Payment Processing APIs: pricing compared
5 providers · normalized effective rate per online transaction · June 2026 snapshot
Payment APIs charge a percentage of each transaction plus a fixed fee. Because the fixed fee dominates on small charges and the percentage dominates on large ones, the cheapest provider depends on your average order value. We show both the headline rate and the effective cost on common ticket sizes. On its headline metric, Braintree is generally the cheapest (2.59% + $0.49 per online transaction), but the best value depends on your volume and feature needs.
Source: Vendor published pricing pages. Data as of June 2026.
Payment Processing APIs compared
| Provider | Headline rate | Fee on $20 | Fee on $100 | Best for |
|---|---|---|---|---|
| Stripe | 2.9% + $0.30 per online card transaction | $0.88 (4.4%) | $3.20 (3.2%) | Developers and platforms that want the best API, broad payment methods and Connect for marketplaces. |
| Square | 2.9% + $0.30 per online transaction | $0.88 (4.4%) | $3.20 (3.2%) | Small businesses that sell both in person and online and want hardware + software bundled. |
| Braintree | 2.59% + $0.49 per online transaction | $1.01 (5.05%) | $3.08 (3.08%) | Businesses that want PayPal/Venmo acceptance but a card-style percentage rather than the wallet rate. |
| PayPal | 3.49% + $0.49 per standard online transaction | $1.19 (5.95%) | $3.98 (3.98%) | Merchants who want instant buyer trust and PayPal/Venmo as a checkout option. |
| Adyen | ~$0.13 processing fee + interchange + scheme fees (interchange++) | varies | varies | Larger enterprises with volume to negotiate, who want transparent interchange++ and one global platform. |
Vendor pricing as of June 2026 — verify on the vendor pricing page. Rates are for US online (card-not-present) transactions. The effective rate = (percent x amount + fixed fee) / amount. Interchange++ providers (Adyen) pass network fees through at cost, so their effective rate varies with your card mix. International cards and currency conversion add surcharges everywhere.
How we compare
Rates are for US online (card-not-present) transactions. The effective rate = (percent x amount + fixed fee) / amount. Interchange++ providers (Adyen) pass network fees through at cost, so their effective rate varies with your card mix. International cards and currency conversion add surcharges everywhere.
Provider notes
Stripe — 2.9% + $0.30 per online card transaction
The developer standard. Headline rate matches Square online; cheaper than PayPal Checkout on a typical sale. Surcharges for international and currency conversion.
Free tier: No monthly fee; pay per transaction.
Square — 2.9% + $0.30 per online transaction
Best known for in-person POS; online rate matches Stripe. Strong fit for omnichannel small businesses; less of a pure developer/API story.
Free tier: No monthly fee; pay per transaction.
Braintree — 2.59% + $0.49 per online transaction
A PayPal-owned gateway with a lower percent than standard PayPal Checkout but a higher fixed fee ($0.49). Good middle ground for accepting both cards and PayPal.
Free tier: No monthly fee; pay per transaction.
PayPal — 3.49% + $0.49 per standard online transaction
The standard PayPal rate is the highest of the group on a typical sale, but buyer recognition can lift conversion. Card-processing tiers are cheaper than the wallet rate.
Free tier: No monthly fee; pay per transaction.
Adyen — ~$0.13 processing fee + interchange + scheme fees (interchange++)
Interchange++ can be cheaper than flat 2.9% for businesses with favorable card mixes and volume, but the effective rate is variable, not a single headline number. Verify with a quote.
Free tier: No monthly fee; interchange++ pricing.
Head-to-head matchups
- Stripe vs PayPal — cheaper on price: Stripe
Frequently asked questions
What is the cheapest payments API in 2026?
Braintree is generally the cheapest payments option on its headline metric (2.59% + $0.49 per online transaction). The best value depends on your volume and feature needs — Rates are for US online (card-not-present) transactions. The effective rate = (percent x amount + fixed fee) / amount. Interchange++ providers (Adyen) pass network fees through at cost, so their effective rate varies with your card mix. International cards and currency conversion add surcharges everywhere.
How do you compare payments API pricing fairly?
We normalize each provider to a common unit (effective rate per online transaction). Rates are for US online (card-not-present) transactions. The effective rate = (percent x amount + fixed fee) / amount. Interchange++ providers (Adyen) pass network fees through at cost, so their effective rate varies with your card mix. International cards and currency conversion add surcharges everywhere. Always confirm current pricing on the vendor's page, since rates change.
Which payment processor is cheapest, the percentage or the fixed fee?
It depends on your average order value. The fixed fee (e.g. $0.30 or $0.49) dominates on small charges, while the percentage dominates on large ones. Use the payment fee calculator to compare providers at your typical ticket size.
Source & accuracy
Each figure is a snapshot of the named vendor's public pricing page, captured in June 2026. Trademarks belong to their owners. API pricing changes frequently — verify on the vendor's pricing page before relying on these numbers. Derived figures are computed with the transparent formulas described in our methodology.
Last updated: 2026-06-18