Addoninfo.txt

The plain-text file addoninfo.txt contains the KeyValues 1 structure AddonInfo specifying an addon’s metadata: its author, content flags, description, title, and version. This file and its functionality were introduced with the Left 4 Dead engine branch.

Both the Source Engine and the deprecated external application addoninstaller.exe will parse this file, though with significant differences. Source will parse this file from all addons listed in addonlist.txt when loading search paths from gameinfo.txt at startup and with subsequent calls to ConCommand update_addon_paths. Source will retrieve metadata for all Steam Workshop addons from the Steam Workshop, overriding content in addoninfo.txt. addoninstaller.exe only parses addoninfo.txt when staging addons during user-initialized installation.

Specification

In the following specification, these terms will have the following meanings:

• shall indicates a mandatory requirement; and
• should indicates a recommendation.

The Source Engine will expect a specific KeyValues 1 structure in addoninfo.txt, specified below:

• You shall save addoninfo.txt with an UTF-8-compatible encoding.
• You shall have at least one KeyValues block.
• You should define the name of the first KeyValues block as AddonInfo.
• You should populate the first KeyValues block with at least one key-value entry from table “Valid AddonInfo Keys”:

• You should provide a title, author, and version.
• You should provide at least one content tag.

Valid AddonInfo Keys

Key	Type	Length	Default Value	Description
addontitle	wchar_t	127	L4D360UI_Addon_None_Specified	The addon’s title.
addonauthor	wchar_t	119	L4D360UI_Addon_None_Specified	The addon’s author.
addonDescription	wchar_t	1023	L4D360UI_Addon_None_Specified	The addon’s description. Left 4 Dead 2 will truncate those of Steam Workshop addons to 499 characters [citation needed ].
addonversion	wchar_t float (addoninstaller.exe)	31	0.0 1.0 (addoninstaller.exe)	The addon’s version. Conventionally a decimal number in the format major.minor, but you may write any string.
addonContent_Campaign	int	N/A	0	If the addon contains custom campaigns. If the value is 0, then the addon does not contain the specified content; otherwise, the addon contains the specified content.
addonContent_Map	int	N/A	0	If the addon contains custom campaigns or custom maps.
addonContent_Skin	int	N/A	0	If the addon contains custom skins.
addonContent_weapon	int	N/A	0	If the addon contains custom weapon skins.
addonContent_BossInfected	int	N/A	0	If the addon contains custom boss infected skins.
addonContent_CommonInfected	int	N/A	0	If the addon contains custom common infected skins.
addonContent_Survivor	int	N/A	0	If the addon contains custom survivor skins.
addonContent_Sound	int	N/A	0	If the addon contains custom sounds.
addonContent_Music	int	N/A	0	If the addon contains custom music.
addonContent_Script	int	N/A	0	If the addon contains custom scripts.
addonContent_prop	int	N/A	0	If the addon contains custom props.

Non-existent or deprecated keys

Avoid writing these keys. All games ignore these keys. Valve provided these keys in the respective addoninfo.txt copies packaged with the example campaigns “DEADLINE” and “DEADLINE 2”.

Key	Description
addonSteamAppID	The AppID of the addon’s target game. Only addoninstaller.exe uses this.
addonTagline	The addon’s subtitle or tagline. May have had a similar purpose to key poster/posterTagline in mission files.
addonAuthorSteamID	The addon author’s SteamID. Supposedly used to construct a URL to the author’s Steam profile page.
addonSteamGroupName	The addon’s Steam group. Supposedly used to construct a URL to the addon’s Steam group page.
addonURL0	The addon’s homepage. May have had a similar purpose to key Website in mission files.
addonContent_Survival addonContent_Versus addonContent_Scavenge	If the addon provides custom campaigns supporting the Survival, Versus, or Scavenge game modes. This functionality is provided by mission files.
addonContent_Prefab	If the addon provides custom Hammer prefabs.
addonContent_Spray	If the addon provides custom logos.
addonContent_BackgroundMovie	If the addon provides custom background movies.
Content_Weapon	If the addon provides custom weapons (e.g., “…a new weapon, i.e. guns, explosives, booby traps, hot tar, etc.”).
Content_WeaponModel	If the addon provides custom weapon model.
addonDescription_locale	The addon’s description localized for locale locale, where locale is an ISO 639-1 code in ALL CAPS.

Content tag handling

An addon’s AddonInfo content keys provide an abstraction over Source’s implementation-specific content tags. Source will convert all keys into an internal representation (typically, a bitfield). A content key may correspond to its internal tag; some keys provide redundant meaning useful only to authors and distributors. Source will use these content tags to describe and filter addons in the CBaseModFrame Addons.

Bug:A prop’s collision mesh throughout the current session will be decided by whichever addon or pack-file loads first.

The game will always load the effective first collision mesh until the current session ends.

This was tested on the propane tank model.

Todo: Move this to an appropriate page

  [todo tested in ?]

In Left 4 Dead and Alien Swarm

Left 4 Dead maintains a one-to-one correspondance between content keys and content tags. The handler closely resembles that found in the Alien Swarm SDK.

Source will generate the content label by concatenating the VGUI localization strings corresponding to the given content tag followed into an array of 60 wide characters. The right-most comma will always be replaced with a NULL terminator. The effective length of the label is 59 characters since the last character will always be a NULL terminator.

