![Zebra logotype](https://www.zfnd.org/images/zebra-logotype.png)

---

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## Contents

- [Contents](#contents)
- [About](#about)
- [Beta Releases](#beta-releases)
- [Getting Started](#getting-started)
- [Known Issues](#known-issues)
- [Future Work](#future-work)
- [Documentation](#documentation)
- [Security](#security)
- [License](#license)

## About

[Zebra](https://zebra.zfnd.org/) is the Zcash Foundation's independent,
consensus-compatible implementation of a Zcash node, currently under
development. It can be used to join the Zcash peer-to-peer network, which helps
keeping Zcash working by validating and broadcasting transactions, and maintaining
the Zcash blockchain state in a distributed manner.
Please [join us on Discord](https://discord.gg/na6QZNd) if you'd
like to find out more or get involved!

Zcash is a cryptocurrency designed to preserve the user's privacy. Like most
cryptocurrencies, it works by a collection of software nodes run by members of
the Zcash community or any other interested parties. The nodes talk to each
other in peer-to-peer fashion in order to maintain the state of the Zcash
blockchain. They also communicate with miners who create new blocks. When a
Zcash user sends Zcash, their wallet broadcasts transactions to these nodes
which will eventually reach miners, and the mined transaction will then go
through Zcash nodes until they reach the recipient's wallet which will report
the received Zcash to the recipient.

The original Zcash node is named `zcashd` and is developed by the Electric Coin
Company as a fork of the original Bitcoin node. Zebra, on the other hand, is
an independent Zcash node implementation developed from scratch. Since they
implement the same protocol, `zcashd` and Zebra nodes can communicate with each
other and maintain the Zcash network interoperably.

If you just want to send and receive Zcash then you don't need to use Zebra
directly. You can download a Zcash wallet application which will handle that
for you. (Eventually, Zebra can be used by wallets to implement their
functionality.) You would want to run Zebra if you want to contribute to the
Zcash network: the more nodes are run, the more reliable the network will be
in terms of speed and resistance to denial of service attacks, for example.

These are some of the advantages or benefits of Zebra:

- Better performance: since it was implemented from scratch in an async, parallelized way, Zebra
  is currently faster than `zcashd`.
- Better security: since it is developed in a memory-safe language (Rust), Zebra
  is less likely to be affected by memory-safety and correctness security bugs that
  could compromise the environment where it is run.
- Better governance: with a new node deployment, there will be more developers
  who can implement different features for the Zcash network.
- Dev accessibility: supports more developers, which gives new developers
  options for contributing to Zcash protocol development.
- Runtime safety: with an independent implementation, the detection of consensus bugs
  can happen quicker, reducing the risk of consensus splits.
- Spec safety: with several node implementations, it is much easier to notice
  bugs and ambiguity in protocol specification.
- User options: different nodes present different features and tradeoffs for
  users to decide on their preferred options.
- Additional contexts: wider target deployments for people to use a consensus
  node in more contexts e.g. mobile, wasm, etc.

## Beta Releases

Every few weeks, we release a new Zebra beta [release](https://github.com/ZcashFoundation/zebra/releases).

Zebra's network stack is interoperable with `zcashd`,
and Zebra implements all the features required to reach Zcash network consensus.

The goals of the beta release series are for Zebra to act as a fully validating Zcash node,
for all active consensus rules as of NU5 activation.

Currently, Zebra validates all of the documented Zcash consensus rules, but it may not validate any:
- Undocumented rules derived from Bitcoin
- Undocumented network protocol requirements

## Getting Started

Building `zebrad` requires [Rust](https://www.rust-lang.org/tools/install),
[libclang](https://clang.llvm.org/get_started.html), and a C++ compiler.

### Build and Run Instructions

`zebrad` is still under development, so there is no supported packaging or
install mechanism. To run `zebrad`, follow the instructions to compile `zebrad`
for your platform:

1. Install [`cargo` and `rustc`](https://www.rust-lang.org/tools/install).
2. Install Zebra's build dependencies:
     - **libclang:** the `libclang`, `libclang-dev`, `llvm`, or `llvm-dev` packages, depending on your package manager
     - **clang** or another C++ compiler: `g++`, `Xcode`, or `MSVC`
3. Run `cargo install --locked --git https://github.com/ZcashFoundation/zebra --tag v1.0.0-beta.5 zebrad`
4. Run `zebrad start` (see [Running Zebra](user/run.md) for more information)

If you're interested in testing out `zebrad` please feel free, but keep in mind
that there is a lot of key functionality still missing.

For more detailed instructions, refer to the [documentation](https://zebra.zfnd.org/user/install.html).

