How to Broadcast Todoist Task Completions to Slack with n8n

n8n Canvas > New Workflow

Create a new n8n workflow

Log into your n8n instance and click the orange 'New Workflow' button in the top right of the canvas. Give it a clear name like 'Todoist → Slack Task Broadcast'. You'll land on a blank canvas with a single grey node labeled 'Start'. You won't use that Start node — you're replacing it with a webhook trigger.

1. 1Click 'New Workflow' in the top-right corner
2. 2Click the workflow title at the top and rename it to 'Todoist → Slack Task Broadcast'
3. 3Click the grey 'Start' node and press the Delete key to remove it

Canvas > + > Webhook

Add a Webhook trigger node

Click the '+' button in the center of the empty canvas to open the node selector. Search for 'Webhook' and select it. In the right panel, set the HTTP Method to POST and note the webhook URL shown — you'll paste this into Todoist in the next step. Set Authentication to 'None' for now (Todoist sends a secret token you can validate later in a code node).

1. 1Click the '+' icon on the empty canvas
2. 2Type 'Webhook' in the search bar and select the Webhook node
3. 3Set HTTP Method to 'POST'
4. 4Copy the 'Test URL' shown in the node panel — you'll need it in Todoist

Todoist Web App > Settings > Integrations > Developer

Register the webhook in Todoist

Todoist doesn't expose webhook settings in its main UI — you register webhooks via their REST API. Open a terminal or use a tool like Postman. You need your Todoist API token from Settings > Integrations > Developer in the Todoist web app. Send a POST request to https://api.todoist.com/sync/v9/webhooks with your token and the n8n webhook URL. Subscribe only to the 'item:completed' event to avoid flooding n8n with unrelated triggers.

1. 1In Todoist, go to Settings > Integrations > Developer and copy your API token
2. 2Open Postman (or curl in a terminal)
3. 3POST to https://api.todoist.com/sync/v9/webhooks with header Authorization: Bearer YOUR_TOKEN
4. 4Set the request body: { "url": "YOUR_N8N_WEBHOOK_URL", "events": ["item:completed"] }
5. 5Confirm the response returns a webhook ID — save it if you need to delete this webhook later

n8n Canvas > Webhook Node > Test Workflow

Capture a test event from Todoist

Back in n8n, click 'Test Workflow' so the Webhook node starts listening. Switch to Todoist and complete any task in any project. Within 2-3 seconds, n8n should receive the event and display the raw payload in the Webhook node's output panel. Expand the data to see the fields Todoist sends — you need content (task name), completed_at, project_id, and user_id.

1. 1Click 'Test Workflow' at the top of the n8n canvas
2. 2Switch to Todoist in another tab
3. 3Mark any task as complete by clicking the circle next to it
4. 4Switch back to n8n and click on the Webhook node to see the incoming data

Canvas > + > Code

Add a Code node to format the message

Click the '+' after the Webhook node and add a 'Code' node. This is where you build the Slack message string from the raw Todoist payload. The Todoist webhook body is nested — the task data lives inside event_data, not at the top level. Write a short JavaScript snippet to extract task name, project ID, and completion time, then format them into a readable Slack message string. See the Pro Tip section for the full code.

1. 1Click '+' after the Webhook node
2. 2Search for 'Code' and select the Code node
3. 3Set the language to JavaScript
4. 4Paste the transformation code from the Pro Tip section below
5. 5Click 'Execute Node' to verify the output shows a formatted message string

Paste this into the first Code node (Step 5). It extracts and normalizes all task fields from Todoist's nested webhook payload, formats the timestamp into human-readable UTC, adds an urgency emoji for priority-4 tasks, and guards against the Todoist verification ping — saving you a separate IF node.

// n8n Code Node — Todoist Task Completion Parser
// Paste into the first Code node after the Webhook trigger
const payload = items[0].json;

// n8n Code Node — Todoist Task Completion Parser
// Paste into the first Code node after the Webhook trigger

const payload = items[0].json;

// Guard against Todoist's webhook verification ping
if (!payload.event_data) {
  return [];
}

const task = payload.event_data;

// Extract core fields
const taskName = task.content || 'Unnamed Task';
const projectId = task.project_id ? task.project_id.toString() : null;
const userId = task.user_id ? task.user_id.toString() : null;
const priority = task.priority || 1; // 1=normal, 2=medium, 3=high, 4=urgent
const description = task.description || '';
const dueDate = task.due ? task.due.date : null;

