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obs-websocket 5.0.0 protocol reference

General Introduction

obs-websocket provides a feature-rich RPC communication protocol, giving access to much of OBS's feature set. This document contains everything you should know in order to make a connection and use obs-websocket's functionality to the fullest.

Design Goals

  • Abstraction of identification, events, requests, and batch requests into dedicated message types
  • Conformity of request naming using similar terms like Get, Set, Get[x]List, Start[x], Toggle[x]
  • Conformity of OBS data key names like sourceName, sourceKind, sourceType, sceneName, sceneItemName
  • Error code response system - integer corrosponds to type of error, with optional comment
  • Possible support for multiple message encoding options: JSON and MessagePack
  • PubSub system - Allow clients to specify which events they do or don't want to receive from OBS
  • RPC versioning - Client and server negotiate the latest version of the obs-websocket protocol to communicate with.

Table of Contents

Connecting to obs-websocket

Here's info on how to connect to obs-websocket

Connection steps

These steps should be followed precisely. Failure to connect to the server as instructed will likely result in your client being treated in an undefined way.

  • Initial HTTP request made to the obs-websocket server.

    • HTTP request headers can be used to set the websocket communication type. The default format is JSON. Example headers:
      • Content-Type: application/json
      • Content-Type: application/msgpack
    • If an invalid Content-Type is specified, the connection will be closed with WebSocketCloseCode::InvalidContentType after upgrade (but before Hello).

  • Once the connection is upgraded, the websocket server will immediately send an OpCode 0 Hello message to the client.

  • The client listens for the Hello and responds with an OpCode 1 Identify containing all appropriate session parameters.

    • If there is an authentication key in the messageData object, the server requires authentication, and the steps in Creating an authentication string should be followed.
    • If there is no authentication key, the resulting Identify object sent to the server does not require an authentication string.
    • The client determines if the server's rpcVersion is supported, and if not it provides its closest supported version in Identify.

  • The server receives and processes the Identify sent by the client.

  • Once identification is processed on the server, the server responds to the client with an OpCode 2 Identified.

  • The client will begin receiving events from obs-websocket and may now make requests to obs-websocket.

  • At any time after a client has been identified, it may send an OpCode 3 Reidentify message to update certain allowed session parameters. The server will respond in the same way it does during initial identification.

Connection Notes

  • If the Content Type is application/msgpack, all messages must be sent over binary. If it is application/json, all messages must be sent over text.
  • The obs-websocket server listens for any messages containing a request-type key in the first level JSON from unidentified clients. If a message matches, the connection is dropped with WebSocketCloseCode::UnsupportedProtocolVersion and a warning is logged.
  • If a message with a messageType is not recognized to the obs-websocket server, the connection is dropped with WebSocketCloseCode::UnknownMessageType.
  • At no point may the client send any message other than a single Identify before it has received an Identified. Doing so will result in the connection being dropped by the server with WebSocketCloseCode::NotIdentified.

Creating an authentication string

obs-websocket uses SHA256 to transmit authentication credentials. The server starts by sending an object in the authentication key of its Hello message data. The client processes the authentication challenge and responds via the authentication string in the Identify message data.

For this guide, we'll be using supersecretpassword as the password.

The authentication object in Hello looks like this (example):

{
    "challenge": "+IxH4CnCiqpX1rM9scsNynZzbOe4KhDeYcTNS3PDaeY=",
    "salt": "lM1GncleQOaCu9lT1yeUZhFYnqhsLLP1G5lAGo3ixaI="
}

To generate the authentication string, follow these steps:

  • Concatenate the websocket password with the salt provided by the server (password + salt)
  • Generate an SHA256 binary hash of the result and base64 encode it, known as a base64 secret.
  • Concatenate the base64 secret with the challenge sent by the server (base64_secret + challenge)
  • Generate a binary SHA256 hash of that result and base64 encode it. You now have your authentication string.

For real-world examples of the authentication string creation, refer to the obs-websocket client libraries listed on the README.

Enumerations

These are the enumeration definitions for various codes used by obs-websocket.

WebSocketOpCode Enum

enum WebSocketOpCode {
    Hello = 0,
    Identify = 1,
    Identified = 2,
    Reidentify = 3,
    Event = 5,
    Request = 6,
    RequestResponse = 7,
    RequestBatch = 8,
    RequestBatchResponse = 9,
};

