Claude Local Files

Claude Local Files

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](https://github.com/runekaagaard/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/ dire