The developer toolkit (AB-400 free lesson)

AB-400: Power Platform Developer replaces PL-400. You can register for PL-400 until 16 October 2026 and sit it until 30 October 2026. AB-400 is available from 16 October 2026. The passing score is 700, and associate certifications renew yearly with a free online assessment.

A Power Platform developer extends what makers build. You write plug-ins in C#, client scripts and PCF components in TypeScript, code apps, Azure Functions, custom connectors and code-first agents.

VS Code with the Power Platform Tools extension is your main editor. The extension also gives you the pac CLI.
The .NET SDK builds plug-ins and runs pac as a .NET tool. Node.js builds PCF components and code apps.
pac auth create connects pac to an environment. The Plug-in Registration Tool registers plug-ins, steps, images and service endpoints.

In plain words

A maker builds with the designers in the browser. A developer goes further. You write code that the designers cannot produce: C# plug-ins that run inside Dataverse, TypeScript controls, client scripts, code apps, Azure Functions and custom connectors.

Think of a carpenter. The maker uses ready-made flat-pack furniture. The developer has a workshop with power tools. This lesson sets up that workshop, so every later lesson just works.

It also explains the exam itself. AB-400: Power Platform Developer is the new developer exam. It replaces PL-400, and it adds newer topics such as code apps, MCP servers, Microsoft Foundry agents and managed identity for plug-ins.

Why it matters

Most failed developer projects do not fail because of hard code. They fail because of a broken setup: the wrong environment, an expired sign-in, a missing SDK or a tool that cannot see the solution. The exam also tests the tools directly. You must know which command or tool does which job.

The dates matter if you are planning when to sit the exam.

Event	Date
Last day to register for PL-400	16 October 2026
Last day to take PL-400 if registered in time	30 October 2026
AB-400 available	From 16 October 2026

The passing score is 700. Like other associate certifications, it renews every year with a free online assessment on Microsoft Learn.

What you should already know. Microsoft aims AB-400 at developers who work with JavaScript, JSON, TypeScript, Power Fx, C#, Python, HTML, YAML, REST APIs, Azure, Microsoft Foundry and Copilot Studio. You do not need to be an expert in all of them. You should be comfortable reading C# and TypeScript, calling a REST API and editing a YAML file. You should also know the PL-900 basics: environments, Dataverse tables, solutions, canvas and model-driven apps, flows and agents.

How it works

Your toolkit has six parts. Each one has a clear job.

Tool	What it does	Used for
Visual Studio Code	Code editor with a built-in terminal	Everything: PCF, client scripts, code apps, YAML
Power Platform Tools extension	Installs pac CLI in VS Code and adds a panel for auth profiles and environments	Switching environments, running pac
pac CLI	Command-line tool for Power Platform	Auth, solutions, PCF, plug-in projects, code apps
.NET SDK	Compiler and build tools for C#	Plug-ins, custom API code, Azure Functions
Node.js and npm	JavaScript runtime and package manager	PCF components, code apps, TypeScript builds
Plug-in Registration Tool	Windows desktop tool that talks to Dataverse	Registering assemblies, steps, images, service endpoints

Installing pac CLI. There are two common ways. The Power Platform Tools extension installs pac for use inside VS Code. You can also install it as a .NET global tool, which works on Windows, macOS and Linux. The launchers for Windows desktop tools, such as the Plug-in Registration Tool, only work with the Windows (.NET Framework) build of pac.

dotnet tool install --global Microsoft.PowerApps.CLI.Tool
pac                      # shows the help and version

Authentication. pac never guesses an environment. You create an auth profile, which is a saved sign-in linked to one environment URL. You can keep many profiles and switch between them.

pac auth create --environment https://chd-dev.crm.dynamics.com
pac auth list            # shows profiles; * marks the active one
pac auth select --index 2
pac org who              # confirms environment and user

For automation you can sign in with a service principal (an app registration in Microsoft Entra ID) instead of a person. You will use this later for CI/CD.

What pac can do. The commands you will use most in this course:

pac solution export, import, unpack, pack and clone move solutions and put them in source control.
pac pcf init and pac pcf push create and deploy PCF components.
pac plugin init creates a plug-in class library project.
pac tool prt launches the Plug-in Registration Tool on Windows.

The .NET SDK and Node.js. Plug-ins are C# class libraries that run in the Dataverse sandbox, so you need the .NET SDK to build them. PCF components and code apps are built with npm scripts, so you need Node.js. Use the LTS release of Node.js.

The Plug-in Registration Tool. Building a plug-in only makes a DLL file. Dataverse does not run it until you register it. The tool uploads the assembly, then adds a step: which message (Create, Update), which table, which pipeline stage, and whether it runs synchronously. It also registers images (snapshots of the row) and service endpoints such as webhooks and Azure Service Bus.

Remember: pac works against the active auth profile. Many “my solution is missing” problems are just the wrong profile selected.

Example: Campus Help Desk

You join the Help Desk team as the developer. Your first day plan:

Install VS Code, the Power Platform Tools extension, the .NET SDK and Node.js LTS.
Run pac auth create --environment https://chd-dev.crm.dynamics.com. Then do the same for the test environment. You now have two profiles.
Run pac auth select to pick dev, then pac solution list. You see Campus Help Desk with the chd publisher prefix.

Export and unpack it into a Git folder so the team can review changes as files:

pac solution export --name CampusHelpDesk --path ./out/chd.zip
pac solution unpack --zipfile ./out/chd.zip --folder ./src/CampusHelpDesk

Create the plug-in project for the priority rule you will write in D.9: pac plugin init in a new folder, then dotnet build.
Launch pac tool prt, connect to dev, and look at the registered assemblies. Nothing is there yet. That is where your priority plug-in will go.

Your workshop is ready. The same setup serves the PCF star-rating control, the custom API chd_EscalateTicket and the staff dashboard code app.

Common mistakes

Running pac against the wrong environment. Always check pac org who before an import.
Thinking a built DLL is live. A plug-in does nothing until it is registered with a step.
Skipping Node.js and then wondering why npm run build fails in a PCF project.
Expecting the Plug-in Registration Tool on macOS. It is a Windows desktop tool. Plan a Windows machine or VM for registration work.
Mixing up the exams. After 30 October 2026 you cannot take PL-400. Study for AB-400, which adds code apps, MCP and Foundry topics.

How the exam asks about it

“Connect”, “sign in”, “target a different environment” with pac → pac auth create or pac auth select.
“Register a step”, “add a pre-image”, “register a webhook” → Plug-in Registration Tool.
“Put the solution in source control as files” → export, then pac solution unpack; the reverse is pack.
“Which prerequisite is missing” scenarios → .NET SDK for plug-ins, Node.js for PCF and code apps.

The developer toolkit

Watch the lesson

At a glance

In plain words

Why it matters

How it works

Example: Campus Help Desk

Common mistakes

How the exam asks about it

Key terms