Market symbols

Every market carries a symbol: a short, readable name that says which event it belongs to and which outcome it settles on. An event is one scheduled game, the same thing event_id and event_start refer to.

STXMLB-26AUG271305COLWSH-GAMEWSH

That is the Washington Nationals to beat the Colorado Rockies, in the MLB game starting 27 August 2026 at 13:05.

The market_id is a UUID and tells you nothing on its own. STX identifies the exchange, and every segment after it is derived from the event (the competition, the start time, the two teams, and the outcome the contract settles on), all of which you already know if you track the game at all.

So the symbol is predictable rather than assigned. Given a game you already follow, you can construct the symbol you expect and match it against ours, instead of calling the API to discover which market_id corresponds to which game.

Anatomy

A symbol has two halves, joined by a hyphen.

STXMLB-26AUG271305COLWSH  -  GAMEWSH
└────── event symbol ────┘    └ market ┘

The event symbol identifies the event, and every market on the same game shares it. The market segment identifies what this particular market is asking, which part of the game it settles over, and which side of it you are buying.

STXMLB-26SEP032210STLLAD-TOTAL8.5      full game
STXMLB-26SEP032210STLLAD-R1TOTAL0.5    first inning, same game

To collect every market on a game, event_id is the field to group on: it is a UUID and needs no string handling. See Which identifier to use.

Written out in full:

{PREFIX}{COMPETITION}-{YYMONDDHHMM}{AWAY}{HOME}-{SCOPE}{TYPE}{SELECTION}

Segment	Example	What it is
Prefix	STX	Identifies the exchange. The only segment not derived from the event.
Competition	MLB	The league or competition code.
Date and time	26AUG271305	YYMONDDHHMM, from the event’s start time.
Away	COL	The away team, first.
Home	WSH	The home team, second.
Scope	R1	The part of the game the market settles over. Absent for a full-game market, which is most of them.
Type	GAME	What the market asks.
Selection	WSH	The outcome the contract pays on.

Away always precedes home, the usual way a matchup is written.

The date is in US Eastern

26AUG271305 is 27 August 2026, 13:05 US Eastern, the exchange’s clock. Not UTC, not the venue’s local time, and not whatever your pricing feed publishes: a LaLiga match in Spain and an MLB game in Los Angeles are both stamped Eastern.

The event_start field on the market is the UTC timestamp for the same moment, so convert before comparing the two, or a game near midnight Eastern will look like the wrong day.

Scope

Markets covering part of a game carry a scope code at the front of the market segment, before the type. A symbol with no scope code covers the full game, which is most of them.

STXMLB-26AUG281840LADDET-R1TOTAL0.5    MLB LAD @ DET OU 0.5, 1st inning
STXEPL-26AUG281500MNCCRY-R1TOTAL2.5    EPL MNC @ CRY OU 2.5, 1st half
STXMLB-26AUG281840LADDET-TOTAL8.5      MLB LAD @ DET OU 8.5, full game

There are two codes, F for first and R for range.

Code	Window	Example
F{n}	Periods 1 through n.	F5, the first five innings
R{a}T{b}	Periods a through b, inclusive. T reads as to.	R1T3, innings one to three
R{a}	Period a alone; the shorthand for R{a}T{a}.	R1, the first inning

Both count periods from 1, so F{n} and R1T{n} are the same window but the shorthand is preferred over R{a}T{a}.

A scope code is not a fixed duration. The two symbols above carry the same R1, but it means the first inning in baseball and the first half in soccer: the first scoring period of whatever sport the competition belongs to. Read it against the competition, never on its own.

The rules field carries the scope as a suffix (over_under_r1 for both markets above), so if you need to know a market’s scope in code, read rules rather than parsing it back out of the symbol.

Telling a scope from a type

The scope code is not padded to a fixed width. A type code never begins with F or R followed by a digit, so a market segment is scoped if and only if it opens with that pattern.

The scope runs to the end of the pattern (F{n}, R{a} or R{a}T{b}), and the type begins immediately after.

TOTAL8.5             no scope, type TOTAL, line 8.5
R1TOTAL0.5           scope R1, type TOTAL, line 0.5
R1T3TOTAL0.5         scope R1T3, type TOTAL, line 0.5
F5SPREADKCPLUS9.5    scope F5, type SPREAD, selection KCPLUS9.5

The rules field gives the scope directly.

Market types

The type segment tells you what is being asked.

