App Logs

View real-time logs from your running App. Debug requests, errors, and tool calls as they happen.

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mctx streams live logs from your App directly to the dashboard. Logs are real-time only — there is no log history or retention. No configuration required.

Accessing Logs

Navigate to your App detail page (/dev/servers/[id])
Click View Logs in the Server Information section
The log modal opens and begins streaming immediately
Trigger a request to your App to see logs appear

Requirement: Your App must be in Live status. Logs are not available for Apps that are not live.

What Gets Logged

Any console.* call in your App code appears in the log stream:

Method	Level	Use Case
`console.log()`	Info	General operational events
`console.info()`	Info	Informational messages
`console.warn()`	Warn	Warnings and potential issues
`console.error()`	Error	Errors and failures
`console.debug()`	Debug	Detailed debugging info

export default {
  async fetch(request: Request, env: Env): Promise<Response> {
    console.log(`[INFO] ${request.method} ${request.url}`);

    try {
      const result = await processRequest(request, env);
      console.log("[INFO] Request processed successfully");
      return result;
    } catch (error) {
      console.error(`[ERROR] Request failed: ${error.message}`);
      throw error;
    }
  },
};

No Retention

Logs are not stored. They are only visible while the log modal is open. Closing the modal discards all buffered output — you cannot retrieve past logs.

If you need to review logs after the fact, send them to an external service (see Persistent Logging below).

Log Best Practices

Use consistent prefixes

Prefixes make it easy to filter and scan logs in the modal:

console.log("[INFO] Tool called: weather-lookup");
console.log("[DEBUG] Parameters: " + JSON.stringify(params));
console.warn("[WARN] Rate limit approaching: " + remaining + " requests left");
console.error("[ERROR] API call failed: " + error.message);

Log the request lifecycle

console.log("[INFO] " + request.method + " request received");
console.log("[INFO] Tool: " + toolName + ", Params: " + JSON.stringify(params));
console.log("[INFO] External API: " + apiUrl);
console.log("[INFO] Response status: " + response.status);

Never log secret values

// Bad — exposes the secret
console.log("Using API key: " + env.API_KEY);

// Good — confirms it is present without revealing it
console.log("Using API key: " + env.API_KEY.slice(0, 4) + "...");

Add timing to spot bottlenecks

const start = Date.now();
const result = await callExternalApi(query);
console.log("[INFO] API call completed in " + (Date.now() - start) + "ms");

Choose the right level

Level	When to Use
`DEBUG`	Detailed information for troubleshooting
`INFO`	Normal operational events
`WARN`	Something unexpected but not an error
`ERROR`	Error conditions that should be investigated

Persistent Logging

For logs you need to keep, send them to an external service from your App code:

async function logToExternal(message: string, level: string, env: Env) {
  await fetch("https://logs.example.com/ingest", {
    method: "POST",
    headers: {
      Authorization: `Bearer ${env.LOGGING_API_KEY}`,
      "Content-Type": "application/json",
    },
    body: JSON.stringify({
      timestamp: Date.now(),
      level,
      message,
    }),
  });
}

Services that work well with Cloudflare Workers:

Axiom — High-volume log analytics
Datadog — Full observability platform
Better Stack (Logtail) — Developer-focused logging
New Relic — Application performance monitoring