Eosio CDT is a free, open-source toolkit for developers who write smart contracts for the EOSIO blockchain. It bundles a WebAssembly toolchain and EOSIO-specific tooling so that contract code written in C or C++ can be compiled into the format the platform runs. Its focus is narrow: it is a build tool for contract authors, not a wallet, miner or trading program.
Before you start, note the project's status. The most recent code update was on July 12, 2021, and the project has had no code updates since then. It may not keep pace with newer compiler releases or platform changes, so treat it as a reference for existing work and read the safety notes below before installing anything.
What Is Eosio CDT and Who Is It For?
Developers who want to write logic for the EOSIO blockchain need a way to turn their source code into WebAssembly, the bytecode format that EOSIO contracts run in. Eosio CDT, short for Contract Development Toolkit, handles that conversion. It is aimed at contract authors who already know C++ and want a dedicated build chain rather than assembling generic compiler tools by hand.
Typical users are blockchain engineers building applications such as token systems, voting logic or game rules on EOSIO. A team might run the toolkit in a continuous integration job to compile contracts each time the code changes. Students and hobbyists exploring EOSIO can use it to learn how contract code maps to the chain's runtime.
Because it is a development aid, the toolkit does not hold keys, sign transactions or manage funds on its own. Its output still has to be tested and deployed through the platform's standard tooling.
How Do WebAssembly Contracts Get Built?
WebAssembly is a compact binary format designed to run code safely and quickly across different environments. Smart contract platforms use it because the runtime can check a module before executing it and limit what the code can touch. Eosio CDT sits between your C++ source and that binary.
The general flow looks like this: you write a contract class in C++, the toolkit compiles it through a Clang-based pipeline, and the output is a WebAssembly module plus any metadata the platform needs. Clang 9 is the compiler frontend the toolkit is built around, which brings LLVM's analysis and optimization passes to the job.
Developers should know one limitation. The WebAssembly target is still considered experimental in this toolchain, and some optimizations are incomplete or unavailable. In practice, compiled modules may be less compact than you expect, so check the size and resource use of your output before deployment.
Key Terms Every EOSIO Contract Developer Meets
Several terms come up repeatedly when working with this toolkit. A toolchain is a set of tools that run in sequence, such as a compiler, a linker and utilities that package the output. A WASM target is the instruction set and format a compiler aims for when it produces WebAssembly. Optimizations are transformations that make code smaller or faster without changing its behavior.
Contract development also involves a split between the build environment and the chain. The toolkit produces artifacts, while the blockchain stores and executes them. Testing usually happens on a local or test network before anything reaches production, since deployed code is difficult to change.
If you are coming from Ethereum, the mental model shifts. EOSIO contracts are written in C or C++ rather than Solidity, and the account and permission model differs. Reading the platform's documentation alongside the toolkit's examples saves time.
Key features
WebAssembly toolchain
EOSIO-specific optimizations
Clang 9 and LLVM foundation
Free, MIT-licensed source code
How to install Eosio CDT on Windows
- 1
Confirm your operating system
The project lists macOS and Linux as its platforms. Windows builds may appear on the releases page, but this is not clearly documented, so check there before planning your setup. If no Windows build is listed, a Linux environment is the practical route for building contracts.
- 2
Download from the official source
Get the files only from the official website or the project's GitHub Releases page at github.com/EOSIO/eosio.cdt. Choose the release that matches your system. The most recent tag in the project's records is eosio-cdt-2.1-staging-c-pre-2.1, which is a staging build, so read the release notes before relying on it.
- 3
Verify the file
Compare the SHA-256 checksum of the downloaded file with the value published alongside the release. If no checksum or signature is published for the file you downloaded, treat that as a reason to stop and look for a verified source instead of installing it.
-
Install and check the setup
Follow the installer or extraction steps in the release notes, then open a terminal and confirm the toolkit's command runs before you start a project. Make sure the machine has at least two CPU cores, because a known issue affects systems with fewer.
System requirements
- A minimum of two CPU cores, due to a known issue in the toolkit
- Documented platforms: macOS and Linux
How to use Eosio CDT
Once the toolkit is installed, a typical session follows a predictable pattern. The steps below assume you have a contract written in C++ and a terminal open in its project folder.
- Create a project folder and place your contract source file inside it.
- Run the toolkit's compiler on the source file, passing an output name for the WebAssembly module.
- Check the output directory for the generated .wasm file and any accompanying ABI or metadata files.
