This page is just a reference of all the known Steam APIs, I do not know how they work. Please do not email me with questions.
UNDOCUMENTEDCanSubscribe

Check if the user can subscribe to the published file

https://api.steampowered.com/IPublishedFileService/CanSubscribe/v1/
NameValueTypeRequiredDescription
click to setstring Yes Access key
uint64 No

Deletes a published file.

https://partner.steam-api.com/IPublishedFileService/Delete/v1/
NameValueTypeRequiredDescription
click to setstring Yes Access key
uint64 Yes Published file id of the file we'd like to delete.
uint32 Yes

Retrieves information about a set of published files.

https://api.steampowered.com/IPublishedFileService/GetDetails/v1/
NameValueTypeRequiredDescription
click to setstring Yes Access key
uint64[] Yes Set of published file Ids to retrieve details for.
bool Yes If true, return tag information in the returned details.
bool Yes If true, return preview information in the returned details.
bool Yes If true, return children in the returned details.
bool Yes If true, return key value tags in the returned details.
bool Yes If true, return vote data in the returned details.
bool Yes If true, return a short description instead of the full description.
bool Yes If true, return pricing data, if applicable.
bool Yes If true, populate the metadata field.
ELanguage NoSpecifies the localized text to return. Defaults to English.
uint32 Yes Return playtime stats for the specified number of days before today.
uint32 Yes
bool Yes Strips BBCode from descriptions.
EPublishedFileRevision NoReturn the data for the specified revision.
bool NoIf true, then reactions to items will be returned.
bool Yes Admin tool is doing a query, return hidden items

Get sub section data (for table of contents, a specific section, or all)

https://api.steampowered.com/IPublishedFileService/GetSubSectionData/v1/
NameValueTypeRequiredDescription
click to setstring Yes Access key
uint64 Yes
bool Yes
uint64 Yes
{enum} NoReturn the data for the specified revision.

Retrieves a count of files published by a user. Uses the same messages as GetUserFiles but totalonly must be true.

https://api.steampowered.com/IPublishedFileService/GetUserFileCount/v1/
NameValueTypeRequiredDescription
click to setstring Yes Access key
uint64 Yes Steam ID of the user whose files are being requested.
uint32 Yes App Id of the app that the files were published to.
uint32 NoShortcut Id to retrieve published files from.
uint32 NoStarting page for results.
uint32 NoThe number of results, per page to return.
string NoType of files to be returned.
string NoSorting method to use on returned values.
uint32 NoFilter by privacy settings.
string NoTags that must be present on a published file to satisfy the query.
string NoTags that must NOT be present on a published file to satisfy the query.
{message} Yes Required key-value tags to match on.
uint32 NoFile type to match files to.
uint32 Yes App Id of the app that published the files, only matched if specified.
string Yes Match this cloud filename if specified.
uint32 NoAllow stale data to be returned for the specified number of seconds.
int32 NoSpecifies the localized text to return. Defaults to English.
{message} NoAt least one of the tags must be present on a published file to satisfy the query.
{enum} NoFilter out items that have these content descriptors.
bool Yes Admin tool is doing a query, return hidden items
bool NoIf true, only return the total number of files that satisfy this query.
bool NoIf true, only return the published file ids of files that satisfy this query.
bool NoReturn vote data
bool Yes Return tags in the file details
bool NoReturn key-value tags in the file details
bool Yes Return preview image and video details in the file details
bool Yes Return child item ids in the file details
bool NoPopulate the short_description field instead of file_description
bool Yes Return pricing information, if applicable
bool NoPopulate the metadata field
uint32 Yes Return playtime stats for the specified number of days before today.
bool Yes Strips BBCode from descriptions.
bool NoIf true, then reactions to items will be returned.
uint32 Yes Backwards compatible for the client.
{enum} NoReturn the data for the specified revision.
bool Yes Return list of apps the items belong to

Retrieves files published by a user.

