Build a Price Tracker in 10 Minutes with Crawlstack

Price trackers are one of the most useful things you can build for yourself — and one of the most annoying to set up with traditional scraping tools. Headless browsers, proxy services, cron jobs, databases. It adds up fast.

This tutorial builds a working price tracker using Crawlstack, which runs directly in your browser. No server required. Total time: about 10 minutes.

What We're Building

A crawler that:

• Visits a product page (or a list of product pages)
• Extracts the product name and current price
• Stores results in a local dataset with deduplication and versioning
• Can be re-run on a schedule to track price changes over time

Prerequisites

• Crawlstack installed (browser extension or Docker)
• A product URL you want to track

Step 1: Open the Crawlstack Creator

Navigate to the product page you want to track. Open DevTools (F12 or Cmd+Option+I) and click the Crawlstack tab.

Click New Crawler and give it a name — something like price-tracker.

Step 2: Inspect the Price Element

Before writing any code, use the DevTools Elements panel to find the CSS selector for the price. On most e-commerce sites, the price is in a predictable element.

Right-click the price on the page → Inspect. Note the class or ID. For example:

.product-price
#priceblock_ourprice
[data-testid="price"]

Do the same for the product title.

Step 3: Write the Extraction Script

Back in the Crawlstack Creator, paste this script:

await onLoad();

const title = document.querySelector('h1')?.innerText?.trim();
const price = document.querySelector('.product-price')?.innerText?.trim();

if (!title || !price) {
  console.warn('Could not find title or price — check your selectors');
  return;
}

await runner.publishItems([{
  // key ensures deduplication per URL
  key: location.href,
  // version tracks changes over time — we use the price as the version
  version: price,
  data: {
    title,
    price,
    url: location.href,
    scrapedAt: new Date().toISOString()
  }
}]);

Update .product-price and h1 with the actual selectors from Step 2.

Step 4: Test It

Click Test Run. You should immediately see your item appear in the Items panel on the right:

{
  "title": "Outdoor Tent Pro 3000",
  "price": "$249.99",
  "url": "https://example-store.com/products/outdoor-tent",
  "scrapedAt": "2026-03-13T10:42:00.000Z"
}

If nothing appears, open the Logs tab — it'll tell you if the selector didn't match anything.

Step 5: Enable Change Tracking

The version field is doing important work here. Crawlstack uses it to detect when an item has changed. If you re-run the crawler and the price is the same, the item won't be duplicated — it'll be marked as unchanged. If the price drops to $199.99, a new version of the item is stored.

This means your dataset becomes a price history, not just a snapshot.

Step 6: Track Multiple Products

To track a list of products, you can seed the crawler with multiple URLs. Create a simple task list at the start of your script:

const { taskDef } = await runner.getCurrentTask();

// First run: seed the product URLs
if (!taskDef.ctx?.type) {
  const productUrls = [
    'https://example-store.com/products/tent',
    'https://example-store.com/products/sleeping-bag',
    'https://example-store.com/products/hiking-boots',
  ];

  await runner.addTasks(productUrls.map(href => ({
    href,
    ctx: { type: 'product' }
  })));
  return;
}

// For each product page
await onLoad();

const title = document.querySelector('h1')?.innerText?.trim();
const price = document.querySelector('.product-price')?.innerText?.trim();

await runner.publishItems([{
  key: location.href,
  version: price,
  data: { title, price, url: location.href, scrapedAt: new Date().toISOString() }
}]);

Step 7: Export or Access via API

Once you've run the crawler, your data is available in three ways:

Export as CSV or JSON — click the Download button in the Crawlstack panel. Perfect for pasting into a spreadsheet.

SQLite — the full dataset lives in a local SQLite file you can query directly.

Public API relay — if you've enabled the HTTP tunnel, you can hit your data programmatically:

GET /crawler/price-tracker/items

This lets you build a simple notification script that polls the API and sends you an alert when a price changes.

What's Next

• Schedule the crawler to run automatically using Crawlstack's monitoring features
• Add AI filtering to extract prices from inconsistently structured pages (useful when selectors vary across sites)
• Extend to scrape an entire category page and automatically discover new products to track

The full script from this tutorial is available as a template on GitHub — you can deploy it to your own Crawlstack instance in one click.

Crawlstack is a self-hosted scraping infrastructure that runs inside your browser or Docker. Get started for free.