- Inspect the module's size and review every compiler warning, since some optimizations are incomplete.
- Deploy only to a test network first, and move to production only after the contract behaves as expected.
Keep a copy of each build's output alongside the source it came from. When something breaks after an update to your environment, that record makes it much easier to find what changed.
Pros & cons
- Free and open source under the MIT license
- Compiles C and C++ contracts to WebAssembly for EOSIO
- Built on Clang 9 and LLVM, giving access to mature optimizations
- Usable as a general WebAssembly toolchain
- Source code is public and can be reviewed on GitHub
- No code updates since July 2021
- Windows support is not clearly documented
- The WebAssembly target is still experimental
- Some optimizations are incomplete or unavailable
- Requires at least two CPU cores due to a known issue
- Narrow scope: useful only for EOSIO contract developers
Is Eosio CDT safe?
Eosio CDT is a development tool, not a wallet or miner, but the code it produces will run on a live blockchain, so caution matters. The project has had no code updates since July 2021, which means known bugs or compatibility gaps may remain unfixed. Download only from the official website or the GitHub Releases page, then verify the SHA-256 checksum or signature against the value the project publishes before running any installer. Avoid copies from third-party sites, mirrors and forum links. Review the source you compile, test every contract on a test network, and check the latest version on the official website. Keep private keys and seed phrases out of build scripts and never type them into a website you reached from a search result.
- Official source only. Download from github.com/EOSIO/eosio.cdt. Ignore ads and lookalike domains.
- Check the SHA-256. Compare the installer hash with the value the developer publishes before running it.
- Never share your seed phrase. No developer, support agent or website — including CryptApps — will ever ask for it.
Alternatives
Eosio CDT targets one platform: EOSIO. Remix Desktop, Foundry and the Solidity compiler serve the Ethereum ecosystem and use Solidity rather than C++. Anchor is a framework for Solana programs, so its language and runtime are different again. Tenderly CLI and Postman focus on debugging and RPC testing rather than building contracts, so they complement a toolkit like this instead of replacing it.
Choose Eosio CDT when your project targets EOSIO and you accept the maintenance risk that comes with an unmaintained codebase. For Ethereum work, look at Foundry or Remix Desktop. For Solana, Anchor is the matching framework.
Specifications
- Price
- Free
- Type
- Open source
- License
- MIT
- Latest version
- eosio-cdt-2.1-staging-c-pre-2.1
- Last update
- 12 Jul 2021
- Windows support
- Likely (builds for Windows; check releases)
- Source code
- github.com/EOSIO/eosio.cdt
Frequently asked questions
Yes. Eosio CDT is free and released under the MIT license, which allows you to use, copy and modify the code. The source is hosted on GitHub. Free use does not mean free support, since the project has had no code updates since July 2021, so you may need to solve compatibility problems yourself.
Windows support is unclear. The project documents macOS and Linux as its platforms, and Windows builds may or may not be offered. Check the GitHub Releases page for a Windows file. If none is listed, use a Linux environment on your machine or in a separate virtual machine for building contracts.
No. The project has had no code updates since July 12, 2021, so it should be treated as unmaintained. You can still read the source and use the toolkit, but expect to handle platform changes and bugs yourself, and review the project page before starting any new work.
It can be, if you get it from the official source and verify it. Use only the official website or the GitHub Releases page, and check the SHA-256 value before installing. The open license lets you review the code, which is a benefit, but the lack of recent updates means older issues may still be present.
You need at least two CPU cores, because the project notes a known issue that requires this minimum. Beyond that, any modern laptop that runs your editor and terminal comfortably is a sensible starting point for small contracts.
You write contracts in C or C++. Eosio CDT compiles that source into WebAssembly, the format the EOSIO platform executes. Solidity is not used here, so Ethereum tutorials will not transfer directly, though general programming habits and security thinking do carry over.
No. Eosio CDT is built for EOSIO contracts. For Ethereum, Solidity-focused tools such as the Solidity compiler, Foundry or Remix Desktop are the relevant options. Use this toolkit only if your project runs on EOSIO.
Verdict
Eosio CDT suits developers who already work on EOSIO and want a dedicated toolkit for compiling C++ contracts to WebAssembly. It is free, open source and built on a known compiler stack. However, the lack of code updates since July 2021, the experimental WebAssembly target, incomplete optimizations and unclear Windows support make it better suited to maintaining existing projects or learning the platform than to starting large new production work. Test everything on a test network first.