WebSocketCloseCode Enum

enum WebSocketCloseCode {
    // Internal only
    DontClose = 0,
    // Reserved
    UnknownReason = 4000,
    // The requested `Content-Type` specified in the request HTTP header is invalid.
    InvalidContentType = 4001,
    // The server was unable to decode the incoming websocket message
    MessageDecodeError = 4002,
    // A data key is missing but required
    MissingDataKey = 4003,
    // A data key has an invalid type
    InvalidDataKeyType = 4004,
    // The specified `op` was invalid or missing
    UnknownOpCode = 4005,
    // The client sent a websocket message without first sending `Identify` message
    NotIdentified = 4006,
    // The client sent an `Identify` message while already identified
    AlreadyIdentified = 4007,
    // The authentication attempt (via `Identify`) failed
    AuthenticationFailed = 4008,
    // The server detected the usage of an old version of the obs-websocket protocol.
    UnsupportedRpcVersion = 4009,
    // The websocket session has been invalidated by the obs-websocket server.
    SessionInvalidated = 4010,
};

EventSubscriptions Enum

enum EventSubscription {
    // Set subscriptions to 0 to disable all events
    None = 0,
    // Receive events in the `General` category
    General = (1 << 0),
    // Receive events in the `Config` category
    Config = (1 << 1),
    // Receive events in the `Scenes` category
    Scenes = (1 << 2),
    // Receive events in the `Inputs` category
    Inputs = (1 << 3),
    // Receive events in the `Transitions` category
    Transitions = (1 << 4),
    // Receive events in the `Filters` category
    Filters = (1 << 5),
    // Receive events in the `Outputs` category
    Outputs = (1 << 6),
    // Receive events in the `Scene Items` category
    SceneItems = (1 << 7),
    // Receive events in the `MediaInputs` category
    MediaInputs = (1 << 8),
    // Receive all event categories
    All = (General | Config | Scenes | Inputs | Transitions | Filters | Outputs | SceneItems | MediaInputs),
    // InputVolumeMeters event (high-volume)
    InputVolumeMeters = (1 << 9),
    // InputActiveStateChanged event (high-volume)
    InputActiveStateChanged = (1 << 10),
    // InputShowStateChanged event (high-volume)
    InputShowStateChanged = (1 << 11),
};

Subscriptions are a bitmask system. In many languages, to generate a bitmask that subscribes to General and Scenes, you would do: subscriptions = ((1 << 0) | (1 << 2))

RequestStatus Enum

enum RequestStatus {
    Unknown = 0,

    // For internal use to signify a successful parameter check
    NoError = 10,

    Success = 100,

    // The `requestType` key is missing from the request data
    MissingRequestType = 203,
    // The request type is invalid (does not exist)
    UnknownRequestType = 204,
    // Generic error code (comment is expected to be provided)
    GenericError = 205,

    // A required request parameter is missing
    MissingRequestParameter = 300,
    // The request does not have a valid requestData object.
    MissingRequestData = 301,

    // Generic invalid request parameter message
    InvalidRequestParameter = 400,
    // A request parameter has the wrong data type
    InvalidRequestParameterDataType = 401,
    // A request parameter (float or int) is out of valid range
    RequestParameterOutOfRange = 402,
    // A request parameter (string or array) is empty and cannot be
    RequestParameterEmpty = 403,
    // There are too many request parameters (eg. a request takes two optionals, where only one is allowed at a time)
    TooManyRequestParameters = 404,

    // An output is running and cannot be in order to perform the request (generic)
    OutputRunning = 500,
    // An output is not running and should be
    OutputNotRunning = 501,
    // Stream is running and cannot be
    StreamRunning = 502,
    // Stream is not running and should be
    StreamNotRunning = 503,
    // Record is running and cannot be
    RecordRunning = 504,
    // Record is not running and should be
    RecordNotRunning = 505,
    // Record is paused and cannot be
    RecordPaused = 506,
    // Replay buffer is running and cannot be
    ReplayBufferRunning = 507,
    // Replay buffer is not running and should be
    ReplayBufferNotRunning = 508,
    // Replay buffer is disabled and cannot be
    ReplayBufferDisabled = 509,
    // Studio mode is active and cannot be
    StudioModeActive = 510,
    // Studio mode is not active and should be
    StudioModeNotActive = 511,
    // Virtualcam is running and cannot be
    VirtualcamRunning = 512,
    // Virtualcam is not running and should be
    VirtualcamNotRunning = 513,

