anthropic api connection error

A connection error occurs when your local development machine or production server fails to reach api.anthropic.com at the network level. This prevents your application from even sending its payload to Claude, resulting in an immediate crash of your SDK script before any HTTP response code is returned.

Validate your base URL and endpoint configuration

If you are using a custom reverse proxy or local gateway, double-check your SDK initialisation. Ensure your base URL is spelt correctly and points to the official endpoint. If your app cannot connect, it might be worth verifying if the main platform is accessible using our guide for when the Claude app won't load.

Resolve local DNS and network routing blocks

Your server's DNS resolver may fail to map the Anthropic API domain to its active IP addresses. Try changing your system DNS to a reliable public resolver, such as Google DNS (8.8.8.8) or Cloudflare (1.1.1.1). Run a quick diagnostic traceroute to check where the packet transmission fails.

Update your SDK and verify system SSL certificates

Outdated development environments or expired local SSL certificates will cause handshake failures during HTTPS connections. Ensure you are running the latest version of the Python (pip install --upgrade anthropic) or Node.js (npm install @anthropic-ai/sdk) libraries to prevent compatibility glitches.

Adjust firewall and HTTP proxy settings

If your code runs behind an enterprise firewall, it might block outgoing connections on port 443. Whitelist api.anthropic.com in your firewall settings, or configure the SDK to route traffic through an approved outbound HTTP proxy by setting the appropriate environment variables.

Implement retry logic with exponential backoff

Temporary internet routing hiccups can cause sporadic connection drops. Always wrap your API calls in try-except blocks and deploy an exponential backoff retry mechanism. This prevents a brief network flicker from crashing your entire application. If the server itself is down, check our guide on the Anthropic API 529 overloaded error.