Sessions

session.start

Starts a game for one player. Returns a session and a game link.

Who calls it

You → usPOST /v1/session.start

The player taps a game. Your server calls this. Sign the call with your API key. See Authentication.

Request

Field	Type	What it is
`requestId`	string	Your id for this change. Send it again after a timeout and you get the first answer back.
`firstSentAt`	string, UTC time	When you first sent this request. It stays the same on every retry. A request older than 7 days is refused.
`playerId`	string	Your id for the player. We send it back in every wallet call, so you know whose balance to use.
`casinoSessionId`	string	Your own session. We send it back in every wallet call and event.
`gameId`	string	Which game to open.
`currency`	string	Which money the wallet calls use, and how the game shows amounts.
`language`	string	The game’s words in the player’s language. A language we do not have falls back to English.
`market`	string	Required: UK, SE or none. Only for rules the game itself must follow in that market. It is required, so a forgotten field can’t switch off a law.
`betSettings`	object	Min, max and default bet for this player. See Bet settings.
`exitUrl`	string, optional	Where the exit button goes when you can’t get client messages: a full browser page, or a Unity app that opens the browser.

Answer

Field	Type	What it is
`sessionId`	string	You need it to close the session. You find it in every wallet call.
`url`	string	The game link. Open it to show the game.
`linkExpiresAt`	string, UTC time	When the link stops working (2 minutes). Do not open a link that has expired, for example one from a late retry.

The balance is not in the answer. Our server asks your wallet when the game opens. The bet settings are not in the answer: you already have them. They are in session.get.

The game link

The link works once. The first open uses it up. Refresh in the same page works.
Any other open (another browser, a copied link) shows “This game link was already used.” Start a new session.
The link must be opened within 2 minutes. If it is not, the session closes as not_opened.
A copied link can’t be used to play with your player’s money.
A retry of session.start can return a link that has already expired. Check linkExpiresAt, then start a new session with a new requestId.
An app whose web view was killed starts a new session. See Events.

Errors

Code	When	Your next step
`invalid_request`	A field is missing or wrong, for example a firstSentAt more than 5 minutes in the future. message names the field.	Fix the call. Sending it again unchanged fails again.
`request_expired`	firstSentAt is older than 7 days. Nothing is done.	A bug or a stuck job on your side. Look up the result with session.get or round.get.
`duplicate_mismatch`	A requestId we have seen comes with a different body.	A bug on your side: each new change needs a new id.
`game_not_found`	No game with this gameId for your account.	Pull games.list again.
`game_disabled`	The game is turned off in the back office.	Hide the game. A player with an open Mines round can still start it.
`bet_settings_invalid`	min is above max, default is outside them, or a value is 0 or less.	Fix the bet settings.
`currency_not_supported`	The currency is not set up for your account.	Set it up in the back office, or use another currency.

Every call can also return the codes that guard all calls. See Error codes.

Example

POST /v1/session.startExample

Request
{
  "requestId": "rq-77120",
  "firstSentAt": "2026-10-31T09:02:10Z",
  "playerId": "p-82731",
  "casinoSessionId": "c-5531",
  "gameId": "mines",
  "currency": "EUR",
  "language": "en",
  "market": "UK",
  "betSettings": { "min": 10, "max": 10000, "default": 100 },
  "exitUrl": "https://casino.example/lobby"
}

Answer
{
  "ok": true,
  "result": {
    "sessionId": "s-01JC8Z…",
    "url": "https://play.nartifacts.com/s/s-01JC8Z…",
    "linkExpiresAt": "2026-10-31T09:04:10Z"
  },
  "traceId": "tr-01JC…"
}

Previous← Bet settings Nextsession.updateBetSettings →