> For the complete documentation index, see [llms.txt](https://docs.force.xyz/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.force.xyz/perp-mechanics.md).

# Perp Mechanics

A Force perp is a linear contract, margined and settled in stablecoin, on a published rate. Most of the venue machinery is inherited from Hyperliquid: matching, order types, margining, liquidations and the funding calculation. What Force builds is the pricing.

Three prices matter, and they are not the same thing.

| Price        | What it is                                   | What it drives                                   |
| ------------ | -------------------------------------------- | ------------------------------------------------ |
| **Oracle**   | The reference rate, computed by Force        | Funding, and an input to the mark                |
| **Mark**     | A manipulation-resistant valuation           | Margin, liquidations, triggers, unrealised PnL   |
| **External** | The last rate an outside market actually set | The reference for pricing while markets are shut |

Read them in this order:

1. **Sessions**: the market never closes, the things underneath it do. Everything else follows from that.
2. **Oracle Price**: how the reference rate is computed in each session, with the formulae.
3. **Mark Price**: how the traded book and the oracle combine into the number your position is actually margined against.
4. **External Price** and **Funding**.


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