---
title: "shared"
description: "Foundational crates for primitives, access lists, JWT auth, bundles, CLI utilities, and RPC types."
source: https://basehub.org/crates/shared/overview/
---
The `shared` crate group holds the foundational types and utilities used across the workspace. It defines primitives, access lists, JWT auth, and RPC extensions consumed by every other crate group.

## Sub-crates

| Crate | Package Name | Purpose |
|-------|-------------|---------|
| [access-lists](/crates/shared/access-lists/) | `base-access-lists` | Flashblock-level Access Lists (FAL) implementation |
| [bundles](/crates/shared/bundles/) | `base-bundles` | Transaction bundle types |
| [cli-utils](/crates/shared/cli-utils/) | `base-cli-utils` | CLI utilities (logging, metrics, clap helpers) |
| [engine-ext](/crates/shared/engine-ext/) | `base-engine-ext` | Engine API extensions |
| [jwt](/crates/shared/jwt/) | `base-jwt` | JWT authentication for Engine API |
| [node](/crates/shared/node/) | `base-client-node` | Shared node configuration |
| [primitives](/crates/shared/primitives/) | `base-primitives` | Core primitive types (includes Solidity contracts for tests) |
| [reth-rpc-types](/crates/shared/reth-rpc-types/) | `base-reth-rpc-types` | Reth-compatible RPC type definitions |
| [txpool-rpc](/crates/shared/txpool-rpc/) | `base-txpool-rpc` | Transaction pool RPC extensions |

## Role in the Architecture

The shared crates form the foundation layer that all other crate groups depend on:

- **primitives** — Defines the core types (transactions, blocks, receipts) used everywhere. Includes Solidity contracts compiled with Foundry for testing.
- **access-lists** — Implements the [FAL specification](/specifications/access-lists/) for flashblock-level access lists, adapting EIP-7928 for the OP Stack.
- **cli-utils** — Provides standardized CLI setup including clap argument parsing, tracing/logging configuration, and Prometheus metrics exporting.
- **jwt** — Handles JWT-based authentication for the Engine API connection between execution and consensus layers.
- **engine-ext** — Extends the Engine API with Base-specific payload attributes.
- **txpool-rpc** — Adds custom RPC methods for interacting with the transaction pool.
- **bundles** — Defines transaction bundle types for MEV and priority ordering.
- **reth-rpc-types** — Bridges Base types to Reth's RPC type system.

## Source

[`crates/shared/`](https://github.com/base/base/tree/main/crates/shared)