A crypto swap API lets your wallet or payment app quote an exchange, create an order and track it to payout without holding the user's funds. Providers differ most on three things: what you earn, how long a quote stays valid, and what their docs admit about failures. Below: a comparison table and a 12-point integration checklist.
The Fswap partner API documents both rate types — rateType: "MARKET" for floating and "FIXED" — and credits your per-key percentage only on orders that reach FINISH, calculated on the USDT value of the payout (Fswap API docs, October 2026).
SimpleSwap sets each API key's fee at 0.4% by default and lets partners raise it, with payouts in USDT once rewards pass 300 USDT (SimpleSwap public API guide).
StealthEX lets partners set a commission anywhere between 0 and 0.5%, and describes integration as free with "no monthly fees, paid plans, or call limits" (StealthEX, 2026).
ChangeNOW publishes hard rate limits — 1,800 calls per minute and 30 per second — across 1,300+ coins on 100+ networks (ChangeNOW for partners).
The on-chain route charges you instead of paying you: 0x lists its Standard plan at $1,000 with a 0.15% transaction fee and a 5 requests-per-second limit (0x pricing).
Provider risk is not theoretical. LetsExchange ceased exchange operations on October 1, 2026, with support available only through November 30 (LetsExchange notice). One hard-coded provider is one point of failure.
A crypto exchange API for a wallet replaces four screens with four calls: list the supported coins, quote a pair, create an order, then poll its status until payout. The user's funds never touch your servers — they go to a deposit address the provider issues, and the payout goes straight to the address your user typed.
Two architectures sit behind that same shape, and they behave differently:
Instant-swap (off-chain) APIs route each order to a liquidity provider or exchange. They cover coins across unrelated chains — Monero, Bitcoin, Tron, TON — and can offer a fixed rate, because a provider is taking the price risk. The Fswap API, for example, routes each quote across up to nine liquidity providers and returns the one it will honour.
On-chain aggregator APIs build a transaction your user signs from their own wallet. They cover millions of tokens but only within the chains they support, settle in one block, and never fix a rate — the quote is an estimate until the transaction lands.
The practical split: an instant-swap API handles cross-chain pairs and gives you a number you can show with confidence. An on-chain API handles long-tail tokens on one chain and hands the execution risk to the user. If that distinction is new, our explainer on P2P, DEX and DeFi exchange models covers the underlying mechanics.
The column that decides most integrations is the last but one. Everything else is roughly comparable; what you actually get paid, and whether the provider commits to a number, is not.
Provider | Assets claimed | Fixed rate | End-user account | Your commission | Docs and limits |
|---|---|---|---|---|---|
Fswap API | Live list from | Yes — | None to swap; AML policy applies | Fixed percentage per API key ( | Public docs + OpenAPI JSON; documents every error code, retry rules and test order IDs |
2,800+ cryptocurrencies | Yes — | None — "sign-up is not required" | 0.4% per key by default, partner can raise it; USDT payout above 300 USDT | v3 API, | |
2,000+ crypto, 100+ fiat | Yes — floating or fixed | None to swap | Partner sets 0–0.5% | Public API docs + Postman; states no call limits | |
1,300+ coins, 100+ networks | Yes — separate fixed-rate methods | None to swap; checks when AML triggers | Partner rates "start from 0.4%" | Postman docs, | |
10M+ tokens, 150+ liquidity sources | No — on-chain quote, expires | No account; user signs on-chain | You set | Full reference + dashboard key; 5 RPS on Standard | |
1,000+ crypto assets | Yes — "fixed and floating rates to choose from" | None to swap; checks when AML triggers | "Up to 50% revenue share"; base commission not published | Keys on request; docs not linked from the business page | |
3,600+ coins, 675 networks, 40+ integrated partners | Not stated on the B2B page | None to swap | "Built-in rev share" — no figure published | Public docs; sign up for an API key |
Ordered by how precisely each provider's public documentation defines what you get paid — from an exact per-key percentage with a stated calculation basis and crediting rule, down to a revenue-share claim with no base figure. Asset counts are each provider's own published figure as checked on October 9, 2026; they are self-reported, counted differently (coins vs. tokens vs. networks) and not independently verified. Fswap publishes no catalogue figure in its API docs, so the live endpoint is cited instead.
Off-chain, cross-chain, crypto-to-crypto only. A quote returns a rateCalcId valid for two hours on floating rates and five minutes on fixed; the deposit window is 120 minutes and 15 minutes respectively. Its docs state plainly that claims/create has no idempotency key, that an invalid API key is silently processed without attribution, and that reading an order has no ownership check — the kind of detail most providers leave you to discover in production.
A v3 REST API with ten request types, keyed by x-api-key. The fee per key starts at 0.4% and you can raise it, with the explicit caveat that doing so moves the rate your user sees. Fiat exchanges stay locked at 0.4%. Payouts unlock at 300 USDT.
Coverage of 2,000+ cryptocurrencies and 100+ fiat currencies, with commission set by the partner between 0 and 0.5%. Public docs plus a Postman collection, and no paid tiers or call quotas to manage — a reasonable default for a small wallet that wants predictable cost.
1,300+ coins across 100+ networks and over 2,250,000 pairs, with fixed-rate handled through separate endpoints rather than a flag. The only provider here that publishes concrete throughput: 1,800 calls per minute, 30 per second. Partner rates start from 0.4% and are negotiated.
Liquidity from 150+ sources and access to 10M+ tokens, with built-in monetization through swapFeeBps and swapFeeRecipient (default cap 1,000 bps, i.e. 10%). The trade-off is cost and scope: the Standard plan is listed at $1,000 with a 0.15% transaction fee and 5 requests per second, and every swap stays within the chains 0x supports.
