Best Fraud Detection APIs in 2026: 10 Compared

A signup farm running Kameleo behind a Bright Data exit does not look dangerous to an IP reputation score, and a stolen card at a returning customer's checkout does not look dangerous to a device fingerprint. The ten APIs below each answer a different question, which is why "best" is the wrong first word and "for which loss" is the right one. We compared them on what they return, what they publish about price and latency, and how to test them with the same six sessions. Every vendor figure links to the page it came from, read on 29 August 2026; where a vendor publishes nothing, or a page refused our fetch, the cell says so.

What each API is for

The ten sort into five categories. The category fixes what the product can see and what it cannot.

IP reputation: IPQS and MaxMind minFraud

IPQS returns a per-address fraud_score with proxy, VPN and Tor flags (IPQS proxy detection docs); minFraud scores a whole transaction per query, with anonymizer flags down to is_residential_proxy (minFraud response docs). Both key on the address and its history, and the blind spot follows: a residential exit with no history scores clean, a carrier NAT shared by thousands of phones can score dirty, and neither sees the browser. See IPQS vs Maskbreak and minFraud vs Maskbreak.

Identity enrichment: SEON

SEON takes an email, a phone number, an IP and a device session and returns a fraud_score and a state of APPROVE, REVIEW or DECLINE (SEON Fraud API reference). It answers whether the applicant exists: mailbox age, carrier data, social footprint. That is the identity question, not the session question; an antidetect profile submitting a real, bought identity passes the parts that lean on enrichment. See SEON vs Maskbreak.

Transaction risk: Sift, Forter and Kount

Sift scores the events you send and returns one 0 to 100 score per abuse type, with reasons (Sift Score API docs). Forter approves or declines each transaction at checkout and lists Chargeback Recovery among its products (Forter on AWS Marketplace). Kount prices by quote on transaction volume (Kount pricing); its developer docs answered 403 to our fetch on 30 August 2026, so we do not describe its response. All three improve with history and are thinnest on first touch: a guest checkout from a device nobody has seen has little to score against, and none was built to tell headless Chromium from a person. See Sift, Forter and Kount against Maskbreak.

Bot perimeter: DataDome and Arkose Labs

DataDome sits in front of the application as a server module or CDN integration plus a JavaScript tag (DataDome getting started) and answers per request; its nginx module documents 200, 403 or 5xx on timeout, with retries disabled (nginx module docs). Arkose runs a client script that produces a session token, and a Verify API that returns a risk_band with device and IP intelligence (Arkose Verify API fields). Both stop automation at the door. Neither knows that the human who passed the challenge is on their fortieth account. See DataDome alternatives and Arkose vs Maskbreak.

Device identity and per-request verdicts: Fingerprint, Castle and Maskbreak

Fingerprint identifies the device first and layers Smart Signals on top — browser bot, VPN, tamper and virtual-machine detection among them (Smart Signals overview). Castle pairs a browser SDK request token with /filter and /risk calls that return scores from 0.0 to 1.0 and an allow, challenge or deny action from your policies (Castle integration guide). Maskbreak returns one verdict per request from POST /v1/evaluate: decision, risk_score, reasons[], a network block and, when the request carries a device event id, a device block with antidetect, automation and, with your accountId, linked_accounts (API reference). This is the category built for the residential-proxy-plus-antidetect stack; what a device layer sees that an IP layer cannot walks through the split. See Fingerprint alternatives and Castle vs Maskbreak.

Comparison table

Cells are what each vendor publishes, linked, as read on 29 August 2026. "Not published" means the pricing page and the docs carried nothing; it does not mean the vendor lacks the capability. "Not read" means the page refused our fetch, so we do not know.

Maskbreak is free during open beta: 1,000 visitor checks an hour per API key, no card, with at least 30 days’ notice before paid changes. This is not a promise of permanent free service. Fingerprint, IPQS and Castle listed free quotas in the dated sources above; check their current terms. Sift, Arkose and Kount published no price in the sources reviewed. The rest of the comparisons section takes these pairs one at a time.

