Couple of things to note before downloading this extension:

- Vortex does NOT save/store your Steam credentials and will not do so in the future, as per guidelines in Steam's T&S.
- Vortex 1.5.x and higher is required.
- Running the file verification process will cause Vortex to run a purge operation, this is done to restore any replacement files and avoid breaking your mods.
- DO NOT install or deploy mods while the file verification process is running as it will most probably end (very) badly.
- Closing Vortex during the file verification process will leave your game in an unknown state. You will have to run it again on startup to ensure the game files are not corrupted.
- Please report any issues you experience with this extension in the bugs tab on this page.

How to use:

Steam Workshop Page:
A new page has been added to allow users to browse Steam Workshop mods - you will need a Steam Web API key; the extension will inform you where and how to generate one.

The UI is currently fugly - I'm not a front-end developer - will do my best to improve it in the future.

Depending on the game, some mods might generate installation errors as the game extensions themselves are not prepared to deal with Steam Workshop mods. I can currently only confirm it's working as expected with Rimworld and Kenshi. Let me know in the posts area if you've tested any other games (which are bundled with Vortex) and I'll fix the game extensions.

Finally - if anyone knows how to query mod metadata by published file id through the Steam API, please get in touch with me so I can add an API based dependency resolution.

File Verification:
As a Vortex user - a new button has been added to the toolbar on the mods page, "Verify Files" with the Steam icon. Simply click on it to purge your mods and start the Steam Authentication process - the file verification process will kick off if valid credentials are provided; if any damaged/tampered files are detected, Vortex will allow you to choose which files you wish to restore to their original state.

Why would I use this extension instead of Steam's own file verification system you ask?
- Vortex will allow you to select which files to restore
- Game extensions can make use of this extension's API to automatically detect file corruption and restore the files for you.

As an extension developer - API functionality has been added to allow game extensions to start the Steam game file verification processcontext.api.ext.steamkitVerifyFileIntegrity(parameters: ISteamKitParameters, gameId: string);

export interface ISteamKitParameters {
  Username?: string;
  Password?: string;
  // Not used, probably never will be.
  RememberPassword?: boolean;
  ManifestOnly?: boolean;
  CellId?: number;

  // Files need to be separated by /r or /n
  FileList?: string;

  // Discovery path
  InstallDirectory?: string;
  VerifyAll?: boolean;
  MaxServers?: number;
  MaxDownloads?: number;
  LoginId?: number;

  // Steam app id
  AppId?: number;

  PubFile?: string;
  UgcId?: string;
  Branch?: string;
  BetaBranchPassword?: string;
  DepotIdList?: number[];
  ManifestIdList?: number[];
}

At a minimum you will need to provide the Steam `AppId` and game `InstallDirectory` (discovery path)

An extensive developer's guide will be provided with examples soon-ish.

How it works:

This extension will read your Steam game manifests to ascertain which Steam depots your Steam accounts have access to, including any DLC, to generate a file hash list - it will then query the Steam API to ensure that the hashes it generated match the hashes of the original files; if any mismatches are found, Vortex will inform you of this and allow you to download and restore the original files.

Future plans:

- Steam mods browser/downloader
- Improved API functionality for extension developers

This extension uses SteamKit2 and DepotDownloader to communicate with Steam's API service.