### System Requirements

The recommended requirements for compiling and running `zebrad` are:
- 4+ CPU cores
- 16+ GB RAM
- 50GB+ available disk space for building binaries and storing finalized state
- 100+ Mbps network connections

We continuously test that our builds and tests pass on:

The *latest* [GitHub Runners](https://docs.github.com/en/actions/using-github-hosted-runners/about-github-hosted-runners#supported-runners-and-hardware-resources) for:
- macOS
- Ubuntu

Docker:
- Debian Bullseye

Zebra's tests can take over an hour, depending on your machine.
We're working on making them faster.

`zebrad` might build and run fine on smaller and slower systems - we haven't
tested its exact limits yet.

For more detailed requirements, refer to the [documentation](https://zebra.zfnd.org/user/requirements.html).

#### Memory Troubleshooting

If Zebra's build runs out of RAM, try setting:
`export CARGO_BUILD_JOBS=2`

If Zebra's tests timeout or run out of RAM, try running:
`cargo test -- --test-threads=2`

(cargo uses all the processor cores on your machine by default.)

#### macOS Test Troubleshooting

Some of Zebra's tests deliberately cause errors that make Zebra panic.
macOS records these panics as crash reports.

If you are seeing "Crash Reporter" dialogs during Zebra tests,
you can disable them using this Terminal.app command:
```sh
defaults write com.apple.CrashReporter DialogType none
```

### Network Ports and Data Usage

By default, Zebra uses the following inbound TCP listener ports:
- 8233 on Mainnet
- 18233 on Testnet

Zebra needs some peers which have a round-trip latency of 2 seconds or less.
If this is a problem for you, please
[open a ticket.](https://github.com/ZcashFoundation/zebra/issues/new/choose)

`zebrad`'s typical mainnet network usage is:
- Initial sync: 30 GB download
- Ongoing updates: 10-100 MB upload and download per day, depending on peer requests

Zebra also performs an initial sync every time its internal database version changes.

For more detailed information, refer to the [documentation](https://zebra.zfnd.org/user/run.html).

#### Network Troubleshooting

Some of Zebra's tests download Zcash blocks, so they might be unreliable depending on your network connection.
You can set `ZEBRA_SKIP_NETWORK_TESTS=1` to skip the network tests.

Zebra may be unreliable on Testnet, and under less-than-perfect network conditions.
See our [roadmap](#future-work) for details.

### Disk Usage

Zebra uses up to 40 GB of space for cached mainnet data,
and 10 GB of space for cached testnet data.

RocksDB cleans up outdated data periodically,
and when the database is closed and re-opened.

#### Disk Troubleshooting

Zebra's state commits changes using RocksDB database transactions.

If you forcibly terminate Zebra, or it panics,
any incomplete changes will be rolled back the next time it starts.

So Zebra's state should always be valid, unless your OS or disk hardware is corrupting data.

## Known Issues

There are a few bugs in Zebra that we're still working on fixing:
- [In rare cases, Zebra panics on shutdown #1678](https://github.com/ZcashFoundation/zebra/issues/1678)
  - See [#2209](https://github.com/ZcashFoundation/zebra/issues/2209) for an example.
  - These panics can be ignored, unless they happen frequently.
- [Interrupt handler does not work when a blocking task is running #1351](https://github.com/ZcashFoundation/zebra/issues/1351)
  - Zebra should eventually exit once the task finishes. Or you can forcibly terminate the process.
- [No Windows support #3801](https://github.com/ZcashFoundation/zebra/issues/3801)
  - We used to test with Windows Server 2019, but not anymore; see issue for details

## Future Work

In 2022, we intend to start adding RPC support and start adding wallet integrations.
This phased approach allows us to test Zebra's independent implementation of the
consensus rules, before asking users to entrust it with their funds.

Features:
- RPC functionality
- Wallet functionality

Performance and Reliability:
- Reliable syncing on Testnet
- Reliable syncing under poor network conditions
- Additional batch verification
- Performance tuning

Currently, the following features are out of scope:
- Mining support
- Optional Zcash network protocol messages
- Consensus rules removed before Canopy activation (Zebra checkpoints on Canopy activation)

## Documentation

The [Zebra website](https://zebra.zfnd.org/) contains user documentation, such
as how to run or configure Zebra, set up metrics integrations, etc., as well as
developer documentation, such as design documents.  We also render [API
documentation](https://doc.zebra.zfnd.org) for the external API of our crates,
as well as [internal documentation](https://doc-internal.zebra.zfnd.org) for
private APIs.

## Security

Zebra has a [responsible disclosure policy](https://github.com/ZcashFoundation/zebra/blob/main/SECURITY.md), which we encourage security researchers to follow.

## License

Zebra is distributed under the terms of both the MIT license
and the Apache License (Version 2.0).

See [LICENSE-APACHE](LICENSE-APACHE) and [LICENSE-MIT](LICENSE-MIT).
