Best VoIP Detection API for KYC: 8 APIs Compared

Quick answer: To separate non-fixed VoIP (Google Voice-style) from fixed VoIP at sign-up, use Twilio Lookup’s Line Type Intelligence: of the seven value lists we could read, only it returns both (fixedVoip, nonFixedVoip), at $0.008 per request as at 20 October 2026. Telesign Phone ID flags non-fixed VoIP and prepaid. The other five return one undivided VoIP value. Treat the result as a step-up trigger, not a verdict.

This page compares eight phone-intelligence APIs a fintech or KYC team might use to screen the number an applicant types into a sign-up form: Twilio Lookup v2, Telesign Phone ID, Vonage Identity Insights (which replaces Vonage Number Insight), Telnyx Number Lookup, Prove, IPQualityScore (IPQS) Phone Validation, Plivo Lookup and Sinch Number Lookup v2. Every value below is copied from each vendor’s own API reference or OpenAPI schema, read on 20 October 2026. Two caveats come first: zian.ai publishes this comparison, and Zian does not sell a lookup API, so it is not in the vendor table. Nothing here is legal advice. A line-type check is a fraud signal, not identity verification: it tells you what kind of number was entered, not who holds it.

Where an AI onboarding agent like Zian fits after the lookup

A VoIP detection API decides which path an applicant takes, but it does not complete that path. The step-up branch is where applicants drop out, and an AI onboarding agent can run the conversations that branch creates while the verification decision stays with your compliance team. Zian lists a niched agent called Bank Registration Onboarding (KYC). Zian’s published capabilities include outbound voice calls, SMS, email and WhatsApp follow-up, answering inbound calls 24/7, and research and knowledge-base lookups, which is the kind of work a step-up queue generates.

The lookup and the decision belong in your own rules engine and your compliance team’s policy. The agent connects to the systems around it through Zian’s API and CRM integrations (HubSpot, Salesforce, HighLevel, Zapier), and Zian supports private model deployment on your own infrastructure, which matters when applicant data must not leave the bank. Zian is in a partnership-application beta. The pattern behind this split, a conversational layer in front of compliance and never in place of it, is set out in our guide to AI onboarding agents for bank KYC and account setup.

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The line-type values each VoIP detection API actually returns

The table below is the main reference on this page. The “Exact values” column copies each vendor’s enum or value list as printed in its own reference, spelling and case included, because your code will match on these strings. Field names come from the same pages.

API (read 20 Oct 2026)	Field	Exact values the reference lists	Separate fixed and non-fixed VoIP values?	Flags non-fixed VoIP specifically?	Carrier name field
Twilio Lookup v2, Line Type Intelligence	line_type_intelligence.type	landline, mobile, fixedVoip, nonFixedVoip, personal, tollFree, premium, sharedCost, uan, voicemail, pager, unknown (12)	Yes	Yes (nonFixedVoip)	carrier_name
Telesign Phone ID	phone_type.code / phone_type.description	FIXED_LINE, MOBILE, PREPAID, TOLL_FREE, VOIP, PAGER, PAYPHONE, INVALID, RESTRICTED_PREMIUM, PERSONAL, VOICEMAIL, OTHER (12)	No: traceable fixed VoIP is counted inside FIXED_LINE	Yes: Telesign defines VOIP as “non-fixed VOIP”	carrier.name
Vonage Identity Insights	original_carrier.network_type	MOBILE, LANDLINE, TOLLFREE, PREMIUM, VIRTUAL (5; Vonage says the enum “is extensible”)	No	No	original_carrier.name, current_carrier.name
Telnyx Number Lookup	carrier.type	fixed line, mobile, voip, fixed line or mobile, toll free, premium rate, shared cost, personal number, pager, uan, voicemail, unknown (12)	No	No	carrier.name, normalized_carrier
IPQS Phone Validation	line_type, plus VOIP and prepaid booleans	Toll-Free, Wireless, Landline, Satellite, VOIP, Premium Rate, Pager, N/A (8)	No	No	carrier
Plivo Lookup	carrier.type	fixed, mobile, voip, toll-free, unknown (5)	No	No	carrier.name
Sinch Number Lookup v2	line.type, plus voIPDetection.probability	Landline, Mobile, VoIP, Special, Freephone, Other (6); probability Unknown, Low, Likely, High (VoIP detection is labelled alpha)	No	No	line.carrier
Prove (archived copies, see below)	lineType; Global Fraud Policy reason codes	Full lineType list not read (the reference example shows mobile). Reason code 9134: “The phone isn’t trusted because it’s a non-fixed VoIP number.”	Not read	Yes, as a policy failure reason (9134)	carrier (in the identity lookup example)

