Python v3.1.0

Installation

Choose a language from the site navigation. The selection applies across the documentation and is preserved as you move between pages.

These instructions target coordinated release 3.1.0 across all ten implementations. Frozen 3.0.0 documentation remains available.

Install the Python package from PyPI:

pip
Poetry
Pipenv
uv

pip install slackblocks

poetry add slackblocks

pipenv install slackblocks

uv add slackblocks

Python 3.x requires Python 3.10 or newer and has no runtime dependencies. See Compatibility for the support matrix and 1.x migration guidance.

Verify the installation:

from slackblocks import Message, SectionBlock

print(Message(channel="#general", blocks=SectionBlock("Hello, world!")).json())

Pin the current major release with slackblocks~=3.0, and uninstall with pip uninstall slackblocks (or the equivalent command for your package manager).

Install the ESM package from npm:

pnpm
npm
Yarn

pnpm add @nicklambourne/slackblocks

npm install @nicklambourne/slackblocks

yarn add @nicklambourne/slackblocks

The package requires Node 20.19 or newer, is ESM-only, and emits no runtime imports beyond your own code.

Verify the installation in hello.mjs:

import { Message, SectionBlock } from "@nicklambourne/slackblocks";

console.log(
  Message()
    .channel("C0123456")
    .blocks(SectionBlock().text("Hello, world!"))
    .build(),
);

Run it with node hello.mjs. Stay on the 3.x release line with @nicklambourne/slackblocks@^3.1.0, and uninstall with pnpm remove @nicklambourne/slackblocks (or your package manager's equivalent).

From an existing Go module, install the v3 Go module directly from GitHub:

go get github.com/nicklambourne/slackblocks/go/v3

Go 1.22 or newer is required. Block builders implement slack.Block directly using the Go 1.22-compatible github.com/slack-go/slack release; go get installs that dependency automatically. See the Go support matrix for tested SDK versions and how to opt into a newer SDK without changing the library’s minimum Go version.

Verify the installation in main.go:

package main

import (
    "fmt"

    slackblocks "github.com/nicklambourne/slackblocks/go/v3"
)

func main() {
    payload, err := slackblocks.NewMessage().
        Channel("C0123456").
        Blocks(slackblocks.NewSectionBlock().Text("Hello, world!")).
        Build()
    if err != nil {
        panic(err)
    }
    fmt.Println(payload)
}

Run it with go run .. The /v3 suffix is part of the module path under Go's semantic import versioning; update within the current major line with go get -u github.com/nicklambourne/slackblocks/go/v3.

Install the Java artifact from Maven Central. Java 17 or newer is required.

Maven
Gradle (Kotlin)
Gradle (Groovy)

<dependency>
  <groupId>io.github.nicklambourne</groupId>
  <artifactId>slackblocks</artifactId>
  <version>3.1.0</version>
</dependency>

implementation("io.github.nicklambourne:slackblocks:3.1.0")

implementation 'io.github.nicklambourne:slackblocks:3.1.0'

The core artifact includes the official Slack Block Kit model interfaces so completed blocks can be passed directly to the Slack Java SDK. Add com.slack.api:slack-api-client separately when your application sends messages; keeping the transport client optional avoids pulling HTTP dependencies into applications that only construct payloads.

Verify the installation:

import io.github.nicklambourne.slackblocks.SlackblocksJson;
import io.github.nicklambourne.slackblocks.block.SectionBlock;

public final class HelloSlackblocks {
  public static void main(String[] args) {
    var block = SectionBlock.builder().markdownText("Hello, world!").build();
    System.out.println(SlackblocksJson.write(block));
  }
}

Import slackblocks types by name

Several slackblocks class names, such as SectionBlock, HeaderBlock, and ButtonElement, also exist in the Slack SDK's com.slack.api.model.block packages. Import slackblocks classes individually, as the examples on this site do. A file that combines import com.slack.api.model.block.*; with a slackblocks wildcard import fails to compile with a "reference to SectionBlock is ambiguous" error.

Pin compatible 3.x updates with Maven's dependency-management facilities or your usual version catalog. slackblocks' Java artifact uses the same release number as every other language package.

Install the NuGet package. .NET 8 or newer is required.

.NET CLI
PackageReference

dotnet add package Slackblocks

<PackageReference Include="Slackblocks" Version="3.1.0" />

The package depends on nothing beyond .NET itself. It builds and validates payloads and leaves delivery to HttpClient or the Slack client library you already use.

Verify the installation:

using Slackblocks.Blocks;

var block = new SectionBlock(text: "Hello, world!");
Console.WriteLine(block.ToJson());

Alias a namespace when combining Slack libraries

Some slackblocks type names, such as SectionBlock and ButtonElement, also exist in .NET Slack client libraries such as SlackNet. A file that imports both namespaces fails to compile with an ambiguous reference error. Import only the namespaces a file needs, or alias one of them:

using Blocks = Slackblocks.Blocks;

var block = new Blocks.SectionBlock(text: "Hello, world!");

The NuGet package version moves in lockstep with every other language package. A floating version such as 3.* accepts compatible 3.x updates.

Install the gem from RubyGems. MRI Ruby 3.3 or newer is required.

gem install slackblocks

Or add it to your Gemfile:

gem "slackblocks", "~> 3.0"

The runtime uses Ruby and the default json gem. It does not install a Slack transport client.

Verify the installation:

require "slackblocks"

message = Slackblocks::MessagePayload.new(
  channel: "C01234567",
  text: "Hello, world!",
  blocks: [Slackblocks::SectionBlock.new(text: "Hello, world!")]
)
puts message.to_json

Uninstall with gem uninstall slackblocks.

