How Do Price Drop Alerts Actually Work?
A look at the technology behind price drop alerts: web scraping, check frequencies, alert triggers, and the trade-offs between browser extensions and web apps.
Price drop alerts notify you when a product you want hits a lower price. Instead of refreshing product pages, a tool watches for you and sends a notification when the price changes.
Here's how the whole process works, from scraping to alerts.
How do price trackers check prices?
Price trackers pull data from product pages using one of three methods: web scraping, retailer APIs, or browser extensions.
Web scraping loads the product page and extracts the price from the HTML. This is the most flexible approach because it works on any website with a public product page. Tools like Slasher use AI-powered scraping to read prices the same way a human would.
Retailer APIs connect directly to a store's data feed. Amazon's Product Advertising API is the most common example. The upside is reliability. The downside is that you are locked to one retailer.
Browser extensions read the page while you browse. They inject code into the page to grab the price in real time. This only works while your browser is open and the extension is active.
How often do prices get checked?
Frequency varies by tool and by plan.
Most free tools check once per day. That's enough to catch sales that last a day or longer, which covers the majority of price drops. Slasher runs daily price checks at 6am UTC so your dashboard is fresh every morning.
Premium tools may check hourly or even every few minutes. This matters for flash sales or limited-time deals. For most purchases, daily checks are more than sufficient.
Some browser extensions only check when you visit the page. Which defeats the purpose.
What triggers an alert?
Price alert tools use one or more of these trigger conditions:
Fixed threshold. You set a target price. When the product drops to or below that number, you get notified. This is the most common setup and the easiest to understand.
Any price change. The tool notifies you whenever the price moves in either direction. Useful for volatile products where you want to understand pricing patterns before buying.
Percentage drop. You set a percentage, like 10%. If the price drops by that amount relative to the original or recent price, the alert fires. This works well when you do not have a specific dollar amount in mind.
Slasher lets you set a target price per product. When the daily check finds the price at or below your threshold, you get an email alert.
Browser extension vs. web app vs. email alerts
Each delivery method has tradeoffs.
Browser extensions are convenient when you are already shopping. You can add products with one click. The downside: they only work in one browser, they slow down page loads, and they stop working if you switch devices or uninstall the extension.
Web apps run independently of your browser. You add a product URL once and the tool tracks it in the cloud. This works across all your devices. Slasher takes this approach. Paste a URL, set your target price, and the server handles everything from there.
Email alerts are the delivery layer, not the tracking method. Most tools (including Slasher) use email to push notifications. Some also offer push notifications, SMS, or in-app alerts. Email remains the most reliable because it requires no installation.
Can I track prices on any website?
Most popular price trackers only work with Amazon. Tools like CamelCamelCamel, Keepa, and Honey are built around Amazon's product catalog. If you shop at other stores, they cannot help.
Slasher works differently. It uses AI-powered web scraping to extract prices from any product page on any website. Paste the URL of a product from Target, Best Buy, Walmart, a niche electronics store, or any other retailer. If the page shows a price, Slasher can track it.
This matters because the best deal is not always on Amazon. Price tracking should follow the product, not the store.
Are price trackers accurate?
Price trackers are reliable for straightforward products, but there are edge cases to know about.
Variant pricing. A product page might show different prices for different sizes, colors, or configurations. The tracker reads whatever price is visible by default, which may not match the variant you want.
Out-of-stock products. When a product goes out of stock, the price might disappear from the page or change to a third-party seller price. This can create false signals in the price history.
Dynamic pricing. Some retailers show different prices based on your location, login status, or browsing history. Scrapers see the default price, not a personalized one. This is usually an advantage because you get the baseline price without manipulation.
Page layout changes. If a retailer redesigns their product page, scrapers may need to adapt. AI-powered scraping (like Slasher uses through Firecrawl) handles this better than rule-based scrapers because it reads the page contextually rather than relying on fixed HTML selectors.
No tracker is perfect. But for catching real sales and avoiding impulse purchases, they pay for themselves fast.
Start tracking prices now
Slasher lets you track any product from any store. Paste a URL, set your target price, and get notified when the price drops. No browser extensions, no Amazon lock-in, no manual checking.
For a comparison of the tools available and which works best for your shopping style, see Keepa vs CamelCamelCamel vs Slasher and Best Price Tracker Browser Extensions in 2026, Ranked.
Track prices before you buy
Paste any product URL and Slasher tracks the price daily. Get notified when it drops.
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