One notable inconsistency: IPQS lists Toll-Free in its value list, but its own sample response prints "Toll Free" without the hyphen. If your rule matches toll-free numbers by exact string, match both spellings. Vonage’s older Number Insight API used lower-case values (mobile, landline, landline_premium, landline_tollfree, virtual, unknown, pager, null). Vonage’s overview page says Number Insight will be sunset on 4 February 2027, so new builds should target Identity Insights.

Why non-fixed VoIP is the line type KYC teams care about

A non-fixed VoIP number is a virtual number someone can obtain online without a physical line or device. Twilio’s reference gives Google Voice and Enflick as examples. A fixed VoIP number is tied to a physical service, and Twilio’s examples are Comcast and Vonage. For a sign-up screen the difference matters because of who can obtain each kind of number, and from where.

Telesign gives the clearest reasoning in its own phone-type table. It says non-fixed VoIP numbers “can easily be obtained by users who are not located in the country associated with the telephone number”, that “they are untraceable and disposable; some can even be obtained for free”, and it assigns them a High risk level with the recommended action Block. Telesign rates traceable fixed VoIP differently. It counts those numbers inside FIXED_LINE, gives them a Low risk level and recommends Allow.

This is why the “Separate fixed and non-fixed VoIP values?” column matters. An API that returns a single voip value puts a cable-company home phone and a free app number in the same bucket. A rule that blocks voip on such an API will block both. A rule that allows voip will allow both.

The counter-argument also needs stating. NIST’s current authentication guideline no longer forbids VoIP numbers for out-of-band authentication, although the same revision still calls use of the phone network for out-of-band verification “restricted”, and it is authentication guidance rather than a rule for screening sign-up numbers. The change log of SP 800-63B Revision 4 says Section 3.1.3.1 “removes the prohibition on the use of VoIP phone numbers for out-of-band authentication”. Telesign’s own table also warns that “not all prepaid mobile phones will be identified as prepaid; some will be identified as Mobile.” A line type is a probability signal. Many legitimate applicants use VoIP numbers, and a blanket block will turn some of them away.

The line-type crosswalk: returned value to KYC action

This is our decision table for a consumer sign-up flow. It maps each vendor’s exact values onto three actions. It is a method you can adapt, not a regulatory rule, and the right threshold depends on the product: a savings account and a crypto exchange will set it differently. The “vendor guidance” column quotes Telesign because its reference attaches a recommended action to every phone type. We did not find an equivalent per-type table in the pages we read for the other seven.

