Generate Instagram Captions from Hashtag Analysis using Apify + GPT-4o-mini

Description

This n8n workflow scrapes recent Instagram posts by hashtag and generates new, relevant caption ideas using OpenAI. It avoids making up suggestions by analyzing real-world content and surfacing common patterns.

✅ Use Case

Marketing teams, content creators, or social media managers can:

Discover what’s trending for a specific topic
Automatically generate Instagram captions based on real posts
Understand common caption styles for a niche
Save time brainstorming ideas while staying on-brand

🧠 How It Works

1️⃣ Manual Trigger

🧩 Node: When clicking ‘Execute workflow’
Manually starts the workflow for testing or single-run execution.

2️⃣ Define the Hashtag

🧩 Node: Create Search Term
Sets the value of the hashtag you'd like to scan.
Default is n8n, but you can modify it to anything.

{
"Search_Term": "yourCustomHashtag"
}

3️⃣ Scrape Instagram Posts

🧩 Node: Find Recent Posts
API**: Apify Instagram Hashtag Scraper
Setup**:
Visit Apify Console
Create an API token
In n8n, go to Credentials and add HTTP Query Auth
Use ?token=yourTokenHere as the query string

JSON Body:
{
"hashtags": ["{{ $json.Search_Term }}"],
"resultsLimit": 20,
"resultsType": "posts"
}

4️⃣ Extract Captions

🧩 Node: Set bio and follower count
Extracts just the caption from each post and stores it in a clean variable for the AI agent to use.

5️⃣ Aggregate Captions

🧩 Node: Aggregate
Gathers all captions into one list before processing.
Useful for passing a large text block into the AI.

6️⃣ Convert to Single Text Block

🧩 Node: Convert table names and columns into single text for agent
Uses a Code node to combine all captions into a single string for OpenAI to read:
return [
{
json: {
text: items
.map(item => - ${JSON.stringify(item.json)})
.join('\n\n'),
},
},
];

7️⃣ Generate Caption Ideas with AI

🧩 Node: AI Agent
Takes the combined post text and sends it to GPT-4o-mini.
Includes this system message:
I'm looking for ideas for posts about {{ $('Create Search Term').item.json.Search_Term }}.
Here’s the last 5 posts on Instagram about the topic. Use those to help me generate a list of relevant captions.

Do not make up ideas that are not like the others in the list.

Output like this:
{
"Post Idea": ["Idea1", "Idea2"],
"Most Common Post": ["common post 1", "common post 2"]
}

8️⃣ Choose Language Model

🧩 Node: OpenAI Chat Model
Model**: gpt-4o-mini
Credential**: Use your OpenAI API key.
Get it from: OpenAI API Keys
Add it in n8n under OpenAI credentials.

9️⃣ Parse the AI Output

🧩 Node: Structured Output Parser
Parses the GPT response into structured JSON:
{
"Post Idea": ["Idea1", "Idea2"],
"Most Common Post": ["common post 1", "common post 2"]
}

🔟 Split the Outputs

🧩 Nodes: Split Out, Split Out1
Separates the Post Idea list and Most Common Post list into individual items.

🔁 Merge for Final Output

🧩 Node: Merge
Combines the two split lists into one output stream.

👤 Need More Help?

Robert Breen
Automation Consultant | AI Workflow Designer | n8n Expert
📧 [email protected]
🔗 LinkedIn