Fix Claude 'Error Sending Message' Connection Error

The "Error sending message. Please try again" error is a common message shown in the Claude.ai web interface. It typically appears as a red or orange banner at the bottom of the chat window. This error indicates that the web client's connection to Anthropic's backend servers was disrupted mid-transaction, preventing the payload from being processed or preventing the response stream from establishing.

Because this is a general-purpose connection failure, the root cause can range from localized browser issues to full-scale platform outages. Follow these step-by-step instructions to isolate and fix the connection.

1. Check for Active Claude Outages

If Anthropic's servers are experiencing an outage or degraded performance, no amount of troubleshooting on your computer will fix the issue.

1. Go to status.anthropic.com in your browser.
2. Look at the status of the Claude.ai web app system.
3. If there is an active incident, outage, or maintenance window, wait until the status page indicates a full resolution before trying to send your message again.

2. Hard Refresh Your Browser

A standard browser refresh often reuses cached assets that may contain expired authentication tokens or broken WebSocket references. A hard refresh forces the browser to pull down fresh resources.

• On Windows/Linux (Chrome, Edge, Firefox): Press Ctrl + F5 or hold Ctrl and click the reload icon.
• On macOS (Chrome, Firefox): Press Cmd + Shift + R.
• On macOS (Safari): Hold Option and click the reload icon, or press Cmd + Option + E to empty the cache, then reload.

After reloading, attempt to type your prompt in a new chat window rather than continuing the broken conversation stream.

3. Disable Extensions Blocking WebSockets or SSE

Claude.ai relies on Server-Sent Events (SSE) and WebSockets to stream real-time text responses to your browser. Many privacy extensions, ad blockers, and custom firewalls block these background protocols by default.

1. Open an Incognito / Private Browsing window. This opens the browser without your active extensions loaded.
2. Navigate to claude.ai, log in, and try sending the message.
3. If it works, the culprit is one of your browser extensions. Temporarily disable security, privacy, script-blocking, or ad-blocking extensions one by one to isolate which one is preventing the stream.
4. Whitelist *.claude.ai and *.anthropic.com in the settings of the offending extension.

4. Clear Local Storage and Session Cookies

Corrupted cookies or expired local sessions can cause the API handshakes to fail silently, resulting in an "Error sending message" banner.

1. Click the lock/tune icon to the left of the URL bar in your browser while on claude.ai.
2. Select Site settings or Cookies and site data.
3. Click Clear data or delete all stored cookies for the domain.
4. Close your browser completely, reopen it, navigate back to the site, and sign in again.

5. Switch Off Active VPNs and Proxies

Anthropic uses cloud security providers (like Cloudflare) to protect its web application from automated attacks. Many public VPN nodes and proxies are flagged or blocked by these security layers, leading to dropped WebSocket connections.

1. Disconnect from your VPN or proxy client.
2. Open your command terminal (Command Prompt on Windows or Terminal on macOS) and run ping claude.ai to ensure stable latency.
3. Attempt to use Claude.ai using your raw residential or commercial ISP connection.

When to Escalate

If the status page shows all systems operational, but you consistently receive the "Error sending message" across multiple browsers, networks (e.g., trying both Wi-Fi and mobile data), and devices, your account state may be corrupted on the server side. Contact Anthropic Support by clicking the Support button on the bottom menu within the Claude interface or by visiting support.anthropic.com to file a technical ticket.