What the lookup returned	Exact values across the eight APIs	Suggested action	Vendor guidance on its own page
Mobile	mobile (Twilio, Telnyx, Plivo), MOBILE (Telesign, Vonage), Mobile (Sinch), Wireless (IPQS)	Allow; continue standard verification (for example, a one-time code)	Telesign: Medium-Low, Allow
Prepaid mobile	PREPAID (Telesign), prepaid: true (IPQS), contract_type: PREPAID (Vonage subscriber tenure insight, labelled Alpha)	Step-up verification	Telesign: Medium-High, Flag
Landline or fixed line	landline (Twilio), FIXED_LINE (Telesign), LANDLINE (Vonage), fixed line (Telnyx), Landline (IPQS, Sinch), fixed (Plivo)	Allow, but deliver codes by voice: Twilio notes landlines “generally can’t receive SMS messages”	Telesign: Low, Allow
Fixed VoIP	fixedVoip (Twilio only)	Allow; voice or SMS code depending on what the line accepts	Telesign counts it under FIXED_LINE: Allow
Non-fixed VoIP	nonFixedVoip (Twilio), VOIP (Telesign), reason code 9134 (Prove)	Step-up verification; block only if a second signal agrees	Telesign: High, Block
VoIP, type unspecified	voip (Telnyx, Plivo), VoIP (Sinch), VOIP line type or VOIP: true (IPQS), VIRTUAL (Vonage)	Step-up verification, and resolve with a second signal (Sinch voIPDetection.probability, IPQS fraud_score)	None that splits it
Toll-free, premium, shared cost, pager, payphone, voicemail, UAN	tollFree, premium, sharedCost, pager, voicemail, uan (Twilio); TOLL_FREE, RESTRICTED_PREMIUM, PAGER, PAYPHONE, VOICEMAIL (Telesign); equivalents at the others	Block as a personal contact number; ask for another number	Telesign: High or Medium-High, Block
Personal number	personal (Twilio), PERSONAL (Telesign), personal number (Telnyx)	Allow; check where it forwards if your process needs possession	Telesign: Medium-Low, Allow
Unknown or invalid	unknown, INVALID, OTHER, N/A, Other	Ask the applicant to re-enter; block INVALID	Telesign: INVALID and OTHER, Block
Recent SIM swap or recent port	Separate signals (see the next section)	Hold and step up before any account change	Prove: reason codes for SIM swap and port “under 24 hours”

In short, our crosswalk allows mobile, landline, fixed VoIP and personal numbers. It blocks numbers that cannot serve as an individual’s contact number (toll-free, premium, pager, payphone, voicemail) and invalid numbers. It sends non-fixed VoIP, unspecified VoIP and prepaid results to step-up verification, asks for re-entry when the type is unknown, and holds any account change after a recent SIM swap or port. An automatic block on a VoIP result is reserved for cases where a second signal agrees with the first.

Two choices in this table go against parts of the vendors’ own guidance, and you should know which ones. We suggest step-up for non-fixed VoIP where Telesign recommends Block, because of the NIST change above and because a blocked legitimate applicant costs you a customer. IPQS makes a similar point in its response-parameters page: it recommends blocking on a combination of signals and says “you may find better results validating phone numbers by only blocking invalid and recent_abuse phone numbers or Fraud Scores greater than 85-90+.”

What a line-type lookup does not tell you: porting, SIM swap and reassignment

The line type describes the kind of number. It says nothing about who holds the number today, or whether that changed yesterday. Those questions are answered by separate signals, and the eight vendors package them differently.

API	Porting signal in the lookup response	SIM swap	Other risk fields worth knowing
Twilio Lookup v2	No ported field among the five Line Type Intelligence properties	Separate sim_swap package; Twilio says it “requires carrier registration and approval”, bills per request even when no data comes back, and is in Beta	Line Status, Reassigned Number, Call Forwarding, SMS Pumping Risk and Identity Match are separate packages; Line Type Override lets you correct a type you know is wrong
Telesign Phone ID	porting_status, an add-on Telesign must enable for your account	sim_swap add-on	number_deactivation and subscriber_status add-ons; phone-type override reason codes
Vonage Identity Insights	No ported flag; you compare original_carrier (Vonage: “based on the numbering plan prefix”) with current_carrier (mobile numbers only)	sim_swap insight, priced per country	Subscriber Match, device swap, roaming and reachability insights; subscriber tenure (returns contract_type PREPAID, CONTRACT or BUSINESS), number recycling and scam signal insights, which Vonage labels Alpha
Telnyx Number Lookup	portability.ported_status (Y, N or empty) and ported_date	Not part of the Number Lookup schema	The response’s fraud field is documented as “Unused”
IPQS Phone Validation	ported and last_ported_date	Not in the phone validation response parameters	recently_recycled, recent_abuse, fraud_score (0–100), leaked, risky
Plivo Lookup	carrier.ported: yes, no or unknown, US and Canada only	Not in the Lookup API document	Separate CNAM lookup for US numbers
Sinch Number Lookup v2	line.ported and line.portingDate	Separate SimSwap feature in the same request, with swap periods from SP4H to SP30D, plus SPMAX and Undefined	RND (disconnected-number check, alpha)
Prove	Reason code 9136: “Potential ATO due to recent Port under 24 hours”	Reason code 9135: “recent SIM Swap under 24 hours”	Reason codes for call forwarding (9137), recycled numbers and short-tenure numbers

