How to Debug Google Apps Script: Logger, Breakpoints & Error Handling

Apps Script debugging is split between the in-browser editor, execution transcripts, and optional Cloud Logging for Workspace admins. Unlike Node, you cannot attach a local debugger unless you use clasp and external tooling for limited scenarios.

Most production bugs are authorization drift, trigger type mistakes, or silent empty ranges—not syntax errors. Your first step is always View > Executions and reproducing with a manual run.

This guide walks Logger.log, breakpoints, try/catch patterns, and status-sheet observability. If triggers never fire, start at /blog/google-apps-script-trigger-not-working-fix.

Example code

function debugFetch(url) {
  try {
    const res = UrlFetchApp.fetch(url, { muteHttpExceptions: true });
    Logger.log('HTTP %s body length %s', res.getResponseCode(), res.getContentText().length);
    return res;
  } catch (e) {
    Logger.log('Fetch failed: %s', e.message);
    throw e;
  }
}

FAQ