Choosing your development approach

VIKTOR offers two ways to build apps: the App Builder and local development. Both produce the same kind of VIKTOR app — the difference is in how you write and manage the code.

• App Builder — a browser-based environment where an AI assistant helps you build apps without any local setup. Great for getting started quickly.
• Local development — write your app code in your preferred IDE (such as VS Code or PyCharm) on your own machine, using viktor-cli to connect to VIKTOR. Better suited for larger or more complex apps.

note

The App Builder is under active development and updated regularly. The information on this page reflects the current version and will be updated as new features ship. For the most up-to-date list of App Builder limitations, see the Limitations section of the App Builder documentation.

Quick comparison

	App Builder	Local development
Setup required	None — works entirely in the browser	Python, an IDE, and viktor-cli installed on your machine
Getting started	Fast — go from idea to app in minutes	Slower — requires initial setup
Code structure	Single app.py file	Multiple files
Code size	150 KB maximum	No practical limit
Available packages	Fixed set of pre-installed packages	Any Python package
OAuth 2.0 integrations	Supported	Supported
Desktop software integrations	Limited support via workers	Supported via workers
Deployment	Automatic on publish	Manual publish step
Version control	Built-in revision history	Git / any version control system
Testing	Not supported	Write and run automated tests
AI coding assistants	Built-in, VIKTOR-aware AI	Use your own — GitHub Copilot, Claude Code, Cursor, etc.
AI assistant file context	1 file per conversation (documents: 4.5 MB, images: 3.75 MB)	Limited by your AI coding assistant

App Builder

When to choose the App Builder

• You want to get from idea to working app as fast as possible
• You have limited coding experience or are new to Python
• You don't want to install or configure anything locally
• Your app is self-contained and doesn't require complex code organisation

Pros

• No local setup required — works entirely in the browser; no installation needed
• Fast prototyping — go from idea to working app in minutes
• Built-in AI assistant — understands VIKTOR-specific patterns and helps you write code
• Instant deployment — apps are easy to publish with a click of a button
• No environment management — Python version, packages, and dependencies are all handled for you

Cons

• Single file — all code must live in one app.py file
• Code size limit — app.py has a maximum file size of 150 KB
• Fixed package set — only pre-installed packages are available; you cannot add your own
• Limited desktop software integrations — connecting to local desktop software via workers is technically possible, but the App Builder is not optimized for this use case
• Single context file upload — only one file (documents: 4.5 MB, images: 3.75 MB) can be uploaded per conversation to the AI assistant

Local development (IDE + viktor-cli)

When to choose local development

• Your app is large or requires multiple code files
• You need a Python package that is not available in the App Builder
• You want to integrate VIKTOR with local desktop software
• You want to use Git for version control and work in a team with branches and pull requests
• You need automated testing or automated deployment
• You are comfortable with Python, or are using an AI coding assistant to help you get started

Pros

• Full code flexibility — structure your code across multiple files
• Any Python package — no restrictions on which libraries you can use
• Suitable for complex apps — no limits on code size or structure
• Desktop software integrations — connect VIKTOR to local desktop software such as engineering tools
• Git integration — use branches, pull requests, and full version control history
• Automated testing — write and run automated tests
• Automated deployment — set up pipelines to automatically test and publish your app
• AI coding assistants — tools like GitHub Copilot, Claude Code, and Cursor can understand your entire project; use https://docs.viktor.ai/llms-full.txt as context to make them VIKTOR-aware

Cons

• Setup required — you need to install Python, an IDE (such as VS Code or PyCharm), and viktor-cli before you can start building apps
• Steeper learning curve — requires familiarity with Python and working in a terminal
• Slower to get started — more time from idea to running app compared to the App Builder
• VIKTOR SDK knowledge needed — you need to understand how VIKTOR's SDK works to be productive, although AI coding assistants can help bridge this gap

Migrating from App Builder to local development

If you started with the App Builder and have outgrown its limits, you can continue developing locally:

1. In the App Builder, switch to Code mode and copy the contents of app.py.
2. Follow the installation instructions to set up viktor-cli.
3. Create a new local app and paste your code into app.py.
4. From here you can split the code across multiple files, add packages, and connect integrations.