Coupon extensions promise something simple: install once, and every checkout finds you a discount. Some deliver. Some mostly deliver for their makers. This guide explains what happens behind that "Apply coupons" button, how these tools get paid, and how to choose one that actually lowers what you pay.
The three kinds of shopping extension
1. Code testers. At checkout, the extension takes a list of codes for that store and types them into the promo code box one by one, keeping the one that gives the biggest discount. The list comes from the company's database, which is built from deal sites, user submissions and partnerships with stores.
2. Cash back and rewards. These don't change the price at checkout. You activate them before buying, the store pays the company a commission, and you get part of it back later as cash or points.
3. Store-specific tools. Built for one marketplace, they can do things a general tool can't: read that store's own coupon pages, collect seller coupons, or understand its particular coupon rules. Price-history trackers for AliExpress fall in this group too.
Many popular extensions combine the first two.
What happens when you click "Apply"
A well-built code tester does roughly this:
- Recognises the checkout page of a store it supports.
- Reads the current total from the page.
- Picks candidate codes, ideally only ones that are current and that your order qualifies for.
- Types each code into the store's own promo box and clicks the store's own Apply button, exactly as you would.
- Reads the new total after each attempt.
- Keeps the best result and shows you what you saved.
Step 5 is where tools differ most. On many stores, "code accepted" means "you paid less." On marketplaces like AliExpress and DHgate it doesn't always: one promo code per order, competing with coupons already applied, means an accepted code can leave your total unchanged or even raise it. A good tool compares the total, not the acceptance message.
How coupon extensions make money
Almost all free coupon extensions earn affiliate commissions. When you buy after using the extension, the store pays the extension's maker a percentage of the sale. It doesn't cost you anything; it comes out of the store's marketing budget.
Affiliate income became controversial after allegations, from late 2024, that some extensions replaced other people's referral links at checkout even when they found no coupon. In response, the Chrome Web Store changed its policy in 2025. Extensions may now use affiliate links only when:
- the affiliate program is disclosed to users;
- the user takes an action first, such as clicking a button;
- that action gives the user a direct benefit, like a coupon or discount.
Google's own example: an extension must not insert an affiliate link if no coupon or discount is found. That is a useful yardstick for any extension you're considering.
Are coupon extensions safe?
A coupon extension needs to read the checkout page, which includes your order. That makes permissions the main thing to check:
- Narrow is better. An extension for one store should only ask for access to that store's pages. "Read and change all your data on all websites" is a lot of trust to hand over.
- Read the privacy disclosure on the store listing. Every extension now has to state what data it collects and whether it's sold.
- Install only from official stores: the Chrome Web Store, Microsoft Edge Add-ons or Firefox Add-ons.
A five-point test for any coupon extension
- Does it compare your total before and after? If it only reports "code applied", it may be keeping codes that don't help.
- Are its codes current for your country? Region-specific stores need region-specific codes.
- Is the affiliate relationship disclosed in the listing and the extension itself?
- Are the permissions limited to the stores it supports?
- Does it leave you in control? It should act when you click, and never place or pay for an order on its own.
A myth worth retiring: "secret coupons only for you"
Some extensions and websites claim to unlock "exclusive, account-specific coupons" that nobody else can see. Be sceptical. Stores do give individual accounts coupons, such as new-user offers or rewards, but those already appear in your account and at checkout. An extension can help you collect and combine the coupons available to you; it can't conjure hidden ones.
Where Coupanda fits
We make two free, store-specific extensions, built around the "compare the total" rule:
- AutoAli for AliExpress: collects store coupons for every seller in your cart, applies the best promo code for your country and currency, and only keeps it if your total goes down.
- DHgate Auto Coupon: tries this month's DHgate codes, biggest first, and keeps whichever result gives the lowest total.
Both only ask for access to their own store's pages (plus our own site for the code list), disclose our affiliate commission in the listing, the popup and on the page, and never place an order. If you'd rather apply codes yourself, the same code lists are public: DHgate codes and AliExpress coupons.