Mattermost Development

TL;DR

What it is: Building custom plugins, integrations, bots, and extensions for the Mattermost open-source messaging platform. Mattermost is used primarily by enterprises and government organizations that need self-hosted, secure team communication. You develop server-side plugins in Go and optional frontend components in React/TypeScript, connect Mattermost to external tools via APIs and webhooks, and build bots that automate workflows inside the platform.

What you'll do:

• Develop Mattermost server plugins in Go and web app extensions in React/TypeScript
• Build webhook-based integrations connecting Mattermost to external services (CI/CD, ticketing, monitoring)
• Create slash commands and interactive bots for workflow automation
• Extend Mattermost functionality using the REST API and plugin API
• Maintain, update, and troubleshoot custom integrations as the platform evolves

Time to learn: 4-8 months if you already know Go or another backend language and practice 10-15 hours weekly. Longer if starting fresh with Go and the Mattermost plugin architecture.

What you need: Computer, Go development environment, Node.js/npm for frontend work, a local or cloud Mattermost instance for testing, and familiarity with Git and open-source development workflows.

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What This Actually Is

Mattermost is an open-source, self-hosted messaging platform built for organizations that need to control where their data lives. It's used heavily in defense, government, financial services, healthcare, and regulated industries where data sovereignty matters. Think of it as Slack or Microsoft Teams, but deployable on your own servers behind your own firewall.

The platform supports a plugin system that lets developers extend its functionality deeply - both on the server side (Go) and in the web/desktop client (React/TypeScript). On top of that, there's a REST API, incoming and outgoing webhooks, bot accounts, and slash commands for lighter integrations.

The opportunity exists because organizations running Mattermost need custom functionality specific to their workflows. They need integrations with internal tools, compliance-related features, automated processes, or connections to monitoring and incident management systems. Most of these organizations have engineering teams, but those teams are focused on their core product, not on building chat platform extensions. That's where freelance Mattermost developers come in.

This is a niche market. The total number of Mattermost deployments is much smaller than Slack's user base. But the clients who need this work tend to be enterprise or government organizations with real budgets, and the specialized skill set required means there's significantly less competition per opportunity.

What You'll Actually Do

Plugin Development

This is the highest-value and most complex work. Mattermost plugins are full programs - a Go backend that hooks into server events and APIs, and an optional React/TypeScript frontend that modifies the web interface. You might build a plugin that integrates with an internal HR system, adds custom message formatting for a compliance requirement, or creates an entirely new UI panel in the sidebar.

Server-side plugins can intercept messages, respond to events (user joins, channel created, message posted), add API endpoints, store data in a key-value store, and run background jobs. Frontend plugins can add buttons, sidebar components, custom post types, and interactive modals.

You'll work with Mattermost's plugin starter template, build and bundle your plugin, and deploy it to test instances. The development cycle involves writing Go code, compiling the plugin, uploading it to Mattermost, and testing within the running application.

Webhook and API Integrations

Not everything requires a full plugin. Many integration needs can be met with webhooks and the REST API. Incoming webhooks let external services post messages to Mattermost channels. Outgoing webhooks trigger actions when specific messages are posted. The REST API provides programmatic access to users, channels, posts, teams, and most platform features.

Common integration work includes connecting CI/CD pipelines so build results appear in a developer channel, linking monitoring tools so alerts land in an operations channel, piping ticketing system updates into relevant team channels, or building custom notification flows from internal applications.

These lighter integrations can be written in any language - Python, JavaScript, Go, whatever the client's environment supports. They're faster to build than plugins and often serve as entry-point projects that lead to more complex work.

Bot Development

Mattermost supports bot accounts that can interact with users through messages and slash commands. Bots handle tasks like querying databases, triggering deployments, running status checks, managing on-call rotations, or collecting standup reports. Slash commands let users trigger bot actions by typing commands directly in the message box.

Bot development involves setting up a bot account, writing a service that listens for events via the Mattermost WebSocket API or responds to webhook triggers, and implementing the business logic that processes requests and sends responses. Interactive messages with buttons and menus make bots more user-friendly.

Migration and Deployment Consulting

Some engagements focus on helping organizations migrate from Slack or Microsoft Teams to Mattermost. This involves data migration (conversation history, channels, users), recreating integrations that existed on the previous platform, and configuring Mattermost to match existing workflows. You may also assist with initial Mattermost deployment and configuration, though this overlaps more with DevOps consulting than pure development.

Skills You Need

Go (Golang). This is non-negotiable for plugin development. Mattermost's server is written in Go, and all server-side plugins must be Go code that implements the plugin API interfaces. You need to be comfortable with Go's type system, interfaces, error handling, concurrency patterns, and package management.

