Coupons that don't blow up your checkout.
PromoStack is the API-first promotion engine for indie SaaS — coupons, stacking rules, and fraud-safe redemption through one clean API.
Built for indie SaaS
API-first
No credit card to start
Homegrown promo code always breaks the same three ways.
The spreadsheet-and-if-statements approach works right up until the first real campaign.
Stacking surprises
Two codes at one checkout and your homegrown logic applies them in an order nobody planned. Discounts multiply, margins evaporate.
Race conditions at checkout
Two requests hit the same coupon at the same moment and both succeed. A 1-use code redeems twice because the check-and-apply wasn't atomic.
Glue code everywhere
Validation logic copy-pasted into every checkout path. Every promo campaign ships with a little anxiety and a lot of manual review.
One engine for every kind of promotion.
Coupons are live today. Gift cards, referrals, loyalty, and fraud controls are coming next — all through the same API.
Coupons
Percentage, fixed-amount, and free-shipping codes with explicit stacking rules, caps, and expiry windows.
Learn more
Gift Cards
Stored-value cards with partial redemption and a full balance ledger — not a hacked-together coupon.
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Referrals
Double-sided rewards where the advocate and the friend both win, with fraud screening built in.
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Loyalty
Points, tiers, and VIP treatment with earn/burn rules and a ledger you can actually audit.
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Fraud
Velocity limits, blocklists, and a review queue for flagged redemptions — abuse stays out without blocking good customers.
Learn more
Try a real redemption right now.
This playground fires a live redemption against the demo merchant — same API, same idempotency, no signup.
Try it live — no signup
This hits a real demo merchant — each click is a new redemption.
curl -X POST /v1/redeem \
-H "Authorization: Bearer $PROMOSTACK_KEY" \
-H "Idempotency-Key: $(uuidgen)" \
-d '{
"codes": ["WELCOME10"],
"customerRef": "playground-visitor",
"orderTotal": 100
}'Live in three steps.
From signup to your first redemption in minutes — here's the whole integration.
Get an API key
Sign up and create a scoped key from your dashboard. It takes under a minute — no sales call, no credit card.
Create a coupon
Define the code, the discount, and the rules. Stacking, caps, and windows are explicit — not tribal knowledge.
Validate & redeem
Check a code before checkout, then redeem it atomically. One idempotency key makes retries safe by construction.
curl -X POST /v1/redeem \
-H "Authorization: Bearer $PROMOSTACK_KEY" \
-H "Idempotency-Key: $(uuidgen)" \
-d '{
"codes": ["WELCOME10"],
"customerRef": "cus_123",
"orderTotal": 100
}'
# → 200 {"discount": 10, "total": 90, "redemptions": ["WELCOME10"]}Pricing that respects indie math.
Start free. Upgrade when the revenue justifies it. Billed through Paddle — no credit card to start.
Free
For side projects getting started.
$0forever
- Coupon validation & redemption API
- Idempotent retries
- Community support
Starter
Most popularFor indie SaaS finding traction.
$29/month
- Everything in Free
- Stacking rules & priorities
- Multiple API keys
- Email support
Growth
For scaling revenue.
$79/month
- Everything in Starter
- Higher redemption volume
- Usage analytics
- Priority support
Fair questions.
Stripe coupons cover the basics — one code per checkout and no real stacking control. The moment you need two promotions to combine safely, like a welcome discount plus a seasonal sale, Stripe leaves you to hand-roll the logic and hope it doesn't double-apply. PromoStack exists for exactly that: explicit stacking rules, priority ordering, and idempotent redemption so retries never discount twice.
Voucherify is a strong product — priced for enterprises at around €600/month. PromoStack is built for indie SaaS from day one: the same core engine (coupons, stacking, fraud-safe redemption) at roughly 5% of that price, API-first, with no sales call required to get started.
PromoStack computes the discount on the order total and returns the adjusted amount; tax and VAT are applied downstream by your billing provider. Since we bill through Paddle — which acts as the merchant of record — EU/UK VAT and other sales taxes are handled for you automatically.
Ship your first promotion today.
No credit card to start. Create a coupon, redeem it from the playground, and see the whole engine in under five minutes.