Install from crates.io

Rust 1.85 or newer is required. The crate uses edition 2024, Serde and serde_json. Rust support begins with coordinated version 2.6.0.

cargo add slackblocks@3.1.0
cargo add serde_json

The equivalent dependency is slackblocks = "3.1.0". The package includes generated sources; application builds do not require Python or the shared specification directory. Use cargo update within your normal Cargo version policy.

Verify construction and serialization

use slackblocks::*;

fn main() -> Result<(), Box<dyn std::error::Error>> {
    let message = MessagePayload::builder("C01234567")
        .text("Hello from slackblocks!")
        .block(SectionBlock::builder().text("Hello, world!").build()?)
        .build()?;
    println!("{}", serde_json::to_string(&message)?);
    Ok(())
}

Run the example with cargo run. Remove the dependency with cargo remove slackblocks. See Compatibility for the MSRV and Migration for Rust naming and editing conventions. HTTP clients are application dependencies.

Install with Composer

PHP 8.2 or newer is required, on a 64-bit build with the JSON and PCRE extensions. The core has no third-party runtime dependencies. Composer 2 handles PSR-4 autoloading.

PHP support begins with coordinated version 2.7.0. Install the Packagist package:

composer require nicklambourne/slackblocks:^3.0

Stable installs download a PHP-only archive. Composer's --prefer-source option checks out the monorepo and is required for unreleased development branches. Keep vendor/autoload.php in your application's entry point and use declare(strict_types=1) in your calling PHP files. PHP 8.2's named arguments, readonly classes and backed enums are the public API; named parameter spelling is part of compatibility.

Verify construction and serialization

<?php

declare(strict_types=1);

require 'vendor/autoload.php';

use Slackblocks as S;

$message = new S\MessagePayload(
    channel: 'C0123456789',
    text: 'Build #482 passed',
    blocks: [
        new S\HeaderBlock('Build #482 passed'),
        new S\SectionBlock(fields: ["*Branch*\n`main`", "*Tests*\n1,247 passed"]),
        new S\ActionsBlock(elements: [
            new S\ButtonElement(text: 'View build', actionId: 'view', url: 'https://ci.example.com/482'),
        ]),
    ],
);
echo $message->toJson();

Elixir support begins with 2.8.0, published on Hex. Elixir 1.16.3+ (below 2.0), compatible OTP 26.2+, and a 64-bit runtime are required. Jason and Decimal are runtime dependencies; HTTP clients are optional.

Add the package to the dependency list in your application's mix.exs:

{:slackblocks, "~> 3.0"}

Then fetch and compile dependencies:

mix deps.get
mix compile

Existing Jason builds: if Jason was compiled before Decimal was installed, run mix deps.compile jason --force in each build environment (including MIX_ENV=prod), then rebuild your application and releases. Jason chooses its optional Decimal decoder at compile time. Checked slackblocks decoding returns an actionable tagged error until that integration is rebuilt. Fresh dependency builds include Decimal normally.

Verify construction and serialization:

alias Slackblocks.Blocks.Section
section = Section.new!(text: "Hello, *world*!")
Slackblocks.to_map!(section)

Use mix deps.update slackblocks to update within your declared version range. Commit your application's mix.lock. To uninstall, remove the dependency entry and run mix deps.clean slackblocks --unlock. The library starts no processes and needs no supervision-tree entry. For Rebar3 projects, see Erlang integration.

Haskell availability and toolchain

Haskell joins coordinated 3.1.0 on Hackage.

GHC 9.6.7+ within the tested compiler series is required. Development uses Cabal 3.16.1.0; the package declares Cabal syntax 3.0 and GHC2021.

Declare slackblocks >= 3.1 && < 3.2, aeson and base in your application's build-depends. Run cabal update, then cabal build or cabal run from the application. Cabal resolves the package from Hackage; do not use cabal install to add a library into an application's dependency graph.

To develop against a source checkout instead, build an actual distributable:

cd haskell
cabal build lib:slackblocks
cabal sdist --output-directory=dist

In a separate application's cabal.project, list its package and the local archive, replacing the absolute path with your archive location:

packages: . /absolute/path/slackblocks-3.1.0.tar.gz

Keep the same build-depends. Remove the archive from packages to return to registry resolution.

The core depends on Aeson, text, bytestring, containers, scientific and vector. It does not depend on an HTTP client or Slack SDK. Development dependency locks are not imposed on applications. OverloadedStrings makes text literals usable without repetitive Text.pack calls.

{-# LANGUAGE OverloadedStrings #-}

import Data.Aeson (encode)
import qualified Data.Map.Strict as Map
import Slackblocks

example :: Result MessagePayload
example = do
  text <- buildMarkdownText (markdownText "Hello, *Haskell*!")
  section <- buildSectionBlock (sectionBlock {sectionBlockText = Just (markdownTextAsText text)})
  buildMessagePayload
    ( (messagePayload "C0123456789")
        { messagePayloadText = Just "Hello, Haskell!",
          messagePayloadBlocks = Just [sectionBlockAsBlock section]
        }
    )

Handle Left errors; on Right payload, encode with Aeson. The sending guide shows the separately resolved HTTP integration.

Import slackblocks types by name​

Alias a namespace when combining Slack libraries​

Install from crates.io​

Verify construction and serialization​

Install with Composer​

Verify construction and serialization​

Haskell availability and toolchain​

Import slackblocks types by name

Alias a namespace when combining Slack libraries

Install from crates.io

Verify construction and serialization

Install with Composer

Verify construction and serialization

Haskell availability and toolchain