React and TypeScript. If you want to build frontend components - custom UI panels, interactive modals, button actions in the web client - you need React and TypeScript. Not every project requires frontend work, but it significantly expands what you can deliver.

REST API and Webhook Design. Understanding HTTP, JSON, authentication patterns, and webhook architecture is fundamental. Most Mattermost integration work revolves around API calls and event-driven communication between systems.

Understanding of Messaging Platform Architecture. You need to understand how team messaging works at a system level - users, teams, channels, permissions, message threading, notifications, and real-time communication via WebSockets. This context shapes how you design integrations that feel native rather than bolted on.

Open-Source Development Practices. Comfort working with Git, reading other people's code, navigating large codebases, and potentially contributing upstream to Mattermost or its community plugins. Being active in the Mattermost open-source community builds credibility and generates leads.

Getting Started

Set Up Your Development Environment

Install Go and set up a local Mattermost server instance for development. Mattermost provides Docker images that make local setup straightforward. Having your own running instance is essential - you need a playground for building and testing plugins without affecting anyone's production environment.

Install the Mattermost developer toolkit (mattermost-developer-kit), which provides templates and CLI tools for generating plugin scaffolding. Familiarize yourself with the plugin starter template on GitHub.

Build Your First Plugin

Start with a simple plugin that responds to a slash command - something like a /weather command that fetches and posts weather data. This teaches you the plugin lifecycle: initializing the plugin, registering slash commands, handling requests, posting messages back to channels, and building/deploying the compiled plugin.

Progress to more complex plugins: one that intercepts messages and adds metadata, one that creates a sidebar component, one that integrates with an external API. Each project teaches a different part of the plugin API.

Contribute to the Ecosystem

Mattermost's community plugin marketplace is an excellent way to build public credibility. Identify a gap - a missing integration, an improvement to an existing community plugin, or a utility that teams commonly need - and build it. Community plugins are reviewed and code-signed by the Mattermost team before listing, which adds legitimacy to your work.

Contributing bug fixes or features to existing plugins also puts your name in front of the Mattermost community. Organizations evaluating developers often check GitHub contribution history.

Note: Platforms may charge fees or commissions. We don't track specific rates as they change frequently. Check each platform's current pricing before signing up.

Build a Portfolio and Start Outreach

Document your plugins and integrations with clear README files, screenshots, and architecture explanations. Your GitHub profile effectively becomes your portfolio in this space.

List your services on freelance platforms targeting enterprise clients. Position yourself specifically around Mattermost development rather than generic software development. On LinkedIn, connect with CTOs, DevOps managers, and IT leaders at organizations in regulated industries where Mattermost adoption is concentrated.

Income Reality

Mattermost development commands solid rates because it combines niche platform knowledge with Go expertise, which is itself a higher-rate skill than more common languages.

Small integration projects - webhook setups, simple bot commands, connecting a single external service to Mattermost - typically earn $500-$2,000 per project. These can usually be completed in a few days to a week.

Mid-complexity work like custom plugin development with server and frontend components, multi-service integration setups, or bot development with interactive features generally ranges from $3,000-$10,000 per project, spanning two to six weeks.

Large enterprise engagements - platform migrations from Slack or Teams, custom compliance plugins, complex multi-system integration suites, or ongoing development retainers - can run $10,000-$40,000+ per engagement over several months.

Hourly rates for freelance Mattermost developers typically fall between $60-$120/hour depending on experience and client region. The Go specialization pushes rates toward the higher end compared to general web development work.

Retainer arrangements for ongoing plugin maintenance, version compatibility updates, and incremental feature development are common. These typically range from $500-$3,000/month per client.

Your actual earnings depend on how many clients you serve, project complexity, whether you secure recurring maintenance work, and how effectively you position yourself in the enterprise market. Many Mattermost developers also work with other open-source platforms and API development projects, which broadens available work.

Where to Find Work

Upwork and Toptal are the primary freelance platforms where Mattermost-related projects surface. Search for "Mattermost," "Go developer," "chat integration," or "messaging platform development." Toptal's vetting process gives you access to higher-budget enterprise clients willing to pay premium rates.

LinkedIn is particularly effective for this niche because Mattermost's customer base is enterprise-heavy. Post about Mattermost integrations, share plugin development tips, and connect with engineering and IT leadership at organizations in defense, financial services, healthcare, and government sectors.

Mattermost's Partner Directory lists consulting firms and independent developers that provide services around the platform. Getting listed expands your visibility to organizations actively looking for Mattermost expertise.