// Format completion timestamp
const rawTimestamp = task.completed_at || new Date().toISOString();
const completedDate = new Date(rawTimestamp);
const formattedTime = completedDate.toLocaleString('en-US', {
  month: 'short',
  day: 'numeric',
  year: 'numeric',
  hour: '2-digit',
  minute: '2-digit',
  timeZone: 'UTC',
  timeZoneName: 'short'
});

// Determine urgency emoji based on Todoist priority
const priorityEmoji = priority === 4 ? '🔥✅' : '✅';

// Check if task was completed after its due date
let lateFlag = '';
if (dueDate) {
  const due = new Date(dueDate);
  if (completedDate > due) {
    lateFlag = ' _(completed late)_';
  }
}

// Build partial message — project name gets added in the merge Code node (Step 7)
const partialMessage = `${priorityEmoji} *${taskName}* has been completed!${lateFlag}`;

return [
  {
    json: {
      taskName,
      projectId,
      userId,
      priority,
      description,
      formattedTime,
      partialMessage,
      rawTimestamp
    }
  }
];

Canvas > + > HTTP Request

Look up the project name via Todoist API

Add an HTTP Request node after the Code node. Configure it to GET https://api.todoist.com/rest/v2/projects/{{ $json.project_id }} using the Todoist API token in a Bearer Authorization header. This returns the project name so your Slack message reads 'Website Redesign' instead of '2316456789'. Store this result — the next node will merge it with the formatted message.

1. 1Click '+' after the Code node and add an 'HTTP Request' node
2. 2Set Method to GET
3. 3Set URL to https://api.todoist.com/rest/v2/projects/{{ $('Code').item.json.project_id }}
4. 4Add a header: Authorization = Bearer YOUR_TODOIST_API_TOKEN
5. 5Click 'Execute Node' to confirm it returns a name field with the project name

Canvas > + > Code

Merge task data and project name

Add another Code node after the HTTP Request node. Here you combine the formatted message from step 5 with the project name from step 6 to produce the final Slack message. Reference the previous nodes using n8n's $('NodeName').item.json syntax. Build the final message string with emoji, bold task name (using Slack's mrkdwn format), and the resolved project name.

1. 1Click '+' after the HTTP Request node and add a second Code node
2. 2Name it 'Build Final Message' for clarity
3. 3Reference the task name from the first Code node using $('Code').item.json.taskName
4. 4Reference the project name using $('HTTP Request').item.json.name
5. 5Output a single object with a slackMessage field

Canvas > + > Slack > Send a Message

Add the Slack node and connect your workspace

Click '+' after the merge Code node and search for 'Slack'. Select the Slack node and choose 'Send a Message' as the operation. Click 'Create New Credential' and authenticate via OAuth2 — this opens Slack's authorization screen where you'll approve the connection. You need the channels:write and chat:write OAuth scopes granted. n8n will store the token after you approve.

1. 1Click '+' after the second Code node
2. 2Search for 'Slack' and select the Slack node
3. 3Set Operation to 'Send a Message'
4. 4Click 'Credential for Slack API' > 'Create New'
5. 5Complete the OAuth flow in the popup window and click Allow

Slack Node > Parameters > Channel + Message

Configure the Slack message destination and body

In the Slack node, set Channel to the channel where completed tasks should broadcast — type the channel name like #project-wins. For the message text, reference the slackMessage field from your merge Code node using the expression {{ $json.slackMessage }}. Enable 'Use Blocks' only if you want richer formatting — for most teams, plain mrkdwn text in the Message field is enough and faster to set up.

1. 1In the Channel field, type the target channel name (e.g. #project-wins)
2. 2Click the expression toggle (the lightning bolt icon) next to the Message field
3. 3Type {{ $json.slackMessage }} in the expression editor
4. 4Leave 'As User' unchecked unless you want the message to appear from your personal account
5. 5Click 'Execute Node' to send a test message to Slack

n8n Canvas > Webhook Node > Production URL > Active Toggle

Activate the workflow with the Production URL

Before activating, go back to the Webhook node and copy the Production URL (not the Test URL). Update your Todoist webhook registration — make a DELETE request to remove the old webhook, then POST a new one with the Production URL. Back in n8n, click the 'Active' toggle in the top right of the canvas to turn the workflow on. Todoist will now send completed task events to the production endpoint.

1. 1Click the Webhook node and copy the 'Production URL'
2. 2In Postman or curl, DELETE the existing Todoist webhook: DELETE https://api.todoist.com/sync/v9/webhooks/YOUR_WEBHOOK_ID
3. 3Register a new Todoist webhook with the Production URL using the same POST request as Step 3
4. 4In n8n, click the grey 'Inactive' toggle in the top-right corner to set the workflow to Active
5. 5Complete a task in Todoist and confirm the Slack message fires within 5 seconds