Treat “ported numbers are a separate product” with care. Five of the eight return a porting signal in the same response (Telnyx, IPQS, Plivo for US and Canada, Sinch, and Telesign as an add-on), and Prove reflects recent ports in its fraud-policy result. SIM swap is consistently separate: it is its own request, add-on or feature at every vendor that documents it, and often needs carrier approval. NIST asks verifiers to consider this kind of signal. Section 3.1.3.3 of SP 800-63B says verifiers “SHOULD consider risk indicators (e.g., device swap, SIM change, number porting, other abnormal behavior) before using the PSTN to deliver an out-of-band authentication secret.”

If your onboarding flow ends with a phone call rather than a code, the same reasoning applies to the call. Our guide to verifying caller identity on AI phone agents covers what a number can and cannot prove once someone is on the line.

What a VoIP detection API costs per lookup

We printed a price only where the vendor’s own page shows one, read on 20 October 2026. The worked figure assumes 10,000 sign-up lookups a month at the published rate, before volume discounts.

API	Published price for the line-type lookup	10,000 lookups	Notes
Twilio Line Type Intelligence	$0.008 per request	$80	Basic formatting and validation is free; SIM swap is priced through sales
Telesign Phone ID	0.011 per transaction (the same figure for all 233 countries in Telesign’s pricing data)	110	The pricing data we read printed no currency symbol; additional attributes (porting, SIM swap) are “Talk to sales”
Vonage Identity Insights	Original Carrier €0.001 / $0.00117; Current Carrier €0.007 / $0.00819 per request	$11.70 (Original only); $93.60 (both)	Archived copy of Vonage’s pricing page, captured 16 October 2026 (the live page returned 403 to us). SIM Swap: “Price varies per country”
Telnyx Number Lookup	“from $0.0015 per query”	from $15	The rate card lists LRN $0.0015, MCC/MNC $0.0025 and CNAM $0.003 per query. We could not confirm which line a carrier lookup bills under, so the worked figure uses Telnyx’s own “from” rate
Plivo Lookup	USD 0.004 per request	$40	Stated in Plivo’s Lookup API document
IPQS Phone Validation	Credit plans, not a per-lookup price: Free plan 1,000 credits; Startup plan 5,000 credits at $139.99 a month	Plan-dependent	We did not find a per-lookup credit cost in IPQS’s documentation; the plans page offers “1,000 Free Lookups!” next to the Free plan’s 1,000 credits
Sinch Number Lookup v2	We could not find a published price	n/a	Checked sinch.com/pricing/, the Number Lookup product page and Sinch’s page sitemap
Prove	We could not find a published price	n/a	prove.com/pricing returned 404; no pricing URL in Prove’s 1,585-URL sitemap

Read the price column against the values table, not on its own. At the published rates, the cheapest per-request figure belongs to Vonage’s Original Carrier insight at $0.00117. Vonage describes that insight as based on the numbering plan prefix, so it shows the type of the range a number was issued from and will not reflect a number that has since been ported. Twilio costs more per request, but it was the only one of the seven value lists we read that separates fixed from non-fixed VoIP. Twilio’s own pricing FAQ suggests a cheaper pattern: “use free validation on every signup, add line type only where channel eligibility matters, reserve SIM swap or identity checks for higher-risk flows.”