1,000+ assets with both rate types and an advertised "up to 50% revenue share", plus CPA, CPI and hybrid models. The base commission that the 50% applies to is not published, and the business page links no API reference — you request keys and get terms through a conversation.
An aggregator rather than a single venue: 3,600+ coins across 675 networks sourced from 40+ integrated partners including CEXs, DEXs and off-chain liquidity. That breadth is the point, and it also means your user's order may land with any of those partners, each with its own refund behaviour. Rev share is mentioned without a figure.
Start from what your users actually swap, not from the biggest coin count. Five questions settle it:
Cross-chain or single-chain? If users want BTC to Monero or TON to USDT, an on-chain aggregator cannot help you at all. If they want a long-tail ERC-20, an instant-swap API probably does not list it.
Do you need to show a guaranteed number? Payment and invoicing flows do. That rules out on-chain quotes and makes fixed-rate support non-negotiable — along with accepting the shorter deposit window that comes with it.
Is your commission a published number or a conversation? A documented per-key percentage you can reconcile beats a "up to 50%" headline you cannot model.
Who carries custody? Non-custodial routing keeps you out of holding user funds, which changes your operational and compliance picture entirely. Our breakdown of custodial vs non-custodial exchanges sets out the difference.
What happens when it breaks? Read the error table before the feature list. A provider that documents refunds, expiry and retry semantics is telling you it has handled those cases.
For a cross-chain, account-free integration where you need both rate types and a reconcilable payout, the Fswap API is a direct fit: one API key in the x-user-api-key header, a fixed commission per key built into the quote, rewards credited in USDT within minutes of an order reaching FINISH, and a documented health endpoint to monitor. You can see the pair coverage on the popular pairs page before writing any code, and the same rails handle business flows described in our guide to crypto for B2B payments.
These are the failure modes that produce support tickets rather than error logs. Each one is drawn from behaviour the providers above document.
Send the same credential on quote and create. Fswap rejects an order whose API key differs from the one used for the quote, and credits nothing when the key is missing from either call.
Respect the quote's time to live. Two hours for floating, five minutes for fixed on Fswap. Re-quote rather than retrying an expired identifier.
Set your HTTP timeout to at least 15 seconds. A quote polls several liquidity providers live and can take around 10 seconds. Do not fire parallel duplicates.
Never blindly retry order creation. There is no idempotency key, so a repeated call after a timeout can create a second order. Repeat once at most, then look the order up.
Persist the order ID before you render anything. On an unauthenticated call it is the only handle on the order; lose it and the order is unreachable through the public API.
Treat that order ID as a secret. Fswap's lookup endpoint performs no ownership check, so anyone holding the ID can read addresses, hashes and amounts.
Collect the memo or destination tag when the asset needs one. The coin list flags it; extra IDs are passed through unvalidated, and a missing one can strand a payout.
Validate the payout address against the receiving network first. Use the address-validation endpoint, and treat a true result as "not rejected" rather than a guarantee.
Handle non-OK statuses that arrive as HTTP 200. Amount-below-minimum and rate-unavailable are statuses, not errors — show the returned limits instead of a generic failure.
Surface the deposit deadline and the confirmation count. Both come back in the quote. Most "my swap is stuck" tickets are just unconfirmed deposits — see why a swap sits pending.
Keep the key server-side. A partner key with account access can withdraw a balance and read other keys. It never belongs in web or mobile client code.
Test against fixtures and monitor the health endpoint. Fswap answers reserved test order IDs with each status from a fixture, and exposes a health check safe to poll — wire both before launch, and keep a fallback provider configured.
An interface that lets an application quote and execute a crypto-to-crypto exchange programmatically. Your app calls four endpoints — coin list, rate, create order, order status — and the provider handles liquidity, the deposit address and the payout.
Integrating requires only an account with the provider and an API key; none of the instant-swap providers above require your end users to register to swap. Your own obligations depend on your jurisdiction and what your product does, and every provider still runs AML screening and can request verification on a flagged transfer.
A fixed quote locks the amount the user receives, in exchange for a shorter deposit window — on Fswap, 15 minutes against 120 for a floating quote. A floating quote recalculates at execution, so the user may receive more or less than the estimate.
Typical partner commissions sit between 0 and 0.5% of swap volume. SimpleSwap's own worked example puts roughly 80,000 USDT of monthly volume at 320 USDT at the 0.4% default, or 480 USDT at 0.6%. Raising your margin raises revenue per swap and worsens the rate your user sees.
No. A partner API key generally grants account access, not just quoting, so it must stay on your backend. Proxy the calls through your own server and never ship the key in client code.
The order expires or is refunded, depending on the provider and whether a deposit arrived. Fixed-rate orders often require a refund address for exactly this reason, so collect one at order creation rather than after something goes wrong.
Among the instant-swap options, SwapSpace claims the widest coverage at 3,600+ coins across 675 networks, because it aggregates 40+ other providers. On-chain, 0x reaches 10M+ tokens, but only within the chains it supports and without a fixed rate.
Pick the architecture first — cross-chain and quotable, or single-chain and on-chain — then choose on the two things that are hard to change later: whether the provider commits to a payout number you can reconcile, and whether its documentation tells you what happens when a swap fails. Coin counts are marketing; error tables are engineering.
Ready to integrate? The Fswap partner API documents both rate types, every error code and reserved test order IDs — start with the API reference and request a key.
Elena leads marketing at Fswap and writes about cryptocurrency exchange: how swaps work, how to compare rates and fees, and how to keep funds safe without unnecessary KYC.