When the other one is right

A per-request verdict says what the network and the device are. It does not decide the order, verify the person, or stand in front of the load balancer. Six cases where another row wins:

• Your loss is chargebacks after payment. Forter approves or declines each transaction at checkout and sells Chargeback Recovery alongside (AWS listing); Sift scores payment abuse as one of its abuse types (Score API docs); Kount quotes on transaction volume (pricing). We return a verdict and a reason list, not an order decision.
• Your question is whether the applicant exists. SEON's enrichment, or IPQS's email and phone validation. We check an email for one thing, a disposable domain, returned as email.disposable.
• Scraping or credential stuffing hits the edge before application code runs. DataDome or Arkose, in front of the app, with a challenge. A verdict API runs at the action; perimeter versus action-level verdicts sets out how the two combine.
• You need native mobile SDKs and an uptime agreement in the contract. Fingerprint's plan table checks iOS and Android native SDKs on every plan, including Pro Plus, and puts a 99.9% uptime agreement on Enterprise only (pricing, re-read 1 September 2026). Ours is a target on the status page, not a contract term.
• You want to write policy in a dashboard rules engine. Castle's policies return allow, challenge or deny from rules you configure (integration guide). Our risk score and decision are fixed unless you add custom rules in the console.
• You will exceed 1,000 requests an hour from one key. That is where our free tier returns 429 (pricing). MaxMind sells by the query with no minimum.

How to test both

A vendor demo shows you the traffic that is easy to catch. Test the traffic that is not. Six sessions, the same six against every candidate, and what a right answer looks like. The first four are four of the network classes that how to evaluate a VPN detection API asks a vendor to tell apart; the two device cases are what this list adds.

The first four separate the network products from each other. The last two separate the products with a device layer from the rest, because an IP-only API returns clean for both, and is right to: it never saw the browser. Run five and six from your own home line so the network block cannot carry the verdict. How residential proxies are detected and Tor exit detection go deeper on cases three and four.

Before you have any of the six, the public sandbox key returns deterministic fixtures for the five network classes, so the parsing and the routing can be written first:

for t in test_clean test_vpn test_proxy test_datacenter test_tor; do
  curl -s -X POST https://maskbreak.com/v1/evaluate \
    -H "Authorization: Bearer sk_test_sandbox" \
    -H "Content-Type: application/json" \
    -d "{\"token\":\"$t\"}" \
  | jq -c "{token: \"$t\", decision, risk_score, reasons, service: .network.service}"
done

{"token":"test_clean","decision":"allow","risk_score":0,"reasons":[],"service":null}
{"token":"test_vpn","decision":"review","risk_score":65,"reasons":["vpn_detected","datacenter_asn"],"service":"PROTON_VPN"}
{"token":"test_proxy","decision":"block","risk_score":80,"reasons":["proxy_detected","datacenter_asn"],"service":"BRIGHT_DATA"}
{"token":"test_datacenter","decision":"allow","risk_score":15,"reasons":["datacenter_asn"],"service":"AWS"}
{"token":"test_tor","decision":"block","risk_score":15,"reasons":["tor_exit_node","anonymous_network"],"service":"TOR"}

Output of the loop, run on 29 August 2026. Each response also carries "test": true and evaluated_in_ms: 1; the 1 is the fixture answering, not a latency measurement. The test_vpn shape matches the suspicious example on the API reference, legacy details.proxied and details.dch mirror included. For latency, time the call at your enforcement point with a real key and take the wall-clock p95, not the vendor's own field.

The shadow-mode protocol

Then run the finalists on live traffic and act on nothing:

1. Call each API on every signup, login or checkout for two weeks. Log decision, risk_score, reasons and the wall-clock time, keyed on your session id. Change no behavior.
2. Join the log to outcomes you already record: chargebacks, disputes, bans, refunds, password resets, support tickets.
3. Count per reason code, not per score band: sessions each code would have blocked, how many later produced an outcome you wanted stopped, and how many known-good customers landed in block.
4. Read the wall-clock p95 at the enforcement point. If the flow cannot carry it, the vendor's own figure does not matter.
5. Enforce block only on codes you reviewed in step three, route review to a step-up, and leave a consumer VPN on review. The fake-signups page shows the routing we run on our own forms.
6. Repeat with the second vendor over the same window and sessions. Two shadow logs on different weeks compare weather, not vendors.

Pricing

The list-price column above is the whole of what nine of the ten publish as of 29 August 2026 (DataDome's page we could not read), each figure linked in its row; contracts differ, and the shapes differ more than the numbers — monthly plans with an overage rate, per-query with no minimum, a flat monthly fee, an annual contract priced by decision volume, and quote-only.

Our limit is hourly, not monthly: a launch that pushes one key past 1,000 requests in a single hour gets 429 for the rest of that hour (pricing), so the free-tier question is about your peak, not your month. Which rows belong on your shortlist depends on the loss; the fake-account software comparison and the free VPN detection API list narrow it for the two most common ones.