# fourzerotwo, free: Phone validation API

> Classify a UK number (mobile, landline, freephone, premium…) and format as E.164.

fourzerotwo's Free key plan for the phone validation API costs $0.00 per 1,000 phones. We check each provider's docs for 9 fields. fourzerotwo's docs list 2: Formats, Type.
You get up to 15,000 calls a month.
We haven't run fourzerotwo through [our phone validation API benchmark](https://datacircle.dev/best-phone-validation-api.txt) yet.
This plan is free. We rank 1,398 plans for phone validation APIs by price. Half the plans cost $3.518 or less per 1,000 phones. [See the best free phone validation API plan.](https://datacircle.dev/best-phone-validation-api.txt)
[GuGuData's CNY 124 (about $19) monthly plan](https://datacircle.dev/validate-phone-apis/gugudata/cny-124-monthly/llms.txt) is the cheapest paid plan per 1,000 phones. GuGuData's CNY 124 (about $19) monthly plan charges nothing per call. You get as many phones as GuGuData's rate limit allows. [Keyronne's pay-as-you-go plan](https://datacircle.dev/validate-phone-apis/keyronne/pay-as-you-go/llms.txt) costs the least for 10,000 phones a month: $0.20.
[Trestle](https://datacircle.dev/validate-phone-apis/trestle/top-up-from-10-self-serve-pay-as-you-go-get-3-0-phone-intel-phone-validation-api/llms.txt), [Signal House](https://datacircle.dev/validate-phone-apis/signal-house/top-up-from-10/llms.txt) and [Data247](https://datacircle.dev/validate-phone-apis/data247/12-pack-membership-get-v3-0-verify247-phone/llms.txt) are the best phone validation API providers in the Datacircle benchmark.

- This page: https://datacircle.dev/validate-phone-apis/fourzerotwo/free
- [Phone validation API in 2026: the best of 60+ compared](https://datacircle.dev/best-phone-validation-api.txt)
- Get it: https://fourzerotwo.si/free?utm_source=datacircle.dev&utm_medium=referral&utm_campaign=phone-validation-api-pricing
- Request: `GET https://fourzerotwo.si/v1/validators/uk-phone`
- API key: with the plan, on https://fourzerotwo.si/free?utm_source=datacircle.dev&utm_medium=referral&utm_campaign=phone-validation-api-pricing
- Its API docs: https://fourzerotwo.si/apis/validators/uk-phone?utm_source=datacircle.dev&utm_medium=referral&utm_campaign=phone-validation-api-pricing
- Sold by: fourzerotwo (https://fourzerotwo.si?utm_source=datacircle.dev&utm_medium=referral&utm_campaign=phone-validation-api-pricing)
- Checked: 2026-11-10

## In the answer

- Completeness: 22%
- Formats: ✓
- Type: ✓

## Price

- $ per 1,000 phones: $0.00
- Per: call
- Billing: free

## Aggregators

- Aggregators: none

## Charges

- Also pays for: from the same budget: 529 other fourzerotwo calls: 500 a day

## Not found

- $ per 1,000 calls that find nothing: $0.00

## In their words

- Their pitch: Classify a UK number (mobile, landline, freephone, premium…) and format as E.164.

## Data

- Countries: United Kingdom
- What it checks: numbering plan
- Keep data: no API terms
- Use data: Keep the attribution when you show the data.

## Plan

- Pay: $0
- Enough for: 15,000 calls a month

## Rate limit

- Per day: 500
- Batch: 1

## Speed

- Answer: in the call

## The call

- You send: number
- Method: GET
- Path: /v1/validators/uk-phone

## About the plan

- Plan: Free key
- Who can get it: anyone with an email address

## The 2 fields the plan's answer can hold

line type, E.164 format

## fourzerotwo's plans (5)

- [fourzerotwo, free](https://datacircle.dev/validate-phone-apis/fourzerotwo/free/llms.txt): $0.00 per 1,000, 22% complete
- [fourzerotwo, pay as you go](https://datacircle.dev/validate-phone-apis/fourzerotwo/pay-as-you-go/llms.txt): $0.50 per 1,000, 22% complete
- [fourzerotwo, $5 pack](https://datacircle.dev/validate-phone-apis/fourzerotwo/5-pack/llms.txt): $0.50 per 1,000, 22% complete
- [fourzerotwo, $20 pack](https://datacircle.dev/validate-phone-apis/fourzerotwo/20-pack/llms.txt): $0.50 per 1,000, 22% complete
- [fourzerotwo, $50 pack](https://datacircle.dev/validate-phone-apis/fourzerotwo/50-pack/llms.txt): $0.50 per 1,000, 22% complete

