Fix: Claude Network Error When Sending Message

When Claude displays a red "network error" banner or modal while you are sending a message, it means the connection between your browser and Anthropic’s message-streaming servers was broken mid-request. Unlike a complete system outage, this error often occurs due to Server-Sent Events (SSE) timeouts, browser resource limits, aggressive local security software, or heavy prompt payloads.

Because Claude streams responses token-by-token, it relies on a continuous, uninterrupted connection. Any micro-drop in network packets can trigger a network error. Follow these steps to diagnose and fix the issue.

Step 1: Reduce Prompt Payload and File Upload Sizes Massive context sizes are a common trigger for network errors. If you upload large PDFs, CSVs, or long codeblocks, the server may take too long to process the initial prompt, causing the connection to time out before the stream begins. 1. **Split your files:** Instead of uploading a single 10MB document, split it into three or four smaller sections. 2. **Clear chat history:** Start a new chat conversation. Extremely long chat histories require Claude to re-evaluate thousands of tokens on every new turn, increasing processing latency and the probability of an SSE timeout. 3. **Simplify the prompt:** Send a brief message first, then paste your context in smaller increments once the connection is established.

Step 2: Disable Browser Extensions Intercepting WebSockets and SSE Certain extensions monitor, modify, or block real-time web traffic, leading to abrupt disconnection states. 1. **Adblockers and Privacy Tools:** Extensions like uBlock Origin, Privacy Badger, or Brave Shields can falsely flag the streaming endpoints of Claude (`api.anthropic.com` or backend streams) as tracking scripts. 2. **Grammar and Translation Tools:** Extensions like Grammarly, LanguageTool, or Google Translate actively hook into text areas and dynamically modify the DOM. This can disrupt Claude's script execution when sending messages. 3. **Test in Guest Mode:** Open a guest profile in your browser (which disables all extensions by default) and test sending a message. If it succeeds, disable your extensions one by one in your main profile to identify the culprit.

Step 3: Check for Network Protocol and WebSocket Blockers Some local networks, firewalls, or VPN protocols do not support persistent HTTP connections or Server-Sent Events. 1. **VPN Protocol Adjustment:** If you use a VPN, switch the protocol from OpenVPN (which can have higher packet loss on unstable networks) to WireGuard, or temporarily disconnect the VPN entirely. 2. **Antivirus Web Shields:** Security suites (such as Avast, Bitdefender, or Kaspersky) inspect HTTPS traffic in real-time. This inspection can delay packet delivery enough to break streaming connections. Temporarily disable "Web Shield" or "HTTPS Scanning" in your antivirus settings to test. 3. **Disable Proxy Settings:** Ensure your operating system does not have manual proxy servers configured that might buffer or terminate long-lived connections.

Step 4: Configure Browser Resource Management Modern browsers employ aggressive memory-saving features that suspend or throttle background tabs and socket connections. 1. **Chrome Memory Saver:** Go to `chrome://settings/performance` and disable **Memory Saver**, or add `claude.ai` to the **Always keep these sites active** list. 2. **Keep the Tab Active:** Avoid switching tabs immediately after hitting send. Keep the Claude tab in the foreground until the model finishes generating its complete response.

When to escalate If you continue to get network errors across multiple distinct browser profiles, different internet networks (such as switching from office Wi-Fi to a mobile hotspot), and even with short prompts, the issue likely resides with Claude's internal message-queuing infrastructure. Check `status.anthropic.com` for active incidents involving "degraded performance" or "increased error rates." If no incident is reported, contact Anthropic support with details on your payload size and the specific browser console log errors (e.g., `ERR_CONNECTION_CLOSED` or `ERR_EMPTY_RESPONSE`).