Auto-Summarize Blog Posts to Social Media with Gemma and Postiz

Overview

This workflow automatically monitors an RSS feed (e.g., a blog), fetches the latest post, generates a concise summary and relevant hashtags using a local LLM (Ollama with Gemma), extracts an image from the post, and publishes the content to multiple social media platforms (Facebook, LinkedIn, X/Twitter, Instagram) via the Postiz API. It includes duplicate detection to avoid reposting the same content and runs on a schedule (every 10 minutes).

This is ideal for bloggers, content creators, or marketers who want to maintain an active social media presence without manual effort. By leveraging a local LLM, you keep your data private and avoid API costs, while Postiz centralizes posting to multiple platforms from a single workflow.

Node-by-Node Breakdown

1. Schedule: Check RSS Every 10 Minutes (No auth) — Triggers the workflow every 10 minutes. Configured with an interval rule: every 10 minutes.

2. Set RSS Feed URLs (No auth) — Sets the RSS feed URL as a string variable. Configured with a single assignment: Blog's Name = https://blogsname.blogspot.com/feeds/posts/default.

3. Split RSS Feed URLs into Items (No auth) — Splits the incoming data by the field Blog's Name to create individual items for each feed URL.

4. Fetch Latest RSS Feed Content (No auth) — Reads the RSS feed from the configured URL. Configured with url = https://blogsname.blogspot.com/feeds/posts/default.

5. Loop Over RSS Items for Processing (No auth) — Iterates over each RSS item in batches. Configured with default options.

6. Merge Processed Data Streams (No auth) — Combines data from two branches (RSS fetching and image processing) by position, including unpaired items.

7. Select Latest RSS Item by Date (No auth) — JavaScript code node that sorts all items by pubDate descending and returns only the most recent one.

8. Calculate Link Hash for Duplication Check (No auth) — JavaScript code node that computes a simple hash of the post link to use for duplicate detection.

9. Read Last Posted Hash from File (No auth) — JavaScript code node that reads the previously posted link hash from a file at /.n8n/rss_last_posted.txt.

10. Compare Hashes for Duplicate Check (No auth) — JavaScript code node that compares the current link hash with the last posted hash and sets shouldProceed flag. Also logs to a debug file.

11. Conditional Check for New Post (No auth) — JavaScript code node that filters out items where shouldProceed is false, effectively stopping the workflow for already-posted content.

12. Normalize RSS Fields (Content & Link) (No auth) — Set node that extracts and normalizes contentSnippet and link fields from the RSS item.

13. Calculate Summary Character Limit (No auth) — JavaScript code node that calculates the maximum characters available for the summary (280 minus link length, buffer, and hashtag reserve).

14. Generate Summary and Hashtags with LLM (No auth) — LangChain LLM chain node that sends a prompt to the local Ollama model. The prompt instructs the model to summarize the content in under maxChars characters, append 3 hashtags and the link.

15. Configure Local LLM Model (Ollama) (No auth) — Configures the Ollama language model with model gemma3:12b. Requires a local Ollama instance running.

16. Process LLM Output for Postiz (Extract Text/Hashtags/Link) (No auth) — JavaScript code node that parses the LLM output, extracting the text, hashtags, and link. Falls back to default hashtags if parsing fails.

17. Save Temporary Link Hash to File (No auth) — JavaScript code node that writes the current link hash to a temporary file (/.n8n/rss_temp_url.txt) for later use.

18. Validate Inputs for Postiz API (No auth) — JavaScript code node that validates that text, link, image ID, and image path are all present before posting.

19. Create and Post Content via Postiz API (Postiz API auth) — HTTP Request node that sends a POST request to the Postiz API (https://postiz.selfhosteddomain.net/api/public/v1/posts) with the content, image, and platform settings for Facebook, LinkedIn, X/Twitter, and Instagram. Uses postizApi credential type.

20. Save Posted Hash to File (No auth) — JavaScript code node that writes the successfully posted link hash to /.n8n/rss_last_posted.txt to prevent future duplicates.

21. Fetch Blog Post HTML Content (No auth) — HTTP Request node that fetches the full HTML of the blog post to extract an image. Configured to return response as text.

22. Extract Image URL from Post HTML (No auth) — JavaScript code node that parses the HTML to find the first image URL using regex.

23. Filter Latest Item for Image Processing (No auth) — JavaScript code node that filters items with valid image URLs and takes only the latest one.

24. Download Post Image (No auth) — HTTP Request node that downloads the image from the extracted URL. Configured to return response as a file.

25. Transform/Resize Image for Upload (No auth) — Edit Image node that resizes the image to 1080x1080 pixels and converts to JPEG format.

26. Upload Image to Postiz (Postiz API auth) — Postiz node that uploads the resized image to Postiz using the binary data from the previous node.

Setup Instructions

Prerequisites

• n8n instance (self-hosted or cloud)
• Ollama running locally with the gemma3:12b model (or another compatible model)
• Postiz account (self-hosted or cloud) with API access
• Blog RSS feed URL (e.g., Blogger, WordPress, Medium)

Credentials Needed

1. Postiz API — Create an API key in your Postiz dashboard under Settings > API. Add as a credential in n8n.
2. Ollama — No credentials needed if running locally; just ensure the Ollama service is accessible from n8n.

Configuration Steps

1. Replace the RSS feed URL in the Set RSS Feed URLs node with your blog's RSS feed URL.
2. Update the Configure Local LLM Model (Ollama) node with your Ollama endpoint if not running on the default.
3. In the Create and Post Content via Postiz API node, replace the integration IDs with your actual Postiz integration IDs for each platform (Facebook, LinkedIn, X, Instagram).
4. Update the Postiz API URL if self-hosted.
5. Ensure the file paths (/.n8n/rss_last_posted.txt, /.n8n/rss_temp_url.txt, /.n8n/debug_log.txt) are writable by n8n.
6. Activate the workflow.

Use Cases and Variations

Primary Use Case

Automatically repurpose blog content to social media with AI-generated summaries, ensuring consistent posting without manual effort.

Variations

• Different LLM: Swap gemma3:12b for other Ollama models like llama3, mistral, or phi.
• Different Platforms: Add or remove platform integrations in the Postiz API payload.
• Custom Prompt: Modify the LLM prompt for different tones (professional, humorous, etc.) or different hashtag counts.
• Image Handling: Change image resize dimensions or format, or skip image entirely.
• Scheduling: Adjust the trigger interval (e.g., hourly, daily) or add time-based conditions.
• Multiple Blogs: Extend the Set RSS Feed URLs node to include multiple feeds and loop over them.
• Error Handling: Add error handling nodes (e.g., Slack notification on failure).

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