How to choose the best VoIP detection API for KYC

There is no single winner, because the eight do different jobs. Choose by which question your rule has to answer.

• You need to separate fixed from non-fixed VoIP: Twilio Lookup v2 Line Type Intelligence. Twilio says it is available for numbers worldwide, but Canadian numbers need special approval for NPAC data, and a query without that access returns error 60601.
• You want a vendor-stated risk level and action for every type: Telesign Phone ID. Its phone-type table assigns Low to High risk and Allow, Flag or Block to all twelve codes, and it flags prepaid separately. Remember that its VOIP means non-fixed only.
• You want line type plus a fraud score and recycled-number flag in one call: IPQS Phone Validation. Its single VOIP value does not separate fixed from non-fixed.
• You want porting data from the network in the same response, at a low published rate: Telnyx Number Lookup (ported_status, ported_date, LRN) or Plivo Lookup (ported flag for US and Canada only).
• You want SIM swap reported in set windows (4 hours to 30 days) alongside line type: Sinch Number Lookup v2. Its VoIP probability score is labelled alpha. Sinch is not the only way to get both in one call: Twilio Lookup v2 accepts several fields in one request (for example line_type_intelligence,sim_swap), Vonage Identity Insights takes several insights in one request, and Telesign Phone ID returns SIM swap as an add-on, each subject to that vendor’s approval steps.
• You are building on Vonage: plan for Identity Insights, because Number Insight is being sunset on 4 February 2027.
• You want a pass or fail identity decision rather than raw line types: Prove. Its Global Fraud Policy returns failure reasons, including non-fixed VoIP (9134), instead of leaving the decision to your rules engine. Its identification reason codes reference US data such as SSN, so check coverage for your market.

Methodology: how we read each VoIP detection API

We defined every term before filling any cell, and applied each definition the same way to all eight rows.

• Exact values: the enum or value list printed in the vendor’s own API reference or OpenAPI schema. Examples alone do not count, except for Prove, where we say the full list was not read.
• Separate fixed and non-fixed VoIP values: Yes only if the reference lists two distinct values, one for each.
• Flags non-fixed VoIP specifically: Yes if a value, or a documented reason code, is defined as non-fixed VoIP. A generic “VoIP” value scores No.
• Carrier name field: a documented response field that returns a carrier or operator name.
• Published price: a figure on the vendor’s own pricing page or documentation. Where we found none, the cell names the pages we checked.
• Archived sources: from our location developer.prove.com redirected to a sign-in and security checkpoint, and vonage.com returned 403. For those pages we used dated Wayback Machine captures (Prove’s Global Fraud Policy captured 16 May 2026; Prove’s identity lookup reference captured 12 March 2026; Vonage’s pricing page captured 16 October 2026). Vonage’s API schemas came live from developer.vonage.com. A blocked site is not scored down.

This is a sample of eight APIs, not a sweep of every phone-intelligence vendor. If you store lookup results against an applicant record, they become part of your privacy footprint. See our explainer on whether a phone number in a log is personal information before you decide how long to keep them.

Running the step-up branch without losing the applicant

Every “step-up” cell in the crosswalk creates work. The applicant has to be told why, asked for something else, and chased if they stall. Even a small share of sign-ups routed to step-up creates a queue, and a queue nobody works turns into abandoned applications. Decide who works it before the rule goes live.

For Australian reporting entities, the timing of that queue interacts with the AML/CTF rules on when verification must be complete. Our walkthrough of delayed verification and what an AI KYC agent may do under AUSTRAC rules covers which steps can happen before verification finishes and which cannot. An AI onboarding agent can handle the first contact and the follow-up on that queue across voice, SMS, email and WhatsApp, while the verification decision stays with your compliance process.