Type	Market	Selection format
GAME	Winner	The winning team, WSH
GAMEREG	Winner in regulation	The winning team
GAME2W	Winner, two-way	The winning team
GAME3W	Winner, three-way	The winning team
DRAW	Draw	{AWAY}{HOME}
SPREAD	Handicap	{HOME}PLUS{line} or {HOME}MINUS{line}
TOTAL	Over/under	The line, 227.5
MATCH	Tennis match winner	The player
CHAMP	Championship	The team
WS	World Series	The team
LEAGUE	League winner	The team
CONF	Conference winner	The team
DIV	Division winner	The team

New market types arrive from time to time and take a code derived from the rule that created them, so treat this as the set in use today rather than a closed list. Match the types you recognize and fall through gracefully on one you do not. No type code begins with F or R followed by a digit; see Telling a scope from a type.

A spread on the home team at −7.5 reads:

STXNBA-26APR051900CHAMIN-SPREADMINMINUS7.5

Player props

Player markets use the stat code as the type, then the player and the line:

{STAT}{TEAM}{INITIAL}{LASTNAME}{JERSEY}-{LINE}

A points line in a Memphis at Milwaukee game:

STXNBA-26APR051500MEMMIL-PTSMILMTURNER3-12.5

Two things to know before you parse one:

• {TEAM} is the home team of the game, not the player’s team. Take the player’s team from participants rather than from the symbol.
• The line is separated by a hyphen, so a player-prop symbol has four hyphen-separated fields where other markets have three. Match the segments you need rather than splitting on every hyphen.

Stat codes vary by sport: PTS, REB, AST and 3PT in basketball, PASSYDS, RUSHTD and SACK in football, HR, RBI and SB in baseball.

Futures

Season markets are not tied to a single game, so the event symbol carries the competition and date without a participants segment:

{PREFIX}{COMPETITION}-{YYMONDDHHMM}

The market segment then names the team, as in a CHAMP or DIV market.

Combination markets

Combos are built from their legs rather than from a single game:

STXCOMBO-{EVENT_HASH}-{MARKET_HASH}

Each hash is derived from the symbols of the legs it combines. The same legs always produce the same symbol, in any order, so an identical combo is recognizable as one wherever you meet it.

Custom markets

Some markets do not belong to a scheduled game: a team making the playoffs, a tournament winner. They keep the same three-segment shape, but the middle segment is a label written when the market is created rather than a start time and two teams:

STXMLB-PLAYOFFSTOR-TOR            Toronto to make the playoffs
STXPGA-TOURCHAMPIONSHIP-LA        Ludvig Aberg to win the Tour Championship

So the prefix and competition still mean what they mean, and the last segment is still the selection. Only the middle segment is free text, which means you cannot parse a date or teams out of it. Check whether it matches {YYMONDDHHMM} before assuming it is a scheduled game.

Use rules and specifier to see what a custom market settles on, exactly as you would for a generated one.

Which identifier to use

Every market carries several identifiers, and they do different jobs.

Field	Use it for
market_id	The key in your own store, and the value you send back to us. A UUID, fixed for the life of the market. Every order, cancel and channel topic takes it.
event_id	Grouping a book by game. A UUID every market on the game shares, and the safest thing to group on, since it needs no string handling.
rules	What kind of market this is, in machine-readable form: home_winner, spread, player_stat_line. Scoped markets append the scope, as in over_under_r1.
specifier	The strike: the line, the handicap, the player.
participants	Team and player identity, with abbreviation, name and role given separately.
symbol	Mapping to markets you already track, matching against another venue, logs, dashboards, anything a person reads.

For mapping, the pair worth leaning on is rules and specifier. Between them they say exactly what a market asks and at what strike, in fields meant for code, while event_id and participants supply the event and the teams. That combination is more precise than parsing a symbol, and it does not require a team-code dictionary.

Symbols are rebuilt from the event they belong to, so read the current value from the API rather than treating a stored one as a key. Keep market_id alongside whatever you match on and you can act on a market immediately, without resolving it again.

Finding a market

GET /api/v1/markets returns symbol on every market, alongside market_id, event_id and the participants. Filter by competition and status to narrow the set:

GET /api/v1/markets?competitions=MLB&status=open

Then match on the symbol, or read event_id off any market and collect every market that shares it.

event_id is the better of the two for grouping a game’s book: it is a UUID, so it needs no string handling and cannot be thrown off by a change to the symbol format. Building the event symbol and matching on its prefix (matching STXMLB-26SEP032210STLLAD- to collect that game) does work, and picks up scoped markets along with full-game ones.

The markets WebSocket channel carries the symbol too, so a live client can map new markets as they appear without a REST call.

The order book channel accepts a symbol in place of the id, which is the one place a symbol addresses a market directly:

["1", "1", "market:STXMLB-26AUG271305COLWSH-GAMEWSH", "phx_join", {}]

See WebSocket channels for the frame format.