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CORS Configuration

When your React app runs at http://localhost:5173 (Vite) or http://localhost:3000 (CRA/Next.js), browsers block requests to http://localhost:11434 due to cross-origin restrictions (CORS).

Tell Ollama to allow cross-origin requests by setting the OLLAMA_ORIGINS environment variable.

macOS​

# Temporary (current session)
OLLAMA_ORIGINS="*" ollama serve

# Permanent
launchctl setenv OLLAMA_ORIGINS "*"
# Then restart Ollama

Linux (systemd)​

sudo systemctl edit ollama

Add under [Service]:

[Service]
Environment="OLLAMA_ORIGINS=*"

Then restart:

sudo systemctl restart ollama

Windows​

# Set environment variable
[System.Environment]::SetEnvironmentVariable("OLLAMA_ORIGINS", "*", "User")
# Restart Ollama

Docker​

docker run -d \
  -e OLLAMA_ORIGINS="*" \
  -p 11434:11434 \
  ollama/ollama

Option 2: Vite Proxy (Development only)​

If you're using Vite, add a proxy to vite.config.ts:

vite.config.ts
import { defineConfig } from "vite";
import react from "@vitejs/plugin-react";

export default defineConfig({
  plugins: [react()],
  server: {
    proxy: {
      "/ollama": {
        target: "http://localhost:11434",
        changeOrigin: true,
        rewrite: (path) => path.replace(/^\/ollama/, ""),
      },
    },
  },
});

Then use /ollama as the endpoint:

const { messages, send } = useOllama("gemma3:1b", {
  endpoint: "/ollama",
});

Option 3: Next.js Rewrites​

next.config.js
module.exports = {
  async rewrites() {
    return [
      {
        source: "/ollama/:path*",
        destination: "http://localhost:11434/:path*",
      },
    ];
  },
};

LM Studio​

LM Studio enables CORS by default. No configuration needed.

llama.cpp​

Start the server with CORS enabled:

./llama-server -m model.gguf --host 0.0.0.0 --port 8080 --cors "*"

Verifying CORS​

Check if CORS is configured correctly:

curl -I -X OPTIONS http://localhost:11434/api/chat \
  -H "Origin: http://localhost:5173" \
  -H "Access-Control-Request-Method: POST"

Look for Access-Control-Allow-Origin in the response headers.