    // The specified source (obs_source_t) was of the invalid type (Eg. input instead of scene)
    InvalidSourceType = 600,
    // The specified source (obs_source_t) was not found (generic for input, filter, transition, scene)
    SourceNotFound = 601,
    // The specified source (obs_source_t) already exists. Applicable to inputs, filters, transitions, scenes
    SourceAlreadyExists = 602,
    // The specified input (obs_source_t-OBS_SOURCE_TYPE_FILTER) was not found
    InputNotFound = 603,
    // The specified input (obs_source_t-OBS_SOURCE_TYPE_INPUT) had the wrong kind
    InvalidInputKind = 604,
    // The specified filter (obs_source_t-OBS_SOURCE_TYPE_FILTER) was not found
    FilterNotFound = 605,
    // The specified transition (obs_source_t-OBS_SOURCE_TYPE_TRANSITION) was not found
    TransitionNotFound = 606,
    // The specified transition (obs_source_t-OBS_SOURCE_TYPE_TRANSITION) does not support setting its position (transition is of fixed type)
    TransitionDurationFixed = 607,
    // The specified scene (obs_source_t-OBS_SOURCE_TYPE_SCENE), (obs_scene_t) was not found
    SceneNotFound = 608,
    // The specified scene item (obs_sceneitem_t) was not found
    SceneItemNotFound = 609,
    // The specified scene collection was not found
    SceneCollectionNotFound = 610,
    // The specified profile was not found
    ProfileNotFound = 611,
    // The specified output (obs_output_t) was not found
    OutputNotFound = 612,
    // The specified encoder (obs_encoder_t) was not found
    EncoderNotFound = 613,
    // The specified service (obs_service_t) was not found
    ServiceNotFound = 614,
    // The specified hotkey was not found
    HotkeyNotFound = 615,
    // The specified directory was not found
    DirectoryNotFound = 616,
    // The specified config item (config_t) was not found. Could be section or parameter name
    ConfigParameterNotFound = 617,
    // The specified property (obs_properties_t) was not found
    PropertyNotFound = 618,
    // The specififed key (OBS_KEY_*) was not found
    KeyNotFound = 619,
    // The specified data realm (OBS_WEBSOCKET_DATA_REALM_*) was not found
    DataRealmNotFound = 620,
    // The scene collection already exists
    SceneCollectionAlreadyExists = 621,
    // There are not enough scene collections to perform the action
    NotEnoughSceneCollections = 622,
    // The profile already exists
    ProfileAlreadyExists = 623,
    // There are not enough profiles to perform the action
    NotEnoughProfiles = 624,
    // There are not enough scenes to perform the action
    NotEnoughScenes = 625,

    // Processing the request failed unexpectedly
    RequestProcessingFailed = 700,
    // Starting the Output failed
    OutputStartFailed = 701,
    // Duplicating the scene item failed
    SceneItemDuplicationFailed = 702,
    // Rendering the screenshot failed
    ScreenshotRenderFailed = 703,
    // Encoding the screenshot failed
    ScreenshotEncodeFailed = 704,
    // Saving the screenshot failed
    ScreenshotSaveFailed = 705,
    // Creating the directory failed
    DirectoryCreationFailed = 706,
    // The combination of request parameters cannot be used to perform an action
    CannotAct = 707,
    // Creation of a new stream service failed
    StreamServiceCreationFailed = 708,
};

Message Types (OpCodes)

The following message types are the low-level message types which may be sent to and from obs-websocket.

Messages sent from the obs-websocket server or client may contain these first-level keys, known as the base object:

{
  "op": number,
  "d": object
}

Hello (OpCode 0)

  • Sent from: obs-websocket
  • Sent to: Freshly connected websocket client
  • Description: First message sent from the server immediately on client connection. Contains authentication information if auth is required. Also contains RPC version for version negotiation.

Data Keys:

{
  "obsWebSocketVersion": string,
  "rpcVersion": number,
  "authentication": object(optional)
}
  • rpcVersion is a version number which gets incremented on each breaking change to the obs-websocket protocol. Its usage in this context is to provide the current rpc version that the server would like to use.

Example Messages: Authentication is required

{
  "op": 0,
  "d": {
    "obsWebSocketVersion": "5.0.0",
    "rpcVersion": 1,
    "authentication": {
      "challenge": "+IxH4CnCiqpX1rM9scsNynZzbOe4KhDeYcTNS3PDaeY=",
      "salt": "lM1GncleQOaCu9lT1yeUZhFYnqhsLLP1G5lAGo3ixaI="
    }
  }
}

Authentication is not required

{
  "op": 0,
  "d": {
    "obsWebSocketVersion": "5.0.0",
    "rpcVersion": 1
  }
}

Identify (OpCode 1)

  • Sent from: Freshly connected websocket client
  • Sent to: obs-websocket
  • Description: Response to Hello message, should contain authentication string if authentication is required, along with PubSub subscriptions and other session parameters.

Data Keys:

{
  "rpcVersion": number,
  "authentication": string(optional),
  "ignoreInvalidMessages": bool(optional) = false,
  "ignoreNonFatalRequestChecks": bool(optional) = false,
  "eventSubscriptions": number(optional) = (EventSubscription::All)
}
  • rpcVersion is the version number that the client would like the obs-websocket server to use.
  • When ignoreInvalidMessages is true, the socket will not be closed for WebSocketCloseCode: MessageDecodeError, UnknownMessageType, or RequestMissingRequestId. Instead, the message will be logged and dropped.
  • When ignoreNonFatalRequestChecks is true, requests will ignore checks which are not critical to the function of the request. Eg calling DeleteScene when the target scene does not exist would still return RequestStatus::Success if this flag is enabled.
  • eventSubscriptions is a bitmask of EventSubscriptions items to subscribe to events and event categories at will. By default, all event categories are subscribed, except for events marked as high volume. High volume events must be explicitly subscribed to.