## fourzerotwo's calls for this API (1)

- `GET /v1/validators/uk-phone`: [fourzerotwo, free](https://datacircle.dev/validate-phone-apis/fourzerotwo/free/llms.txt)

## fourzerotwo's APIs (8)

- [fourzerotwo: business verification API pricing, 5 plans](https://datacircle.dev/business-verification-apis/fourzerotwo/free/llms.txt)
- [fourzerotwo: company discovery API pricing, 5 plans](https://datacircle.dev/company-discovery-apis/fourzerotwo/free/llms.txt)
- [fourzerotwo: company enrichment API pricing, 5 plans](https://datacircle.dev/company-enrichment-apis/fourzerotwo/free/llms.txt)
- [fourzerotwo: domain WHOIS API pricing, 5 plans](https://datacircle.dev/domain-whois-apis/fourzerotwo/free/llms.txt)
- [fourzerotwo: email verification API pricing, 5 plans](https://datacircle.dev/validate-email-apis/fourzerotwo/free/llms.txt)
- [fourzerotwo: phone validation API pricing, 5 plans](https://datacircle.dev/validate-phone-apis/fourzerotwo/free/llms.txt)
- [fourzerotwo: web scraping API pricing, 5 plans](https://datacircle.dev/web-scraping-apis/fourzerotwo/free/llms.txt)
- [fourzerotwo: IP company lookup API pricing, 5 plans, GET /v1/ip-geolocation/batch](https://datacircle.dev/ip-company-lookup-apis/fourzerotwo/free-key-get-v1-ip-geolocation-batch/llms.txt)
- [fourzerotwo: IP company lookup API pricing, 5 plans, GET /v1/ip-geolocation/lookup](https://datacircle.dev/ip-company-lookup-apis/fourzerotwo/free-key-get-v1-ip-geolocation-lookup/llms.txt)
- [fourzerotwo: IP company lookup API pricing, 5 plans, GET /v1/domains/ip-owner](https://datacircle.dev/ip-company-lookup-apis/fourzerotwo/free-key-get-v1-domains-ip-owner/llms.txt)
- [fourzerotwo: IP company lookup API pricing, 5 plans, GET /v1/ip-geolocation/asn](https://datacircle.dev/ip-company-lookup-apis/fourzerotwo/free-key-get-v1-ip-geolocation-asn/llms.txt)

## fourzerotwo: phone validation API alternatives

- [ReefAPI, $450 quarterly, Enterprise quarterly, POST /phone-validate/v1/validate](https://datacircle.dev/validate-phone-apis/reefapi/450-quarterly-enterprise-quarterly-post-phone-validate-v1-validate/llms.txt): $0.50 per 1,000, 67% complete, stored
- [APIFreaks, $20 pack, One-Off 80,000 credits, POST /phone/validation/bulk](https://datacircle.dev/validate-phone-apis/apifreaks/20-pack-one-off-80000-credits-post-phone-validation-bulk/llms.txt): $0.50 per 1,000, 67% complete, stored
- [Temsor, $10 pack](https://datacircle.dev/validate-phone-apis/temsor/10-pack/llms.txt): $0.50 per 1,000, 44% complete
- [The Blacklist Alliance, $3,500 monthly](https://datacircle.dev/validate-phone-apis/the-blacklist-alliance/3500-monthly/llms.txt): $0.50 per 1,000, 44% complete

## Sources

From each provider's own pricing page and docs, and from what providers tell us. We read this row from these pages on 2026-11-10.

- https://fourzerotwo.si/apis/validators/uk-phone?utm_source=datacircle.dev&utm_medium=referral&utm_campaign=phone-validation-api-pricing
- https://fourzerotwo.si/catalog.json?utm_source=datacircle.dev&utm_medium=referral&utm_campaign=phone-validation-api-pricing
- https://fourzerotwo.si/credits?utm_source=datacircle.dev&utm_medium=referral&utm_campaign=phone-validation-api-pricing
- https://fourzerotwo.si/free?utm_source=datacircle.dev&utm_medium=referral&utm_campaign=phone-validation-api-pricing
- https://fourzerotwo.si/llms.txt?utm_source=datacircle.dev&utm_medium=referral&utm_campaign=phone-validation-api-pricing
- https://fourzerotwo.si/openapi.json?utm_source=datacircle.dev&utm_medium=referral&utm_campaign=phone-validation-api-pricing