound files, in wav format.
                    sprites/ - animation, image sets (H3 .def files or VCMI .json files)
                    video/   - video files, .bik or .smk

Updating mod to next version of VCMI

See Modding changelog

Creating mod file

All VCMI configuration files use JSON format so you may want to familiarize yourself with it first.

Mod.json is main file in your mod and must be present in any mod. This file contains basic description of your mod, dependencies or conflicting mods (if present), list of new content and so on.

Minimalistic version of this file:

    "name" : "My test mod",
    "description" : "My test mod that add a lot of useless stuff into the game"

See Mod file Format for its full description.

Overriding graphical files from Heroes III

Any graphical replacer mods fall under this category. In VCMI directory <mod name>/Content acts as mod-specific game root directory. So for example file <mod name>/Content/Data/AISHIELD.PNG will replace file with same name from H3Bitmap.lod game archive.

Any other files can be replaced in exactly same way.

Note that replacing files from archives requires placing them into specific location:

H3Bitmap.lod -> Data
H3Sprite.lod -> Sprites
Heroes3.snd  -> Sounds
Video.vid    -> Video

This includes archives added by expansions (e.g. H3ab_bmp.lod uses same rules as H3Bitmap.lod)

Replacing .def animation files

Heroes III uses custom format for storing animation: def files. These files are used to store all in-game animations as well as for some GUI elements like buttons and for icon sets.

These files can be replaced by another def file but in some cases original format can't be used. This includes but not limited to:

  • Replacing one (or several) icons in set
  • Replacing animation with fully-colored 32-bit images

In VCMI these animation files can also be replaced by json description of their content. See Animation Format for full description of this format.

Example: replacing single icon

	// List of replaced images
	"images" : 
	[	  // Index of replaced frame
		{ "frame" : 0, "file" : "HPS000KN.bmp"} 
		               //name of file that will be used as replacement

"High resolution main menu" mod can be used as example of file replacer mod.

Packaging mod into archive

For distribution it is recommended to package mod into .zip archives. To create .zip archive you need to have file archiver like 7zip

File structure of packaged mod should look like this

<modname>.zip/   <- Zip archive with high compression ratio
  modname/       <- Archive contains main mod directory 
    mod.json     <- main mod file <- Uncompressed archive with all mod data
       ...       <- Identical to Content directory

You can create such structure using following instructions:

  • Go to Mods/<modname>/Content directory
  • Select all files in this directory and create archive with following parameters:
    • Archive name:
    • Format: ZIP
    • Compression level: None/Store only
  • Move created archive into Mods/<modname> directory and remove no longer needed Content directory.
  • Go to Mods/ directory
  • Create archive from your mod with following parameters:
    • Archive name: <modname>.zip
    • Format: ZIP
    • Compression level: Maximum

Resulting archive is recommended form for distributing mods for VCMI

Releasing mods

Right now there are 3 ways to bring your mod to players:

  • Manual download
  • VCMI Repository
  • Private repository

Manual download

You can upload mod into some online file hosting and add link with description of your mod into mod list.

Note: Avoid using services that require registration or remove files after certain period of time (examples are Wikisend and 4shared). Instead you may use any of the services listed below:

VCMI Repository

Another option is to add mod into VCMI repository. This will allow players to install mods directly from VCMI Launcher without visiting any 3rd-party sites.

Check for more details in Mods repository.

Private repository

It it also possible to create your own repository. To do this you need to own your own server capable of file hosting or use file service that provide direct download links (e.g. Dropbox with enabled public directory).

Providing own repository allows you to deliver any new mods or updates almost instantly and on the same level of integration with VCMI as mods from VCMI repository.

To create empty repository you need to:

  • Create directory that will contain repository
  • Create file named "repository.json" in it

To add mods into such repository you need to:

  • Copy packaged archive <modname>.zip into repository directory
  • Copy mod information from mod.json into repository.json
  • Add two extra fields about this mod into repository.json:
    • "download" - public link that can be used to download the mod, including http:// prefix
    • "size" - size of mod, in kilobytes. VCMI will use this number to inform player on size of the mod.

Example on how mod entry should look in repository.json

  "exampleMod" // ID of the mod, lowercase version of mod directory name
    "name" : "My test mod",
    "description" : "My test mod that add a lot of useless stuff into the game",
    "author" : "Anonymous",
    "contact" : "",
    "modType" : "Graphical",
    "depends" :

    "download" : "",
    "size" : 1234 //size, in kilobytes

    //Note that entries that refer to files, e.g. "heroes". "creatures", "artifacts" and such
    //are not necessary in repository.json and therefore can be removed

When repository is ready you can share public link to repository.json with players. New repositories can added to vcmi launcher from settings tab.

Dropbox: enabling public directory

New accounts create on Dropbox no longer have Public directory enabled by default. You can enable it using this link

This will give you directory named "Public" as well as option "get public link" for all files inside this directory.

Modding related articles

Main articles
Modding changelog Modding guidelines Mod Handler

Mod file Format
Town Format Creature Format Hero Classes Format
Artifact Format Animation Format Hero Format
Bonus Format Object Format Spell Format

Work-in-progress formats
Building bonuses Map format
Bonus Type Format Random map template

Outdated pages
Mod system proposal