GitHub and the Mattermost Community. Being visible in the Mattermost open-source community - answering questions in forums, contributing code, publishing plugins to the marketplace - generates inbound leads from organizations that see your expertise firsthand. The community forums and contributor channels are where many organizations start their search for developers.

Direct Outreach to organizations that publicly use or are evaluating Mattermost works well. Government RFP sites, defense contractor job boards, and enterprise IT communities surface organizations with Mattermost needs. A cold email demonstrating relevant plugin or integration work you've already built is far more effective than a generic pitch.

Common Challenges

Niche Market Size

The total addressable market for Mattermost development is significantly smaller than for Slack apps or general web development. You won't find dozens of new Mattermost projects posted weekly on freelance platforms. Building a pipeline requires consistent networking, community involvement, and sometimes combining Mattermost work with adjacent services like general Go development or DevOps consulting.

Plugin API Versioning

Mattermost evolves between major versions, and plugin APIs can change. A plugin built for Mattermost 9.x may need adjustments for 10.x. Maintaining compatibility across versions is part of the work, and clients running older self-hosted versions may need plugins that target specific API versions. This adds maintenance overhead but also creates recurring revenue opportunities.

Long Enterprise Sales Cycles

Enterprise and government organizations don't move fast. A "we need a Mattermost plugin" conversation might take months to become a signed contract, especially in government procurement. You need financial patience and a pipeline of multiple opportunities at different stages to maintain consistent income.

Managing Scope in Integration Projects

Integration work is notorious for scope creep. "Connect our ticketing system to Mattermost" sounds simple, but quickly expands into bidirectional sync, rich message formatting, interactive buttons for ticket actions, user mapping between systems, and error handling for dozens of edge cases. Define deliverables precisely and use phased proposals.

Debugging Across Systems

When a Mattermost plugin interacts with external APIs and services, debugging issues that span multiple systems is significantly harder than debugging isolated code. You'll need strong logging practices, familiarity with network debugging tools, and the ability to read Mattermost server logs alongside external service logs to trace problems across system boundaries.

Tips That Actually Help

Master Go deeply, not just for Mattermost. Your Go skills are what command premium rates. Investing in Go proficiency pays dividends across Mattermost work and other backend development. The stronger your Go fundamentals, the faster you'll build reliable plugins.

Study existing plugins. The Mattermost plugin ecosystem on GitHub contains dozens of open-source plugins. Read the code for popular ones like the Jira, GitHub, and Zoom plugins. These are maintained by the Mattermost team and demonstrate best practices for plugin architecture, error handling, and API usage.

Automate your development workflow. Set up a local development environment where you can compile, deploy, and test plugins quickly. The faster your feedback loop between code change and running test, the more productive you are. Mattermost's plugin development documentation includes tips for streamlining this process.

Focus on regulated industries. Defense, government, healthcare, and financial services organizations are where Mattermost adoption is concentrated. Understanding the compliance context - why these organizations self-host, what data handling requirements they face - makes you a more effective consultant, not just a developer.

Publish to the community marketplace. Even if you don't earn directly from open-source plugins, listed marketplace plugins are visible proof of your skills. Potential enterprise clients evaluating Mattermost developers will check the marketplace. Having your name on multiple well-built plugins is powerful social proof.

Offer maintenance alongside builds. Enterprise clients running custom plugins need someone to maintain them as Mattermost updates. Including a maintenance retainer option in every project proposal gives you recurring revenue and keeps you connected to the client for future work.

Is This For You

Mattermost development is a strong fit if you're a backend developer who knows Go (or is motivated to learn it) and prefers working with enterprise clients on focused, technical projects rather than chasing high-volume small gigs. The combination of Go expertise and niche platform knowledge creates a relatively uncrowded space with better-than-average rates.

It works particularly well as a complement to broader Go development or DevOps consulting work. Having Mattermost as a specialization within a broader backend or infrastructure skill set keeps your pipeline healthy even when Mattermost-specific opportunities are sparse.

The enterprise and government client base means professional, structured engagements with clear requirements and real budgets. It also means longer sales cycles, procurement processes, and occasionally bureaucratic communication. If you prefer fast-moving startup environments over structured enterprise work, the client profile may not suit you.

You do need genuine interest in messaging platforms, integration architecture, and how teams use communication tools. Building effective Mattermost extensions requires understanding user workflows, not just writing code that compiles. The best Mattermost developers think about how their plugin fits into a team's daily communication patterns, not just whether it technically works.

Note on specialization: This is a highly niche field that requires very specific knowledge and skills. Success depends heavily on understanding the technical details and nuances of Go plugin development, messaging platform architecture, and the enterprise security landscape that drives Mattermost adoption. Consider this only if you have genuine interest and willingness to learn the specifics.