How to Send Todoist Deadline Alerts to Slack with n8n

n8n Canvas > + New Workflow

Create a new n8n workflow

Open your n8n instance and click the orange 'New Workflow' button in the top right of the canvas. Give the workflow a name like 'Todoist Deadline → Slack'. You'll land on an empty canvas with a single gray trigger node placeholder. This is where you'll build the entire flow from left to right.

1. 1Click '+ New Workflow' in the left sidebar or top navigation
2. 2Click the pencil icon next to 'My Workflow' and rename it to 'Todoist Deadline → Slack'
3. 3Click the gray trigger node placeholder in the center of the canvas

Canvas > Trigger Node > Schedule Trigger

Add a Schedule trigger

Search for 'Schedule' in the node picker and select the Schedule Trigger node. Set the interval to every 15 minutes. This is the heartbeat of your workflow — it wakes the workflow up at regular intervals to check Todoist for approaching or overdue deadlines. Avoid setting this below 5 minutes; Todoist's REST API enforces rate limits and unnecessary polling adds no value.

1. 1Type 'Schedule' in the node search panel
2. 2Click 'Schedule Trigger' from the results
3. 3Set 'Trigger Interval' to 'Minutes'
4. 4Set the interval value to '15'
5. 5Click 'Back to Canvas'

Canvas > + Node > Todoist > Credentials > Create New

Connect your Todoist account

Click the '+' button to the right of the Schedule Trigger to add the next node. Search for 'Todoist' and select the Todoist node. In the parameters panel, click 'Create New Credential'. You'll be prompted to enter a Todoist API token — find this under Todoist Settings > Integrations > Developer > API token. Copy the token and paste it into n8n, then click 'Save'.

1. 1Click the '+' connector on the right edge of the Schedule Trigger
2. 2Search 'Todoist' in the node picker
3. 3Select 'Todoist' from the results
4. 4Click 'Credential for Todoist API' dropdown and select 'Create New'
5. 5Paste your Todoist API token into the 'API Token' field
6. 6Click 'Save' to store the credential

Todoist Node > Resource: Task > Operation: Get All > Filters

Configure Todoist to fetch tasks with due dates

With the Todoist node selected, set the Resource to 'Task' and the Operation to 'Get All'. Under Filters, add a filter for 'Filter' and enter the Todoist filter string: 'overdue | today'. This uses Todoist's native filter syntax to return all tasks that are due today or already past due. Leave the limit at 100 unless your team has unusually large projects.

1. 1Set 'Resource' to 'Task'
2. 2Set 'Operation' to 'Get All'
3. 3Toggle on 'Additional Fields'
4. 4In the 'Filter' field type: overdue | today
5. 5Leave 'Limit' at 100

Canvas > + Node > Code

Add a Code node to calculate urgency and format messages

Add a Code node after the Todoist node. This is where you calculate whether each task is overdue or due today, assign urgency labels, and build the Slack message text. Paste the JavaScript below into the code editor. The code iterates over every returned task, computes the difference between today's date and the task's due date, and tags each task as OVERDUE or DUE TODAY before passing it downstream.

1. 1Click the '+' connector on the Todoist node
2. 2Search 'Code' in the node picker and select the Code node
3. 3Set 'Language' to 'JavaScript'
4. 4Set 'Mode' to 'Run Once for All Items'
5. 5Paste the pro tip code into the code editor
6. 6Click 'Test Step' to verify output

Paste this into the first Code node (Step 5). It runs once for all items, computes urgency and days overdue, resolves assignee IDs to Slack usernames via a hardcoded map (replace with your team's IDs), and builds the full Slack message string. The second block handles deduplication using n8n's static workflow data — paste that into the second Code node (Step 6).

// ── CODE NODE 1: Urgency calculation + message formatting ──
// Mode: Run Once for All Items
const items = $input.all();

// ── CODE NODE 1: Urgency calculation + message formatting ──
// Mode: Run Once for All Items

const items = $input.all();
const today = new Date();
today.setHours(0, 0, 0, 0);

// Replace these with your actual Todoist assignee_id → Slack username mappings
const assigneeMap = {
  '38291047': '@sarah.chen',
  '38291055': '@marcus.okafor',
  '38291062': '@james.liu',
};

const priorityLabels = {
  4: 'Urgent',
  3: 'High',
  2: 'Normal',
  1: 'Low',
};

const results = [];

for (const item of items) {
  const task = item.json;

  // Skip tasks with no due date
  if (!task.due || !task.due.date) continue;

  const dueDate = new Date(task.due.date);
  dueDate.setHours(0, 0, 0, 0);

  const diffMs = today - dueDate;
  const diffDays = Math.floor(diffMs / (1000 * 60 * 60 * 24));

  let urgencyLabel;
  let emoji;

  if (diffDays > 0) {
    urgencyLabel = `OVERDUE (${diffDays} day${diffDays === 1 ? '' : 's'})`;
    emoji = '⚠️';
  } else if (diffDays === 0) {
    urgencyLabel = 'DUE TODAY';
    emoji = task.priority === 4 ? '🔴' : '📌';
  } else {
    // Not due yet — skip (remove this block if you want upcoming tasks too)
    continue;
  }

  const assignee = assigneeMap[task.assignee_id] || 'Unassigned';
  const priority = priorityLabels[task.priority] || 'Normal';
  const formattedDue = dueDate.toLocaleDateString('en-US', { month: 'short', day: 'numeric', year: 'numeric' });

  const slackMessage = [
    `${emoji} *${urgencyLabel}* — ${task.content}`,
    `📅 Due: ${formattedDue} | Priority: ${priority}`,
    `👤 Assignee: ${assignee}`,
    `🔗 ${task.url}`,
  ].join('\n');

  results.push({
    json: {
      task_id: task.id,
      task_name: task.content,
      due_date: task.due.date,
      days_overdue: diffDays,
      urgency_label: urgencyLabel,
      assignee_slack: assignee,
      slack_message: slackMessage,
    },
  });
}

return results;