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Frequently asked questions

Where every figure on this page comes from

Figure	Who published it	Link	Date read
Line Type Intelligence: 12 type values incl. fixedVoip, nonFixedVoip; Google Voice, Enflick, Comcast, Vonage examples; Canada approval and error 60601	Twilio	twilio.com/docs/lookup/v2-api/line-type-intelligence	20 Oct 2026
Line Type Intelligence $0.008 per request; free basic validation; “use free validation on every signup…” quote	Twilio	twilio.com Lookup pricing	20 Oct 2026
SIM Swap: carrier registration and approval, Beta, billed per request	Twilio	twilio.com/docs/lookup/v2-api/sim-swap	20 Oct 2026
Line Type Override for incomplete or inaccurate responses	Twilio	twilio.com/docs/lookup/v2-api/line-type-override	20 Oct 2026
12 phone type codes, risk levels, Allow/Flag/Block actions, non-fixed VoIP and prepaid wording	Telesign	developer.telesign.com codes page	20 Oct 2026
porting_status, sim_swap, number_deactivation add-ons	Telesign	developer.telesign.com Phone ID reference	20 Oct 2026
Phone ID 0.011 per transaction; 233 countries; additional attributes “Talk to sales”	Telesign	telesign.com/pricing/identity-pricing (figures from the page’s pricing data file)	20 Oct 2026
Number Insight sunset 4 February 2027	Vonage	developer.vonage.com Number Insight overview	20 Oct 2026
Identity Insights network_type values; “based on the numbering plan prefix”; SIM swap, Subscriber Match and other insights	Vonage	developer.vonage.com Identity Insights API reference	20 Oct 2026
Number Insight network_type values and ported values	Vonage	developer.vonage.com Number Insight API reference	20 Oct 2026
Original Carrier €0.001 / $0.00117; Current Carrier €0.007 / $0.00819; SIM Swap price varies per country	Vonage (archived copy, captured 16 Oct 2026)	web.archive.org capture of Vonage pricing	20 Oct 2026
Number Lookup carrier.type 12 values; ported_status; fraud “Unused”	Telnyx	developers.telnyx.com Number Lookup reference	20 Oct 2026
From $0.0015 per query; LRN $0.0015, MCC/MNC $0.0025, CNAM $0.003	Telnyx	telnyx.com/pricing/number-lookup	20 Oct 2026
line_type 8 values; VOIP, prepaid, ported, recently_recycled; fraud score 85+/90+ guidance quote	IPQualityScore	ipqualityscore.com response parameters	20 Oct 2026
Free plan 1,000 credits; Startup 5,000 credits at $139.99 a month	IPQualityScore	ipqualityscore.com/plans	20 Oct 2026
carrier.type 5 values; ported US/Canada only; USD 0.004 per request	Plivo	plivo.com/docs/lookup/overview	20 Oct 2026
line.type 6 values; VoIP probability 4 values (alpha); SIM swap periods; RND	Sinch	developers.sinch.com Number Lookup v2 reference	20 Oct 2026
Reason codes 9134, 9135, 9136, 9137	Prove (archived copy, captured 16 May 2026)	web.archive.org capture of Prove Global Fraud Policy	20 Oct 2026
lineType example mobile; carrier field	Prove (archived copy, captured 12 Mar 2026)	web.archive.org capture of Prove identity lookup	20 Oct 2026
Rev. 4 removes VoIP prohibition (Sec. 3.1.3.1); risk indicators before PSTN use (Sec. 3.1.3.3)	NIST	pages.nist.gov SP 800-63B	20 Oct 2026
10,000-lookup costs ($80, 110, $11.70, $93.60, from $15, $40)	zian.ai, derived from the published rates above	This page	20 Oct 2026