Google Apps Script Slack Integration: Send Messages & Read Channels

Beyond incoming webhooks, Slack's Web API enables posting to channels, reading history, and uploading files from Apps Script with bot tokens stored securely.

Use chat.postMessage with channel ID, not display name, and include blocks for structured alerts. Scopes must match bot installation: chat:write, channels:read, etc.

Sheet row notifications often use webhooks (/blog/google-sheets-send-slack-notification); this guide covers full API access.

Example code

function slackPostMessage(channelId, text) {
  const token = PropertiesService.getScriptProperties().getProperty('SLACK_BOT_TOKEN');
  const res = UrlFetchApp.fetch('https://slack.com/api/chat.postMessage', {
    method: 'post',
    contentType: 'application/json',
    headers: { Authorization: 'Bearer ' + token },
    payload: JSON.stringify({ channel: channelId, text: text }),
  });
  const data = JSON.parse(res.getContentText());
  if (!data.ok) throw new Error(data.error);
  return data.ts;
}

FAQ