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Before you can run the Document Download Frontend, you need to install several dependencies and tools.

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Prerequisites

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Node.js and nvm

The project requires Node.js version 24 (as specified in .nvmrc).
1

Install Node.js via Homebrew (if not already installed)

If you don’t have Node.js on your system:
brew install node
2

Install nvm

nvm is a tool for managing different versions of Node.js. Follow the guidance on nvm’s GitHub repository to install it.Once installed, you can switch between Node.js versions easily.
3

Switch to the correct Node.js version

Run the following command in the project directory:
nvm use
If you don’t have Node.js v24 installed, nvm will tell you how to install it:
nvm install 24

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Python and uv

The project uses uv for Python dependency management.
1

Install uv

Install uv using the official installation script:
curl -LsSf https://astral.sh/uv/install.sh | sh
Alternatively, you can use other installation methods described in the uv documentation.

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Pre-commit

The project uses pre-commit to ensure that committed code meets basic standards for formatting.
1

Install pre-commit system-wide

brew install pre-commit
2

Install pre-commit hooks in the repository

Navigate to the project directory and run:
pre-commit install --install-hooks
This will set up the following hooks:
  • Trailing whitespace removal
  • End-of-file fixer
  • YAML validation
  • Debug statement detection
  • Ruff linting and formatting

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Python Dependencies

The project uses several Python packages including:
  • Flask (3.1.3) - Web framework
  • Flask-WTF (1.2.1) - Form handling
  • govuk-frontend-jinja (4.0.0) - GOV.UK Design System templates
  • notifications-utils - Shared utilities from GOV.UK Notify
  • notifications-python-client (10.0.0) - Notify API client
  • Gunicorn (25.1.0) - WSGI HTTP server
  • Sentry SDK (1.45.1) - Error tracking
  • Whitenoise (6.2.0) - Static asset management

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Node.js Dependencies

The project uses:
  • govuk-frontend (6.0.0) - GOV.UK Design System assets
  • Rollup - JavaScript bundler
  • Sass - CSS preprocessor
  • ESLint - JavaScript linting
  • Stylelint - SCSS linting

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Verification

After installation, verify that all tools are available: 
# Check Node.js version
node --version  # Should show v24.x.x

# Check npm version
npm --version

# Check uv version
uv --version

# Check pre-commit installation
pre-commit --version
Once all prerequisites are installed, proceed to the Development Setup guide to bootstrap the project.

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