https://api.steampowered.com/IPublishedFileService/GetUserFiles/v1/
NameValueTypeRequiredDescription
click to setstring Yes Access key
uint64 Yes Steam ID of the user whose files are being requested.
uint32 Yes App Id of the app that the files were published to.
uint32 NoShortcut Id to retrieve published files from.
uint32 NoStarting page for results.
uint32 NoThe number of results, per page to return.
string NoType of files to be returned.
string NoSorting method to use on returned values.
uint32 NoFilter by privacy settings.
string NoTags that must be present on a published file to satisfy the query.
string NoTags that must NOT be present on a published file to satisfy the query.
{message} Yes Required key-value tags to match on.
uint32 NoFile type to match files to.
uint32 Yes App Id of the app that published the files, only matched if specified.
string Yes Match this cloud filename if specified.
uint32 NoAllow stale data to be returned for the specified number of seconds.
ELanguage NoSpecifies the localized text to return. Defaults to English.
{message} NoAt least one of the tags must be present on a published file to satisfy the query.
{enum} NoFilter out items that have these content descriptors.
bool Yes Admin tool is doing a query, return hidden items
bool NoIf true, only return the total number of files that satisfy this query.
bool NoIf true, only return the published file ids of files that satisfy this query.
bool NoReturn vote data
bool Yes Return tags in the file details
bool NoReturn key-value tags in the file details
bool Yes Return preview image and video details in the file details
bool Yes Return child item ids in the file details
bool NoPopulate the short_description field instead of file_description
bool Yes Return pricing information, if applicable
bool NoPopulate the metadata field
uint32 Yes Return playtime stats for the specified number of days before today.
bool Yes Strips BBCode from descriptions.
bool NoIf true, then reactions to items will be returned.
uint32 Yes Backwards compatible for the client.
EPublishedFileRevision NoReturn the data for the specified revision.
bool Yes Return list of apps the items belong to

Get user vote summary

https://api.steampowered.com/IPublishedFileService/GetUserVoteSummary/v1/
NameValueTypeRequiredDescription
uint64[] Yes
UNDOCUMENTEDPOSTPublish

Publishes a clouded user file to the Workshop.

https://api.steampowered.com/IPublishedFileService/Publish/v1/
NameValueTypeRequiredDescription
click to setstring Yes Access key
uint32 NoApp Id this file is being published FROM.
uint32 NoApp Id this file is being published TO.
string NoName of the file to publish in the user's cloud.
string NoName of the file to use as the published file's preview.
string NoText title for the published file.
string NoText description for the published file.
uint32 No(EWorkshopFileType) Type of Workshop file to publish.
string NoShortcut name for the published file.
string NoUser's YouTube account username.
string NoVideo Id of a YouTube video for this published file.
uint32 No(ERemoteStoragePublishedFileVisibility) Visibility of the published file (private, friends, public, etc.)
string NoIf supplied, the resulting published file's Id is appended to the URI.
string[] NoArray of text tags to apply to the published file.
string NoType of collection the published file represents.
string NoType of game the published file represents.
string NoIf this represents a game, this is the URL to that game's page.

Performs a search query for published files

https://api.steampowered.com/IPublishedFileService/QueryFiles/v1/
NameValueTypeRequiredDescription
click to setstring Yes Access key
EPublishedFileQueryType Yes enumeration EPublishedFileQueryType in clientenums.h
uint32 Yes Current page
string Yes Cursor to paginate through the results (set to '*' for the first request). Prefer this over using the page parameter, as it will allow you to do deep pagination. When used, the page parameter will be ignored.
uint32 NoThe number of results, per page to return.
uint32 Yes App that created the files
uint32 Yes App that consumes the files
string Yes Tags to match on. See match_all_tags parameter below
string NoTags that must NOT be present on a published file to satisfy the query.
bool NoIf true, then items must have all the tags specified, otherwise they must have at least one of the tags.
string Yes Required flags that must be set on any returned items
string Yes Flags that must not be set on any returned items
string Yes Text to match in the item's title or description
uint32 Yes EPublishedFileInfoMatchingFileType
uint64 Yes Find all items that reference the given item.
uint32 Yes If query_type is k_PublishedFileQueryType_RankedByTrend, then this is the number of days to get votes for [1,7].
bool Yes If query_type is k_PublishedFileQueryType_RankedByTrend, then limit result set just to items that have votes within the day range given
uint32 NoAllow stale data to be returned for the specified number of seconds.
ELanguage NoLanguage to search in and also what gets returned. Defaults to English.
{message} Yes Required key-value tags to match on.
{message} NoAt least one of the tags must be present on a published file to satisfy the query.
{message} NoFilter to items created within this range.
{message} NoFilter to items updated within this range.
{enum} NoFilter out items that have these content descriptors.
bool Yes Admin tool is doing a query, return hidden items
bool NoIf true, only return the total number of files that satisfy this query.
bool NoIf true, only return the published file ids of files that satisfy this query.
bool Yes Return vote data
bool Yes Return tags in the file details
bool Yes Return key-value tags in the file details
bool Yes Return preview image and video details in the file details
bool Yes Return child item ids in the file details
bool Yes Populate the short_description field instead of file_description
bool Yes Return pricing information, if applicable
bool NoPopulate the metadata
uint32 Yes Return playtime stats for the specified number of days before today.
bool Yes By default, if none of the other 'return_*' fields are set, only some voting details are returned. Set this to true to return the default set of details.
bool Yes Strips BBCode from descriptions.
EPublishedFileRevision NoReturn the data for the specified revision.
bool NoIf true, then reactions to items will be returned.