Example Message:

{
  "op": 1,
  "d": {
    "rpcVersion": 1,
    "authentication": "Dj6cLS+jrNA0HpCArRg0Z/Fc+YHdt2FQfAvgD1mip6Y=",
    "eventSubscriptions": 33
  }
}

Identified (OpCode 2)

  • Sent from: obs-websocket
  • Sent to: Freshly identified client
  • Description: The identify request was received and validated, and the connection is now ready for normal operation.

Data Keys:

{
  "negotiatedRpcVersion": number
}
  • If rpc version negotiation succeeds, the server determines the RPC version to be used and gives it to the client as negotiatedRpcVersion

Example Message:

{
  "op": 2,
  "d": {
    "negotiatedRpcVersion": 1
  }
}

Reidentify (OpCode 3)

  • Sent from: Identified client
  • Sent to: obs-websocket
  • Description: Sent at any time after initial identification to update the provided session parameters.

Data Keys:

{
  "ignoreInvalidMessages": bool(optional) = false,
  "ignoreNonFatalRequestChecks": bool(optional) = false,
  "eventSubscriptions": number(optional) = (EventSubscription::All)
}
  • Only the listed parameters may be changed after initial identification. To change a parameter not listed, you must reconnect to the obs-websocket server.

Event (OpCode 5)

  • Sent from: obs-websocket
  • Sent to: All subscribed and identified clients
  • Description: An event coming from OBS has occured. Eg scene switched, source muted.

Data Keys:

{
  "eventType": string,
  "eventData": object(optional)
}

Example Message:

{
  "op": 2,
  "d": {
    "eventType": "StudioModeStateChanged",
    "eventData": {
      "studioModeEnabled": true
    }
  }
}

Request (OpCode 6)

  • Sent from: Identified client
  • Sent to: obs-websocket
  • Description: Client is making a request to obs-websocket. Eg get current scene, create source.

Data Keys:

{
  "requestType": string,
  "requestId": string,
  "requestData": object(optional),
  
}

Example Message:

{
  "op": 6,
  "d": {
    "requestType": "SetCurrentScene",
    "requestId": "f819dcf0-89cc-11eb-8f0e-382c4ac93b9c",
    "requestData": {
      "sceneName": "Scene 12"
    }
  }
}

RequestResponse (OpCode 7)

  • Sent from: obs-websocket
  • Sent to: Identified client which made the request
  • Description: obs-websocket is responding to a request coming from a client.

Data Keys:

{
  "requestType": string,
  "requestId": string,
  "requestStatus": object,
  "responseData": object(optional)
}
  • The requestType and requestId are simply mirrors of what was sent by the client.

requestStatus object:

{
  "result": bool,
  "code": number,
  "comment": string(optional)
}
  • result is true if the request resulted in RequestStatus::Success. False if otherwise.
  • code is a RequestStatus code.
  • comment may be provided by the server on errors to offer further details on why a request failed.

Example Messages: Successful Response

{
  "op": 7,
  "d": {
    "requestType": "SetCurrentScene",
    "requestId": "f819dcf0-89cc-11eb-8f0e-382c4ac93b9c",
    "requestStatus": {
      "result": true,
      "code": 100
    }
  }
}

Failure Response

{
  "op": 7,
  "d": {
    "requestType": "SetCurrentScene",
    "requestId": "f819dcf0-89cc-11eb-8f0e-382c4ac93b9c",
    "requestStatus": {
      "result": false,
      "code": 608,
      "comment": "Parameter: sceneName"
    }
  }
}

RequestBatch (OpCode 8)

  • Sent from: Identified client
  • Sent to: obs-websocket
  • Description: Client is making a batch of requests for obs-websocket. Requests are processed serially (in order) by the server.

Data Keys:

{
  "requestId": string,
  "haltOnFailure": bool(optional) = false,
  "requests": array<object>
}
  • When haltOnFailure is true, the processing of requests will be halted on first failure. Returns only the processed requests in RequestBatchResponse.
  • Requests in the requests array follow the same structure as the Request payload data format, however requestId is an optional key.

RequestBatchResponse (OpCode 9)

  • Sent from: obs-websocket
  • Sent to: Identified client which made the request
  • Description: obs-websocket is responding to a request batch coming from the client.

Data Keys:

{
  "requestId": string,
  "results": array<object>
}

Requests/Events Table of Contents

Events

Requests