Phone Number Checker API — Bulk Verification Examples

The Phone Number Checker API is a bulk, asynchronous, file-based API used to validate phone numbers and evaluate activity-related signals. Upload an input file, poll the returned task ID, then download the exported results. This repository contains runnable examples in Python, Node.js, Go, Java, C#, PHP, browser JavaScript, and Shell.

• Base URL: https://api.checknumber.ai
• Auth: X-API-Key request header
• Full API docs: https://docs.checknumber.ai/phone-number-validation
• Get an API key: https://platform.checknumber.ai

Note

This is a bulk, file-based, asynchronous API. It does not perform a single real-time lookup in one request/response cycle.

Table of Contents

• How do I validate phone numbers via API?
• How do I process Phone checks in bulk?
• What request parameters does the API take?
• What does the task response look like?
• How do I check whether a phone number is active?
• How do I detect high-value phone users via API?
• What does the Phone number checker API cost?
• Phone number checker API vs alternatives
• Code examples
• Status codes
• FAQ
• Support & legal

How do I validate phone numbers via API?

Send a POST request to https://api.checknumber.ai/v1/tasks with the API key, numbers.txt, and task_type=phoneCheck. The response contains a task_id used to retrieve task status and the final result_url.

curl --location 'https://api.checknumber.ai/v1/tasks' \
  --header 'X-API-Key: YOUR_API_KEY' \
  --form 'file=@"./numbers.txt"' \
  --form 'task_type="phoneCheck"'

Each line in numbers.txt is one phone number in E.164 format, such as +14155552671.

How do I process Phone checks in bulk?

1. Submit the input file to POST /v1/tasks.
2. Poll POST /v1/gettasks with the returned task_id while status moves from pending to processing.
3. Download the file at result_url when status becomes exported.

curl --location 'https://api.checknumber.ai/v1/gettasks' \
  --header 'X-API-Key: YOUR_API_KEY' \
  --form 'task_id="YOUR_TASK_ID"'

See examples/ for complete submit → poll → download implementations.

What request parameters does the API take?

Submit task — POST /v1/tasks

Parameter	Type	Description
file	file	Text file containing one E.164 phone number per line for the main task type. Email variants use emails.txt.
task_type	string	One of: phoneCheck, active_check, high_value_users.

Check status — POST /v1/gettasks

Parameter	Type	Description
task_id	string	Task ID returned by task creation.

Main task result fields — task_type=phoneCheck

Field	Description
Number	Phone number in E.164 format
phoneCheck	Validation outcome / detail (per exported column headers)

What does the task response look like?

{
  "created_at": "2026-07-13T08:24:56Z",
  "updated_at": "2026-07-13T08:25:43Z",
  "task_id": "example-task-id",
  "user_id": "example-user-id",
  "status": "exported",
  "total": 1000,
  "success": 998,
  "failure": 2,
  "result_url": "https://example.invalid/results.xlsx"
}

All variants use this task envelope. Only task_type, input content, and exported result columns vary.

How do I check whether a phone number is active?

Classifies the documented activity status for each number. Use task_type=active_check; the submit, poll, and download workflow is otherwise unchanged.

curl --location 'https://api.checknumber.ai/v1/tasks' \
  --header 'X-API-Key: YOUR_API_KEY' \
  --form 'file=@"./numbers.txt"' \
  --form 'task_type="active_check"'

Input: one phone number per line in E.164 format (for example, +14155552671).

Result fields (copied from the canonical documentation):

Field	Description
Number	Phone number in E.164 format
ActiveStatus	Activity level of the number: active, inactive, or unknown

How do I detect high-value phone users via API?

Returns the documented high-value-user detection result. Use task_type=high_value_users; the submit, poll, and download workflow is otherwise unchanged.

curl --location 'https://api.checknumber.ai/v1/tasks' \
  --header 'X-API-Key: YOUR_API_KEY' \
  --form 'file=@"./numbers.txt"' \
  --form 'task_type="high_value_users"'

Input: one phone number per line in E.164 format (for example, +14155552671).

Result fields (copied from the canonical documentation):

Field	Description
Number	Phone number
Result	High-value user detection result (yes / no style; labels per export)

What does the Phone number checker API cost?

Rates vary by task type and are billed against the account balance. See the current terms at https://checknumber.ai/pricing and query the remaining balance with GET https://api.checknumber.ai/v1/balance.

Phone number checker API vs alternatives

Capability	CheckNumber API	Generic carrier lookup	Manual checking
Checks the documented Phone signal	Yes	No	May be possible
Bulk file upload	Yes	Varies	No
Asynchronous processing	Yes	Varies	No
Downloadable structured results	Yes	Varies	No

This compares general approaches, not named vendors. Capabilities vary by provider and account access.

Code examples

Language	Example
Python	examples/python
Node.js	examples/nodejs
Go	examples/go
Java	examples/java
C#	examples/csharp
PHP	examples/php
JavaScript (browser)	examples/javascript
Shell (curl)	examples/shell

Set the API key before running a server-side example:

export CHECKNUMBER_API_KEY="YOUR_API_KEY"

Status codes

Status	Billing	Description
200	charge	Request successful; task created or status retrieved.
400	free	Invalid parameters or file format.
500	free	Internal server error; retry later.

FAQ

Is this a single-number real-time lookup?
No. Submit a file, poll for completion, and download the result file.

Which task types are available in this repository?

• task_type=phoneCheck — Phone Number Validation; Returns the documented phone validation outcome for each E.164 number. Input: numbers.txt.
• task_type=active_check — Phone Number Activity Check; Classifies the documented activity status for each number. Input: numbers.txt.
• task_type=high_value_users — High-Value User Checker; Returns the documented high-value-user detection result. Input: numbers.txt.

Which input format should I use?
Phone-based checks require one E.164 number per line. Email variants require one email address per line.

How do I check my balance?
Call GET https://api.checknumber.ai/v1/balance with the X-API-Key header.

Support & legal

• Documentation: https://docs.checknumber.ai/phone-number-validation
• Dashboard and API keys: https://platform.checknumber.ai
• License: MIT for the sample code

Process only data you are authorized to use and comply with applicable privacy laws and platform terms. CheckNumber is not affiliated with or endorsed by Phone.

---

Last updated: 2026-07-13 · Maintained by CheckNumber. Canonical docs: https://docs.checknumber.ai/phone-number-validation