Claude Local Files

May 23, 2025 ยท View on GitHub

Artifacts in Claude Desktop can only access cdn.jsdelivr.net/pyodide/* due to Content Security Policy restrictions. This app bypasses that restriction and allows Claude Desktop artifact and analysis tools to fetch local files and use them for calculations, UI's, etc.

I use it with mcp-alchemy to have Claude Desktop generate UI reports for database result sets that are way too large for an LLM to read.

How it works

  1. Adds a line in /etc/hosts that points cdn.jsdelivr.net to 127.0.0.1
  2. Uses mkcert to generate a valid local SSL certificate for cdn.jsdelivr.net
  3. Starts a caddy server that proxies all other requests than to a specfic url folder to Fastly
  4. Files in the ./files directory are served at https://cdn.jsdelivr.net/pyodide/claude-local-files/[FILENAME]
  5. Removes the line in /etc/hosts on exit

Installation

Ubuntu/Debian

# Install dependencies
sudo apt update
sudo apt install mkcert caddy

macOS

# Install dependencies
brew install mkcert caddy

Windows

Run in an elevated powershell (as administrator):

# Install dependencies
winget install CaddyServer.Caddy
winget install FiloSottile.mkcert

# Run the script
./claude-local-files.ps1

Usage

  1. Clone and enter the repository:
git clone https://github.com/runekaagaard/claude-local-files.git
cd claude-local-files
  1. Start the server:
./claude-local-files.sh

  1. Add your files to the files/ directory

  2. Ask Claude Desktop to use the content of the file in a code artifact, e.g. https://cdn.jsdelivr.net/pyodide/claude-local-files/test.json

Testing

Test that the local server works:

curl -v https://cdn.jsdelivr.net/pyodide/claude-local-files/test.json

Test that CDN passthrough works:

curl -v https://cdn.jsdelivr.net/npm/jquery/dist/jquery.min.js

Generating URLs

To serve a file:

  1. Place it in the files/ directory
  2. Access it at https://cdn.jsdelivr.net/pyodide/claude-local-files/[FILENAME]

Example:

  • File: files/test.json
  • URL: https://cdn.jsdelivr.net/pyodide/claude-local-files/test.json

Security Notes

  • Only runs locally - the cdn.jsdelivr.net interception is only on your machine
  • Uses proper HTTPS with valid certificates via mkcert
  • Scripts cleans up /etc/hosts modifications on exit
  • Certificates are stored in the git root directory

Development

Pull requests welcome! Areas for improvement:

  • Windows support
  • Better logging options

License

Mozilla Public License 2.0

My Other LLM Projects

  • MCP Alchemy - Connect Claude Desktop to databases for exploring schema and running SQL.
  • MCP Redmine - Let Claude Desktop manage your Redmine projects and issues.
  • MCP Notmuch Sendmail - Email assistant for Claude Desktop using notmuch.
  • Diffpilot - Multi-column git diff viewer with file grouping and tagging.