Auto Instagram Carousel from Canva via Webhook with AI Caption

Auto Instagram Carousel from Canva via Webhook with AI Caption

High-Level Summary

This workflow automates the process of turning Canva carousel slide exports into fully published Instagram posts with AI-generated captions. When a webhook payload containing PNG slides (e.g., from Claude Cowork or a Canva automation) is received, the workflow uploads each image, uses OpenAI to generate an optimized Instagram caption, and publishes the carousel via Blotato. It eliminates manual downloading, caption writing, and posting — ideal for social media managers, content creators, and agencies running Instagram at scale.

Node-by-Node Breakdown

1. Webhook (No auth) — Listens for incoming POST requests at the path canva-pngs-to-drive. This is the trigger that receives the carousel slide data (expected as a JSON payload with a body.slides array containing slide objects, each with an export_url field).

2. Split Out Slides (No auth) — Splits the incoming body.slides array into individual items. This allows each PNG slide to be processed independently for upload.

3. Upload media (Blotato API key auth — uses a Blotato credential) — For each slide, uploads the image URL ($json.export_url) to Blotato's media hosting service. The resource is set to media.

4. Aggregate (No auth) — Collects all the uploaded image URLs from the previous step into a single array. This aggregates the url field from each item so the full carousel can be posted together.

5. Caption Generator (OpenAI API key auth — uses an OpenAI credential) — Sends two messages to the OpenAI model (GPT-5-MINI):

   • System prompt: Sets the agent as a caption generator for "Soulfit Pilates"
   • User prompt: Asks the model to "Create an effective caption for Soulfit Pilates. Output only the caption and hashtags without other marks or explanations." The AI response is stored and used later as the Instagram caption.

6. Send message and wait for response (Telegram bot token auth — uses a Telegram credential) — Sends a Telegram message to the specified chatId containing a preview of the carousel (5 image URLs) and the AI-generated caption. The operation is sendAndWait with approvalType set to double (two-step approval). This pauses the workflow until the user approves or rejects via Telegram buttons.

7. If (No auth) — Checks the approval response from Telegram. If $json.data.approved is true (user approved), the workflow proceeds to publish. Otherwise, it goes to the rejection branch.

8. Create post (Blotato API key auth) — Publishes the Instagram carousel post using Blotato. The accountId is set to a placeholder (REPLACE_WITH_YOUR_ACCOUNT_ID). The post content text comes from the AI caption ($('Caption Generator').item.json.output[0].content[0].text), and media URLs come from the aggregated array ($('Aggregate').item.json.url).

9. Send a text message (Telegram bot token auth) — If the user rejects the post, sends a Telegram message: "Got it. In that case, please check your Canva files" to the same chat.

10. No Operation, do nothing (No auth) — A no-op node that does nothing. Used as a terminal node for the rejection branch.

Setup Instructions

Prerequisites

• n8n instance (self-hosted or cloud)
• OpenAI API key — Get one here
• Blotato account — Sign up at blotato.com and connect your Instagram account
• Telegram bot — Create one via BotFather and get the bot token
• A webhook sender (e.g., Claude, Canva automation, or custom script) that sends POST requests with the payload format:

  {
    "body": {
      "slides": [{"export_url": "https://example.com/slide1.png"}, ...]
    }
  }
  

Configuration Steps

1. Import the workflow into n8n.
2. Replace the following placeholders:
   • REPLACE_WITH_YOUR_ACCOUNT_ID in the Create post node with your actual Blotato account ID
   • REPLACE_WITH_YOUR_ACCOUNT_ID in both Telegram nodes with your Telegram chat ID
3. Configure these credentials in n8n:
   • OpenAI — API Key credential
   • Blotato — API Key credential
   • Telegram — Bot Token credential
4. Activate the workflow and copy the Webhook URL (e.g., https://your-n8n.example.com/webhook/canva-pngs-to-drive).
5. Configure your upstream tool to send POST requests to that URL with the expected payload format.
6. Test by sending a sample payload.

Use Cases & Variations

Perfect for:

• Social media managers automating Instagram carousel posts from design tools
• Content creators producing daily carousels at scale
• Agencies managing multiple Instagram accounts with automated workflows
• AI-assisted content pipelines where captions are generated dynamically

How to adapt:

• Change the brand: Edit the prompts in the Caption Generator node to match your brand voice instead of "Soulfit Pilates"
• Add more slides: The carousel supports any number of slides (the aggregate just collects them)
• Replace Telegram approval: Swap with email approval, Slack, or remove approval entirely by connecting the AI caption directly to Create post
• Use different trigger: Replace the Webhook with a Schedule trigger to pull from a Google Sheet or database
• Post to other platforms: Blotato supports LinkedIn, Twitter/X, and Facebook — change the account in the Create post node
• Integrate with Canva API: Connect to Canva's export endpoint to automatically send designs to this webhook

Production considerations:

• Add error handling (Try/Catch nodes) to handle failed uploads
• Consider rate limiting if posting to Instagram multiple times per hour
• The current AI prompt outputs only the caption — add validation or a second AI pass for hashtag optimization

{
  "id": "WeTQeLFfZ0ywfhHf",
  "name": "Claude Canva Files → Blotato",
  "tags": [],
  "nodes": [
    {
      "id": "node-wh-001",
      "name": "Webhook",
      "type": "n8n-nodes-base.webhook",
      "position": [
        64,
        304
      ],
      "parameters": {
        "path": "canva-pngs-to-drive",
        "options": {},
        "httpMethod": "POST"
      },
      "typeVersion": 2
    },
    {
      "id": "node-split-002",
      "name": "Split Out Slides",
      "type": "n8n-nodes-base.splitOut",
      "position": [
        256,
        304
      ],
      "parameters": {
        "options": {},
        "fieldToSplitOut": "body.slides"
      },
      "typeVersion": 1
    },
    {
      "id": "a7ad2268-9a28-4220-b930-341a3b2374b2",
      "name": "Upload media",
      "type": "@blotato/n8n-nodes-blotato.blotato",
      "position": [
        432,
        304
      ],
      "parameters": {
        "mediaUrl": "={{ $json.export_url }}",
        "resource": "media"
      },
      "typeVersion": 2
    },
    {
      "id": "d2b2f286-7c5c-423a-a33e-a646454997aa",
// ... truncated (copy to see full JSON)