Published at

How to Monitor Subreddits for Keywords with Cloudflare Workers

Learn how to use monitor Reddit for posts containing target keywords

Authors
  • avatar
    Name
    AJ Dichmann
    Twitter
  • VP of Digital Strategy at Globe Runner
Table of Contents

If you are into automation and want to stay ahead of online giveaways on Reddit, using a Cloudflare Worker to track Reddit posts and Discord webhooks for notifications is a great (free) solution to never miss a giveaway.

In this post I will show you how to set up a Cloudflare Worker that scans a subreddit for giveaway-related keywords and sends alerts to a Discord channel—all without running a dedicated server or monthly fees so baseball card lovesr like me never miss a Reddit giveaway.

Why Use a Cloudflare Worker?

Cloudflare Workers provide a lightweight, low-latency, and cost-effective way to run scripts on the edge. Instead of constantly polling Reddit with a traditional server setup, a worker can be triggered on demand (with a cron job in this case), fetching data efficiently.

Plus, Cloudflare Workers are free, easy to set up and manage - plus they run on Javascript so the code is easy to write

What We’re Building

We are going to build a Cloudflare Worker that:

  1. Fetch the latest posts from a subreddit using the .new.json endpoint.
  2. Scan for keywords like "giveaway", "give away", and "contest".
  3. Send a Discord notification when a match is found, tagging a specific user.
  4. Add the title and link of the giveaway post in an embedded format.

Writing the Cloudflare Worker Script

Step 1: Fetch Subreddit Posts

Reddit provides a JSON API that lets us fetch recent posts from any subreddit. Here’s the API endpoint for the 50 latest posts in r/baseballcards:

https://www.reddit.com/r/baseballcards/new.json?limit=50

Later in the code we will loop through these posts using a for() loop and check if the title contains any of the keywords we are looking for.

Step 2: Match Giveaway Keywords

We use regular expressions to identify posts containing “giveaway”, “give away”, or “contest” in their title or body.

const SEARCH_PATTERNS = [/giveaway/i, /give away/i, /contest/i];

Step 3: Send Notifications to Discord

If a post matches, we send a webhook message to Discord. The webhook will:

  • Tag @ajd to notify a specific user (note: this must be a userid, not the username).
  • Include an embedded message with the giveaway details.

Here’s the full script:

export default {
  async fetch(request) {
    const SUBREDDIT_NAME = "baseballcards"; // Change to your subreddit
    const SEARCH_PATTERNS = [/giveaway/i, /give away/i, /contest/i]; 
    const REDDIT_URL = `https://www.reddit.com/r/${SUBREDDIT_NAME}/new.json?limit=50`;
    const DISCORD_WEBHOOK_URL = "add your webhook url here!"; // Add your Discord webhook URL here

    try {
      const response = await fetch(REDDIT_URL, {
        headers: { "User-Agent": "CloudflareWorker/1.0" }
      });

      if (!response.ok) {
        return new Response(`Error fetching subreddit data: ${response.statusText}`, { status: 500 });
      }

      const data = await response.json();
      const posts = data.data.children;
      let foundPosts = [];

      for (let post of posts) {
        const title = post.data.title.toLowerCase();
        const selfText = post.data.selftext.toLowerCase();

        if (SEARCH_PATTERNS.some(pattern => pattern.test(title)) || SEARCH_PATTERNS.some(pattern => pattern.test(selfText))) {
          const postUrl = `https://www.reddit.com${post.data.permalink}`;
          foundPosts.push({ title: post.data.title, url: postUrl });

          // Send notification to Discord tagging @ajd
          await fetch(DISCORD_WEBHOOK_URL, {
            method: "POST",
            headers: { "Content-Type": "application/json" },
            body: JSON.stringify({
              content: "<@ajd> 🎉 Giveaway Alert!",
              username: "Reddit Giveaway Bot",
              avatar_url: "https://www.redditinc.com/assets/images/site/reddit-logo.png",
              embeds: [{
                title: `🎁 Giveaway Alert in r/${SUBREDDIT_NAME}!`,
                description: `**${post.data.title}**\n[View Post](${postUrl})`,
                color: 16776960 
              }]
            })
          });
        }
      }

      return new Response(JSON.stringify(
        foundPosts.length > 0 ? { found: true, posts: foundPosts } : { found: false, message: "No matching posts found" },
        null, 2
      ), { headers: { "Content-Type": "application/json" } });

    } catch (error) {
      return new Response(`Error: ${error.message}`, { status: 500 });
    }
  }
};

Deploying to Cloudflare

Step 1: Create a New Worker

  1. Log into Cloudflare and navigate to Workers & Pages.
  2. Click Create a Service and select HTTP Handler.
  3. Paste the script into the Cloudflare Workers Editor.
  4. Set the execution frequency to “Every 30 minutes”

Step 2: Set Up the Discord Webhook

  1. In Discord, go to Server Settings > Integrations > Webhooks.
  2. Click New Webhook, give it a name, and copy the Webhook URL.
  3. Replace DISCORD_WEBHOOK_URL in the script with your copied webhook.

Step 3: Deploy

  1. Click Save and Deploy.

How It Works

  • 🚀 Every time the worker runs, it fetches new Reddit posts
  • 🔍 It searches for giveaways using keyword matching
  • 📢 When a match is found, a Discord alert is sent

Example Discord Notification:

@ajd 🎉 Giveaway Alert!
🎁 Giveaway Alert in r/baseballcards!
🚀 "Win a free baseball card!"
🔗 [View Post](https://www.reddit.com/r/baseballcards/comments/xyz123)

This setup is a FREE, low-maintenance way to monitor Reddit for giveaways and get instant alerts on Discord. It’s serverless, real-time, and scalable.

Sharing is caring!