Tact language

Tact is a fresh programming language for TON Blockchain, focused on efficiency and ease of development. It is a good fit for complex smart contracts, quick onboarding and rapid prototyping.

Developed by TON Studio, powered by the community — at the start of 2025, the number of unique code¹ contracts deployed on the mainnet reached almost 28 thousand, of which about 33% were written in Tact. You can view some selected projects here: Tact in production.

Tact has undergone a comprehensive security audit by Trail of Bits, a leading Web3 security firm.

Try it online!

Tact Documentation

Awesome Tact

Features

The most prominent and distinctive features of Tact are:

• Familiar and user-friendly TypeScript-like syntax.
• Strong static type system with built-in Structs, Messages, and maps, among others.
• First-class maps support, with many methods and a convenient foreach statement for traversing.
• Automatic (de)serialization of incoming messages and data structures.
• Automatic routing of internal, external, and bounced messages.
• Automatic handling of message types, including binary, text, and fallback slices.
• No boilerplate functions for sending messages and deploying child contracts.
• Reusable behaviors through traits.
• Support for low-level programming with asm functions.
• Generation of single-file TypeScript wrappers for convenient interactions with compiled contracts, which include:
  • Type definitions for Structs and Messages observable in the compilation report.
  • Corresponding storeStructureName() and loadStructureName() functions for (de)serialization.
  • All global and contract-level constants.
  • Bi-directional records of exit codes: from their names to numbers and vice versa.
  • Opcodes of all Messages.
  • A contract wrapper class with various helper functions for initialization, deployment, and message exchange.
• Rich standard library.
• Extensive documentation.
• Robust tooling.
• ...and there's much more to come!

Security

• Security audit of Tact by the Trail of Bits (2025, PDF)
  • Backup link: PDF Report

Tact in production

Some selected software and applications based on contracts written in Tact, deployed in production, and consumed by end users:

Open source or source available

• Proof of Capital - Proof of Capital is a market-making smart contract that protects interests of all holders.
  • See the security audit report by Nowarp.

Closed source

• Tradoor - Fast and social DEX on TON.
  • See the security audit report by TonBit.
• PixelSwap - First modular and upgradeable DEX on TON.
  • See the security audit report by Trail of Bits.
• GasPump - TON memecoin launchpad and trading platform.

See Tact in production on the Awesome Tact list.

Installation

Compiler

The Tact compiler is distributed as an NPM package bundled with the Tact standard library.

The recommended Node.js version is 22 or higher, while the minimum version is 18.

Use your favorite package manager to install it into a Node.js project:

# yarn is recommended, but not required
yarn add @tact-lang/compiler

# you can also use npm
npm i @tact-lang/compiler@latest

# or pnpm
pnpm add @tact-lang/compiler

# or bun
bun add @tact-lang/compiler

Alternatively, you can install it globally as such:

npm i -g @tact-lang/compiler

It will make the tact compiler available on your PATH, as well as:

• a convenient unboc disassembler of a contract's code compiled into a Bag of Cells .boc format.
• a formatter tact-fmt, which can format or check the formatting of individual Tact files and directories.

Tooling

Extensions and plugins

• VS Code extension - Powerful and feature-rich extension for Visual Studio Code (VSCode) and VSCode-based editors like VSCodium, Cursor, Windsurf, and others.
  • Get it on the Visual Studio Marketplace.
  • Get it on the Open VSX Registry.
  • Or install from the .vsix files in nightly releases.
• Language Server (LSP Server) - Supports Sublime Text, (Neo)Vim, Helix, and other editors with LSP support.
• tact.vim - Vim 8+ plugin.
• tact-sublime - Sublime Text 4 package.
  • Get it on the Package Control.

Security

• Misti - Static smart contract analyzer.
• TON Symbolic Analyzer (TSA) - Static smart contract analysis tool based on symbolic execution.

Utility

• Formatter (tact-fmt) — The official formatter. It ships with the Tact Language Server, VS Code extension, and as a standalone binary with the compiler. You can invoke it by running npx tact-fmt in your Tact projects.
• BoC Disassembler (unboc) — Disassembler for .boc files. Ships as a standalone binary with the compiler. You can invoke it by running npx unboc in your Tact projects.

Getting started

For a quick start, read the "Let's start!" mini-guide in the Tact documentation. It uses the Blueprint development environment for writing, testing, and deploying smart contracts on TON Blockchain.

If you want more manual control, use tact-template. It's a ready-to-use template with the development environment set up, including the Tact compiler with TypeScript + Jest, a local TON emulator, AI-based editor support, and examples of how to run tests.

git clone --depth 1 https://github.com/tact-lang/tact-template

Community

If you can’t find the answer in the docs, or you’ve tried to do some local testing and it still didn’t help — don’t hesitate to reach out to Tact’s flourishing community:

• @tactlang on Telegram - Main community chat and discussion group.
• @tactlang_ru on Telegram (Russian)
• @tact_kitchen on Telegram - Channel with updates from the team.
• @tact_language on X/Twitter
• tact-lang organization on GitHub
• @ton_studio on Telegram
• @thetonstudio on X/Twitter

Contributing

Contributions are welcome! To help develop the compiler, see the contributing guide.

Footnotes

1. The "unique code" means that each contract in the data sample has at least one TVM instruction that differs from the other contracts, excluding many preprocessed wallets with everything inlined — even seqno and a public key for signature verification! ↩