Order types and time in force

Every order answers two questions: the worst price you accept, and what happens to the part that can’t fill at once. The second sets your fee: taking resting liquidity pays the taker rate; resting and filling later pays the lower maker rate or earns a rebate (fees).

Time in force decides what happens on arrival

Every order is a price, a size, a side and a time in force (TIF):

Order	TIF on the wire	On arrival	Unfilled part	Fee
Limit, good til cancelled	Gtc	Fills against anything at its price or better	Rests until filled or cancelled	Taker on what fills at once, maker on the rest
Immediate or cancel	Ioc	Same	Cancelled; fills already made stay	Taker
Post only (add liquidity only)	Alo	Cancelled if it would match anything	Rests; can only fill as a maker	Maker
Market	FrontendMarket	Fills against the book up to a worst price	Does not rest	Taker

Say the best ask is 100 with 5 on offer, and you buy 8 at 100. A Gtc fills 5 as taker and rests 3 as maker; an Ioc fills 5 and cancels 3; an Alo is cancelled outright.

• Market orders are not native: each is a limit order with TIF FrontendMarket and a worst price from the app’s slippage setting (one production app uses 3 per cent from the mark price).
• Reduce-only is a flag, not a TIF. It is rejected if it would increase the position, and cancelled if it rests and stops reducing.
• No fill-or-kill or good-til-date. Ioc keeps partial fills. expiresAfter only stops a delayed action landing late; the dead man’s switch cancels all open orders at a set time (orders).
• Block ordering: actions sending no Gtc or Ioc order (post-only among them), then cancels, then Gtc and Ioc. A post-only or cancel beats a taker in the same block (the order book).

Stops, take profits, trailing stops, TWAP, scale and chase orders all end as one of these (TP/SL, TWAP and scale).

The numbers

Parameter	Value
TIF values in the order action	Gtc, Ioc, Alo, FrontendMarket
TIF codes from a HyperEVM contract (CoreWriter action 1)	1 Alo, 2 Gtc, 3 Ioc; no FrontendMarket
Minimum order value	$10 on perps; 10 units of the quote token on spot
Price	at most 5 significant figures and at most 6 - szDecimals decimals (perps) or 8 - szDecimals (spot); integer prices always allowed
Size	rounded to the asset’s szDecimals
Maximum market order value, perps	$30,000,000 at max leverage 25 or more; $5,000,000 at 20 to 24; $2,000,000 at 10 to 19; $500,000 below 10
Maximum limit order value, perps	10 x the maximum market order value

Choosing the right order

• Gtc limit: you have a price and can wait.
• Post only: maker rate or rebate, never taker. If the market moved through your price, it’s cancelled.
• Market: the fill matters more than the price. In a thin book, prefer an Ioc at your own worst price.
• Reduce-only on every exit: a repeated or delayed close cannot flip you.

Sending an order from code

{
  "type": "order",
  "orders": [{
    "a": 0,
    "b": true,
    "p": "95000",
    "s": "0.001",
    "r": false,
    "t": { "limit": { "tif": "Alo" } }
  }],
  "grouping": "na"
}

a is the asset id, b buy, p and s decimal strings, r reduce-only. A market order sets "tif": "FrontendMarket" and p to the worst price. Each order gets its own statuses entry:

Error string	Cause
“Post only order would have immediately matched, bbo was …”	Alo would have crossed
“Order could not immediately match against any resting orders.”	Ioc found nothing
“Reduce only order would increase position.”	r: true on an order that adds to the position
“Order must have minimum value of $10.”	below the minimum notional
“No liquidity available for market order.”	market order into an empty side
“Price must be divisible by tick size.”	price precision

• Payload errors (empty batch, TP/SL not reduce-only, price too far from the reference price) come back once per batch.
• From a HyperEVM contract (CoreWriter action 1), a market order is an Ioc with a worst price; limitPx and sz are 1e8 x the human value (CoreWriter).

FrontendMarket, upgrades and empty Ioc fills

The official docs differ

The exchange endpoint docs list only Alo, Ioc and Gtc. The info endpoint’s own examples return "orderType": "Market" with "tif": "FrontendMarket", and the SDKs send it. Use FrontendMarket for market orders over the HTTP API.

• Market orders do not fill during a network upgrade’s post-only period.
• An Ioc that matches nothing returns an error status, not an empty fill.

For every order field and response, see Orders. For what happens when your order meets your own, see Self-trade prevention.