// ── CODE NODE 2: Deduplication using static workflow data ──
// Mode: Run Once for All Items
// Paste this into the SECOND Code node

/*
const items = $input.all();
const staticData = $getWorkflowStaticData('global');

// Initialize the notified IDs store if it doesn't exist
if (!staticData.notifiedIds) {
  staticData.notifiedIds = [];
}

const newItems = [];
const newlyNotified = [];

for (const item of items) {
  const taskId = item.json.task_id;
  if (!staticData.notifiedIds.includes(taskId)) {
    newItems.push(item);
    newlyNotified.push(taskId);
  }
}

// Add newly notified IDs to the store
staticData.notifiedIds = [...staticData.notifiedIds, ...newlyNotified];

// Cap the store at 500 IDs to prevent unbounded growth
if (staticData.notifiedIds.length > 500) {
  staticData.notifiedIds = staticData.notifiedIds.slice(-500);
}

return newItems;
*/

Canvas > + Node > Code (second instance)

Add a deduplication check with n8n's Static Data

To avoid spamming Slack with the same task every 15 minutes, add a second Code node that uses n8n's $getWorkflowStaticData() to store IDs of tasks already notified. On each run, the node filters out tasks whose IDs are already in the static data store and only passes new ones downstream. It then updates the store with the newly notified IDs. Tasks are cleared from the store once they no longer appear in the Todoist filter (meaning they were completed or rescheduled).

1. 1Click the '+' connector on the first Code node
2. 2Add another Code node
3. 3Set Mode to 'Run Once for All Items'
4. 4Paste the deduplication logic from the pro tip code's second function
5. 5Click 'Test Step' and verify only new task IDs pass through

Canvas > + Node > Slack > Credentials > OAuth2

Connect your Slack account

Add a Slack node after the deduplication Code node. Click 'Create New Credential' and select 'OAuth2'. n8n will open a pop-up to authorize your Slack workspace. Sign in and grant the requested permissions — you need chat:write and channels:read at minimum. If you want to post to private channels, also grant chat:write.customize and the bot must be invited to those channels manually.

1. 1Click '+' after the deduplication Code node
2. 2Search 'Slack' and select the Slack node
3. 3Click 'Credential for Slack API' and choose 'Create New'
4. 4Select 'OAuth2 (recommended)'
5. 5Click 'Connect my account' and authorize in the Slack pop-up
6. 6Select your workspace and click 'Allow'

Slack Node > Resource: Message > Operation: Send

Configure the Slack message node

With the Slack node selected, set Resource to 'Message' and Operation to 'Send'. For 'Channel', type the exact channel name including the '#' symbol (e.g. #project-deadlines). In the 'Text' field, click the expression toggle (the '{ }' icon) and reference the slack_message field from the Code node output: {{ $json.slack_message }}. This injects the formatted message text built in Step 5.

1. 1Set 'Resource' to 'Message'
2. 2Set 'Operation' to 'Send'
3. 3Enter your target channel name in 'Channel' (e.g. #project-deadlines)
4. 4Click the expression toggle '{ }' next to the 'Text' field
5. 5Type: {{ $json.slack_message }}
6. 6Optionally set 'Username' to 'Deadline Bot' for a cleaner display name

Todoist Node > ... menu > Add Error Output > connect to Slack (alerts channel)

Add error handling with a Stop and Error node

Click the three-dot menu on the Todoist node and select 'Add Error Output'. Connect the error output to a Slack node configured to post to a #workflow-alerts or #ops channel with the message 'Todoist Deadline workflow failed: {{ $json.message }}'. Do the same for the Slack node itself. This means if the Todoist API is down or your Slack token expires, you get notified instead of silently missing deadline alerts.

1. 1Right-click the Todoist node and select 'Add Error Output'
2. 2Connect the red error output connector to a new Slack node
3. 3Configure that Slack node to post to your internal alerts channel
4. 4Set the message text to: 'Deadline workflow error: {{ $json.message }}'
5. 5Repeat for the main Slack node's error output

Canvas > Test Workflow button (top right)

Test end-to-end with a real Todoist task

Create a test task in Todoist with today's date as the due date. Go back to n8n and click 'Test Workflow' (not 'Execute Workflow' — that saves first). Watch each node light up green as data flows through. Verify the Slack message appears in your channel with the correct task name, due date, and urgency label. Check that running the test a second time produces no duplicate Slack message, confirming deduplication works.

1. 1Create a Todoist task titled 'TEST: Deadline check' due today
2. 2Return to n8n and click the 'Test Workflow' button
3. 3Watch each node turn green as execution proceeds
4. 4Verify the message appears in Slack within 30 seconds
5. 5Click 'Test Workflow' again and confirm no duplicate message is sent

Canvas > Active/Inactive toggle (top right)

Activate the workflow

Click the gray 'Inactive' toggle in the top right of the canvas to switch it to 'Active'. n8n will immediately schedule the first execution based on your 15-minute interval. The workflow will now run automatically without you needing to keep the browser open. Check the 'Executions' tab after 30 minutes to confirm the first scheduled run completed successfully.

1. 1Click 'Save' to save the workflow
2. 2Click the 'Inactive' toggle to flip it to 'Active'
3. 3Confirm the toggle turns green and shows 'Active'
4. 4Navigate to the 'Executions' tab in the left sidebar
5. 5Wait 15 minutes and refresh — you should see a completed execution entry