In Left 4 Dead 2

Left 4 Dead 2 stores the content keys for each addon as an int16_t representing the following bitfield (assume little-endian):

Left 4 Dead 2 content tag bitfield

Bit	15	14	13	12	11	10	9	8	7	6	5	4	3	2	1	0
Tag	N/A	N/A	N/A	N/A	CONTENT_ITEM	CONTENT_UI	CONTENT_SCRIPT	CONTENT_SOUND	CONTENT_SURVIVOR	CONTENT_INFECTED	CONTENT_MUTATION	CONTENT_WEAPON	CONTENT_SKIN	CONTENT_MISCELLANEOUS	CONTENT_CAMPAIGN	CONTENT_RESERVED
Key	N/A	N/A	N/A	N/A	addonContent_prop	N/A	addonContent_Script	addonContent_Sound addonContent_Music	addonContent_Survivor	addonContent_BossInfected addonContent_CommonInfected	N/A	addonContent_Weapon	addonContent_Skin	N/A	addonContent_Campaign addonContent_Map	N/A

The content tags CONTENT_MISCELLANEOUS, CONTENT_MUTATION, and CONTENT_UI can be set only through the Steam Workshop.

Source will generate the content label by concatenating the VGUI localization strings corresponding to the given content tag followed into an array of 60 wide characters. The right-most comma will always be replaced with a NULL terminator. The effective length of the label is 59 characters since the last character will always be a NULL terminator.

Examples

The following are samples—both modern and historic—of addoninfo.txt. Avoid using the “DEADLINE” or “DEADLINE 2” samples as templates: you will be shipping redundant keys.

Minimal compliant AddonInfo

AddonInfo {
	addontitle			"こんにちは、世界！"	// Title is interpreted as a UTF8 string;
												// prefer codepoints in the Basic
												// Multilingual Plane.
	addonauthor			ValveDeveloperWiki
	addonversion		something				// This can be anything and not just a float
	addonDescription	"This is a sample.

Note that the KeyValues parser will, in a quoted string, a) parse all
whitespace literally and b) // ignore all C-style comments. You could
probably use this to validate a KeyValues parser too.
"
	addonContent_Campaign	1
	addonContent_Survivor	-1
	addonContent_Sound		3.14159265
}

“DEADLINE”

Download Valve’s “DEADLINE” campaign from here. The following snippet matches the original exactly as of April 30, 2023.

// The addoninfo.txt file is a metadata file that is required by all Left 4 Dead Add-ons. 


"AddonInfo"
{
        addontitle		"Dead Line"                                     // Add-on title that shows up in Add-ons list. ~20 chars max
        addonversion	        1.3                                             // Add-on version.
        addontagline		"Catch the last subway... out of hell."	        // Add-on tagline or wrap-up- a short description. ~100 chars max
	addonauthor 		"Valve"                                         // Name/alias of the author
	addonauthorSteamID 	"http://steamcommunity.com/groups/Valve"        // Steam Profile URL of author or group

	addonContent_Campaign		1 	                                //This addon provides muliple connected maps with a finale

	addonURL0 "http://media.steampowered.com/apps/513/deadline.html"	//An html home page for the add-on that includes a download link.

	// short description that appears in the Add-on list screen...
	addonDescription "Survivors must escape on a subway train in this short tutorial example campaign. Get source files and tools for creating your own campaigns by downloading the Left 4 Dead Authoring tools SDK, which is available under the 'Tools' tab in Steam."
	
	// Authors can add localized descriptions here. (Not yet supported)
	addonDescription_FR "Les survivants doivent s'échapper en métro dans cette carte du tutoriel. Obtenez les fichiers et les outils pour créer vos propres cartes en chargeant les outils de création SDK Left 4 Dead qui sont disponibles sous l'onglet "Outils" sur Steam."	

}

“DEADLINE 2”

Download Valve’s “DEADLINE 2” campaign from here. The following snippet matches the original exactly as of April 30, 2023.

// The addoninfo.txt file is a metadata file that is required by all Source Engine Add-ons.

"AddonInfo"
{
     addonSteamAppID         550                                                     // 500 is the app ID for Left 4 Dead, 550 for Left 4 Dead 2
     addontitle              "Dead Line 2"                                           // Add-on title that shows up in Add-ons list. ~20 chars max
     addonversion	     1.0                                                     // Add-on version.
     addontagline            "Catch the last subway... out of hell... Again!"	     // Add-on tagline or wrap-up- a short description. ~100 chars max
     addonauthor             "Valve"                                                 // Name/alias of the author
     addonSteamGroupName     "deadline2add-on"                                       // (Optional) Steam group related to the add-on. We use this to construct a URL to the group page.
     addonauthorSteamID      "YasserMalaika"                                         // (Optional) Steam ID of author. We use this to construct a URL to the author's page.
     addonContent_Campaign   1 	                                                     //This addon provides muliple connected maps with a finale
     addonURL0               "http://media.steampowered.com/apps/513/deadline2.html" //An html home page for the add-on that includes a download link.

     // short description that appears in the Add-on list screen...
     addonDescription        "Survivors must escape on a subway train in this short tutorial example campaign. Get source files and tools for creating your own campaigns by downloading the Left 4 Dead 2 Authoring tools SDK, which is available under the 'Tools' tab in Steam."

     // Authors can add localized descriptions here. (Not yet supported)
     addonDescription_FR     "Les survivants doivent s'échapper en métro dans cette carte du tutoriel. Obtenez les fichiers et les outils pour créer vos propres cartes en chargeant les outils de création SDK Left 4 Dead 2 qui sont disponibles sous l'onglet "Outils" sur Steam."	
 
}

See also

• L4D Campaign Add-on Tutorial
• L4D 2 Campaign Add-on Tutorial
• Deadline Mission File