Refresh the voting queue for the user

https://partner.steam-api.com/IPublishedFileService/RefreshVotingQueue/v1/
NameValueTypeRequiredDescription
click to setstring Yes Access key
uint32 Yes
uint32 Yes EPublishedFileInfoMatchingFileType
string Yes Include files that have all the tags or any of the tags if match_all_tags is set to false.
bool NoIf true, then files must have all the tags specified. If false, then must have at least one of the tags specified.
string Yes Exclude any files that have any of these tags.
uint32 Yes Desired number of items in the voting queue. May be clamped by the server
EPublishedFileRevision NoFilter to items that have data for the specified revision.

Sets the metadata for a developer on the published file

https://partner.steam-api.com/IPublishedFileService/SetDeveloperMetadata/v1/
NameValueTypeRequiredDescription
click to setstring Yes Access key
uint64 Yes
uint32 Yes
string Yes
UNDOCUMENTEDPOSTSubscribe

Subscribes the user to the published file

https://api.steampowered.com/IPublishedFileService/Subscribe/v1/
NameValueTypeRequiredDescription
click to setstring Yes Access key
uint64 No
uint32 No
int32 No
bool No
bool No
UNDOCUMENTEDPOSTUnsubscribe

Unsubscribes the user from the published file

https://api.steampowered.com/IPublishedFileService/Unsubscribe/v1/
NameValueTypeRequiredDescription
click to setstring Yes Access key
uint64 No
uint32 No
int32 No
bool No
UNDOCUMENTEDPOSTUpdate

Updates information about a published file.

https://api.steampowered.com/IPublishedFileService/Update/v1/
NameValueTypeRequiredDescription
click to setstring Yes Access key
uint32 NoApp Id this published file belongs to.
fixed64 NoPublished file id of the file we'd like update.
string NoTitle of the published file.
string NoDescription of the published file.
uint32 NoVisibility of the published file.
string[] NoSet of tags for the published file.
string NoFilename for the published file.
string NoPreview filename for the published file.
bool NoWhether this published file should have a spoiler tag attached to it.
uint32 NoIf this is an image file, you can specify the image width.
uint32 NoIf this is an image file, you can specify the image height.
int32 NoIf setting title & description, what language to set

Adds/updates/removes a UGC ban in the app

https://partner.steam-api.com/IPublishedFileService/UpdateAppUGCBan/v1/
NameValueTypeRequiredDescription
click to setstring Yes Access key
uint64 Yes
uint32 Yes
uint32 Yes
string Yes

Updates the ban status on the item

https://partner.steam-api.com/IPublishedFileService/UpdateBanStatus/v1/
NameValueTypeRequiredDescription
click to setstring Yes Access key
uint64 Yes
uint32 Yes
bool Yes
string Yes

Update the incompatible status on the item

https://partner.steam-api.com/IPublishedFileService/UpdateIncompatibleStatus/v1/
NameValueTypeRequiredDescription
click to setstring Yes Access key
uint64 Yes
uint32 Yes
bool Yes

Updates key/value tags for a published file

https://partner.steam-api.com/IPublishedFileService/UpdateKeyValueTags/v1/
NameValueTypeRequiredDescription
click to setstring Yes Access key
uint64 Yes
{message} Yes
{message} Yes
string Yes
string Yes
uint32 Yes

Updates tags on the published file

https://partner.steam-api.com/IPublishedFileService/UpdateTags/v1/
NameValueTypeRequiredDescription
click to setstring Yes Access key
uint64 Yes
uint32 Yes
string Yes
string Yes
ELanguage Yes

User wants to vote on the item

https://partner.steam-api.com/IPublishedFileService/Vote/v1/
NameValueTypeRequiredDescription
click to setstring Yes Access key
uint64 Yes
bool Yes