> ## 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.

# Running an archive node

> Learn how to configure and run an archive node.

This guide shows you how to configure your node to run as an archive node. Archive nodes store the complete history of the blockchain, including all historical states.

## Overview

Archive nodes maintain the entire state history of the blockchain, allowing you to query any historical state at any block height. This is useful for:

* Block explorers that need to provide historical data
* Analytics and data analysis applications
* Services that need to query historical state
* Debugging and auditing purposes

Archive nodes use execution-layer sync but configure the execution client to retain all historical state data instead of pruning it.

## Requirements

* **OP Mainnet**: Requires the [bedrock datadir](/node-operators/guides/management/snapshots)
* **Other OP Stack networks**: No datadir required
* **Storage**: Archive nodes require significantly more disk space than regular nodes (several terabytes for OP Mainnet)
* **Sync time**: Archive sync with execution-layer mode is faster than full block-by-block execution

## Configuration

### Configuration for op-node

Set the following flag on `op-node`:

```shell theme={null}
--syncmode=execution-layer
```

<Info>
  The `--syncmode=execution-layer` flag is not the default setting and must be explicitly configured.
</Info>

### Configuration for op-geth

Set the following flags on `op-geth`:

```shell theme={null}
--syncmode=full
--gcmode=archive
```

<Info>
  Both flags are not the default settings and must be explicitly configured. The `--syncmode=full` flag ensures every block is executed, and `--gcmode=archive` disables state pruning.
</Info>

### Configuration for Nethermind

Archive sync can be enabled by using the archive configuration for your network (configurations with `_archive` suffix):

```shell theme={null}
--config op-mainnet_archive
```

<Info>
  Replace `op-mainnet_archive` with the appropriate archive configuration for your network (e.g., `op-sepolia_archive` for OP Sepolia).
</Info>

## Archive mode with alternative clients

Alternative execution clients such as `reth` and `op-erigon` are designed as archive nodes by default, which means they always maintain the complete history of the chain. When using these clients with execution-layer sync, they will automatically operate in archive mode.

### Configuration for op-node with reth

Set the following flags on `op-node`:

```shell theme={null}
--syncmode=execution-layer
--l2.enginekind=reth
```

<Info>
  Both flags are not the default setting and must be explicitly configured on `op-node`. `reth` operates as an archive node by default.
</Info>

### Configuration for op-node with op-erigon

Set the following flags on `op-node`:

```shell theme={null}
--syncmode=execution-layer
--l2.enginekind=erigon
```

<Info>
  Both flags are not the default setting and must be explicitly configured on `op-node`. `op-erigon` operates as an archive node by default.
</Info>

## How archive sync works

With execution-layer sync mode enabled:

1. **Initial sync**: The node downloads block headers and data through the P2P network
2. **Block execution**: The node executes every block in the chain to build the complete state history
3. **State retention**: Unlike regular nodes, archive nodes never prune historical state data
4. **Faster than legacy**: While still executing all blocks, this is faster than the legacy consensus-layer sync because block data is retrieved via P2P instead of being derived from L1

## Storage considerations

Archive nodes require substantial storage:

* **OP Mainnet**: Several terabytes and growing
* **Other networks**: Varies by network age and activity
* **Growth rate**: Storage requirements increase continuously as new blocks are added
* **Recommendation**: Use fast SSD storage for optimal performance

## Next steps

* See the [Snap Sync guide](/node-operators/guides/management/snap-sync) for non-archive node configuration
* See the [Consensus Client Configuration](/node-operators/guides/configuration/consensus-clients) and [Execution Client Configuration](/node-operators/guides/configuration/execution-clients) guides for additional explanation or customization
* See the [Snapshots guide](/node-operators/guides/management/snapshots) for information about downloading the bedrock datadir
* If you experience difficulty at any stage of this process, please reach out to [developer support](https://github.com/ethereum-optimism/developers/discussions)