> ## Documentation Index
> Fetch the complete documentation index at: https://docs.optimism.io/llms.txt
> Use this file to discover all available pages before exploring further.

# op-proposer

> Canonical hub for op-proposer, the OP Stack output proposer, covering what it does, who runs it, and where its guides, reference, releases, source, and spec live.

op-proposer is the OP Stack's output proposer: the service that submits
output roots, claims about the L2 chain's state, to L1 so that withdrawals
can be proven against them.

## Overview

op-proposer queries its rollup node for an output root (a commitment to the
L2 state at a given block) and submits it to L1 on a configured interval. On
a chain running fault proofs, each proposal is a transaction to the
`DisputeGameFactory` that creates a new dispute game: a claim that stands
unless successfully challenged. By default op-proposer proposes only
finalized L2 state, because a proposal of state that does not hold true later
is an invalid claim that carries dispute game penalties. (A pre-fault-proof
proposal path still exists in the code but is effectively unused.)

It exists because proposals are how L1 learns about L2 state: withdrawals are
authenticated against resolved proposals, so a user proves a withdrawal
against a proposed output root and finalizes it once that proposal's dispute
game resolves in its favor. Without op-proposer, no new output roots reach L1
and withdrawals cannot be proven.

**Who runs it:** the chain operator, as one of the chain's core services. On
chains with permissioned fault proofs, only the designated
[proposer role](/op-stack/protocol/privileged-roles) can submit proposals;
with [permissionless fault proofs](/op-stack/fault-proofs/explainer) anyone
can propose, but the operator still runs op-proposer so proposals land
regularly.

## Get started

* [Spin up proposer](/chain-operators/tutorials/create-l2-rollup/op-proposer-setup):
  set up and configure op-proposer as part of standing up an OP Stack
  chain.

## How-tos

* [Migrating to permissionless fault proofs](/chain-operators/tutorials/migrating-permissionless):
  configure the dispute components and switch the respected game type.
* [Switch to Kona proofs](/chain-operators/guides/features/switching-to-kona-proofs):
  move a chain to Kona-based fault proofs, including updating the game type
  op-proposer creates.

## Configuration & flags reference

* [Proposer configuration](/chain-operators/guides/configuration/proposer):
  every configuration option and environment variable, plus the proposer
  policy constraints that govern what gets proposed and when.

## Releases

* [op-proposer release history](/releases/op-proposer)

## Source & spec links

* [Source: `op-proposer/`](https://github.com/ethereum-optimism/optimism/tree/develop/op-proposer)
  in the Optimism monorepo; its
  [README](https://github.com/ethereum-optimism/optimism/blob/develop/op-proposer/README.md)
  documents the proposal flow (with a sequence diagram), design principles,
  and failure modes.
* [L2 output root proposals specification](https://specs.optimism.io/protocol/proposals.html):
  the normative definition of output-root proposals.
* [Withdrawals specification](https://specs.optimism.io/protocol/withdrawals.html):
  how withdrawals are proven against proposals.