What do GTC, IOC and ALO mean on Hyperliquid?
GTC, IOC and ALO are time-in-force choices for a limit order on Hyperliquid: they set what happens when the order first reaches the book. GTC (good till cancelled) rests until filled or cancelled. IOC (immediate or cancel) fills what it can at once and cancels the rest. ALO (add liquidity only) only rests, and is cancelled if it would fill at once.
- Time in force belongs to a limit order and decides what happens when it first reaches the order book.
- GTC, good till cancelled: fills what it can at once and leaves the rest resting on the book until it fills or is cancelled.
- IOC, immediate or cancel: fills what it can at once, and the unfilled part is cancelled instead of resting.
- ALO, add liquidity only, also called post only: cancelled instead of filling at once, so it only ever fills as a resting order and pays the maker fee.
- In the example, GTC and IOC both buy 4 at once. GTC leaves 6 resting, IOC cancels them, and an ALO at the same price is cancelled whole.
What time in force means
A limit order names the worst price you will accept. Its time in force says how long it may live. Hyperliquid’s docs put it this way: time in force sets the behaviour of the order upon first hitting the book.
The difference between the three only shows when part of an order cannot fill at once, or when its price would fill at once. An order whose price is nowhere near the market rests under GTC and ALO alike; under IOC it is cancelled.
GTC: good till cancelled
A GTC order fills what it can at once, at its price or better, and the rest stays on the book until it fills or is cancelled. Hyperliquid’s docs say GTC orders have no special behaviour: it is the plain limit order.
The part that fills at once pays the taker fee. The part that rests and fills later pays the maker fee. Maker and taker explains the two. A resting order waits until something ends it, so one placed for a reason that has passed can still fill later.
IOC: immediate or cancel
An IOC order fills what it can at once, at its price or better, and the unfilled part is cancelled instead of resting. It never waits on the book, so it never pays the maker fee and never leaves an order behind.
That makes it a fill now with a cap on the price: nothing beyond the limit, and nothing left over. The cost is that it may fill only in part, or not at all, when little is offered at the price.
ALO: add liquidity only
An ALO order, which Hyperliquid also lists as Post Only, is added to the book but does not fill on arrival. If its price would match a resting order straight away, it is cancelled instead. It is only executed as a resting order, so every fill pays the maker fee.
So a post-only buy has to sit below the best offer, and a post-only sell above the best bid. Placed where it would cross, it is cancelled whole and nothing fills. That cancel is the order doing its job, not an error.
On Hyperliquid
Hyperliquid’s order types list GTC, Post Only (ALO) and IOC as the time-in-force options for a limit order, and every limit order sent to it carries one of the three.
In BuildTrade™, a Limit order from the order ticket is sent as GTC: any part that does not fill at once rests on the book and is listed in Open Orders until it fills or you cancel it. The ticket has no IOC or ALO choice.
One limit buy, four ways
Example numbersA limit buy of 10 units at 100.01, where 4 units are offered at that price and nothing lower. The last line is the same post-only buy placed at 100.00, below the offer.
- Order size, units
- 10
- Limit price
- 100.01
- Units offered at that price
- 4
- GTC, filled at once
- 4
- GTC, left resting
- 6
- IOC, filled at once
- 4
- IOC, cancelled
- 6
- ALO at the same price, cancelled
- 10
- ALO below the offer, resting
- 10
GTC and IOC fill the same 4 units and part ways over the other 6: GTC leaves them on the book at 100.01, IOC cancels them. ALO never takes, so at a price that would fill at once it is cancelled whole, and below the offer it waits as a maker.
Mistakes that cost traders money
- Leaving a GTC order behind.
A GTC order rests until it fills or is cancelled. One placed for a reason that has passed can still fill much later.
- Expecting IOC to fill in full.
IOC fills only what is offered at its price or better. The rest is cancelled, so the position can come out smaller than planned.
- Placing ALO where it would cross.
A post-only buy at or above the best offer is cancelled instead of filling, and nothing reaches the book.
- Reading a cancelled ALO as a fault.
The cancel is the point: ALO refuses to take, so it never pays the taker fee.
- Thinking time in force changes the price.
All three respect the limit price. Time in force only decides what happens on arrival to the part that can or cannot fill.
Try it in BuildTrade™
Open the Book tab on the Trade screen and read the best offer and the size offered at it. A limit buy at that price for more than that size would fill that much at once; what happens to the rest is the time-in-force choice.
Order types, Hyperliquid Docs (read October 20, 2026).
Exchange endpoint, Hyperliquid Docs (read October 20, 2026).
BuildTrade™ is independent of, and not endorsed by, Hyperliquid.