Check if a phone number has an X (Twitter) account

The X check indicates whether an account on X, the platform formerly called Twitter, is associated with a phone number. It answers registered: true, false or null (unknown) with the time of the check. It runs in real time and in bulk jobs, for numbers from any country, and returns no handle, name, photo or post.

How do I check if a number is linked to an X account?

Send the number to the API with the check x (or its alias twitter). The answer is registered: true when an X account is associated with the number, false when none is, and null when no conclusive answer was available, which is free. It works in real time for one number at a time and in bulk jobs for lists, and it never contacts the number or the account.

Inside the X app, the only number-based feature is contact discovery: people who allow it can be suggested to others who uploaded their number in an address book, and anyone can turn that off (X Help Center: email and phone discoverability). Our check is not a way around that setting. It doesn't reveal which account it is, only whether one exists.

What does the X check tell you?

It tells you whether the phone number is linked to an X account. On X the phone number is optional. People can register with an e-mail address and add a number later to sign in, recover the account or pass a security check. A true answer means an account is associated with the number now.

• registered: true: an X account is associated with the number.
• registered: false: a conclusive "no".
• registered: null: no conclusive answer (status, reason). You are not charged.

Two platform changes affect how you should read the answer. Twitter was renamed X in July 2023. Aliases x and twitter therefore both work, and older integrations that send twitter keep running. And since 20 March 2023, text-message two-factor authentication has been available only to paying subscribers (Twitter announcement, February 2023). The same announcement notes that turning off text-message 2FA doesn't remove the number from the account. One number can also be associated with up to 10 X accounts (X Help Center). Fewer people have a reason to attach a number than before, so a false answer is common and fairly neutral.

Who uses it, and why?

Teams use the X check as a supporting signal for account security and sign-up quality, usually in a multi-check with other platforms.

• Account-security reviews. When a user changes the phone number on their account with you, a number with some history on large platforms is a mildly reassuring sign. A number with no footprint anywhere may deserve a second look. See account security.
• Sign-up protection. Together with Instagram, Facebook and a carrier lookup, it helps separate numbers people actually use from numbers set up for a single sign-up.
• Data hygiene. Along with other checks, it helps you judge whether old contact numbers you are allowed to process are still in use.

If you collect e-mail addresses rather than numbers, the X e-mail check answers the same question for an address. It runs in bulk jobs only.

What do you get back?

Each number gets one result under checks["x.registered"], with no extra attributes.

How is it billed?

You pay per number checked, and only for conclusive answers. You're not charged for inconclusive results (unknown, unsupported country, timeout, invalid, duplicate). Real-time and bulk checks are priced separately. See pricing. Cache hits inside the freshness window are free, and max_age: 0 forces a fresh, billed check.

What are the limits?

The X check runs in real time (POST /v1/lookup, up to 100 identifiers) and in bulk jobs (POST /v1/jobs, up to 50,000 per job), for numbers from every country.

• A request can hold up to 20 checks. Numbers × checks is capped at 2,000 per lookup and 100,000 per job.
• Requests that look like sequential number ranges or generated e-mail lists are rejected (suspected_enumeration).
• A daily cap per account applies (GET /v1/limits).
• Invalid, duplicate and suppressed numbers are reported per row and never checked.

How do I use it responsibly?

X is widely used under pseudonyms, and people have good reasons for that. Never use this check to link a number to a pseudonymous account or to find out who is behind one. We don't support that: there are no reverse lookups, and the answer is only yes, no or unknown. Check only numbers you have a lawful reason to process. The acceptable use policy forbids stalking, harassment, profiling and unsolicited messaging. Anyone can object at /opt-out.

Example request

With a test key, +447700900001 answers "registered". See test mode.

curl https://api.mobilevalidate.com/v1/lookup \
  -H "Authorization: Bearer mv_test_publicSandboxn9ZgneuhR1B9CRfKG3fulym" \
  -H "Content-Type: application/json" \
  -d '{"numbers":["+447700900001"],"checks":["x"]}'

// npm install mobilevalidate · Node.js 20+ · save as check.mjs and run: node check.mjs
import { MobileValidate } from "mobilevalidate";

// Omit apiKey to read MOBILEVALIDATE_API_KEY from the environment.
const mv = new MobileValidate({ apiKey: "mv_test_publicSandboxn9ZgneuhR1B9CRfKG3fulym" });
const { data, error } = await mv.lookup({
  numbers: ["+447700900001"],
  checks: ["x"],
});
if (error) console.error(error.code, error.message);
else console.dir(data.results, { depth: null });

// Node.js 18+, Deno, Bun or the browser console (ES module: save as .mjs or use "type": "module").
const res = await fetch("https://api.mobilevalidate.com/v1/lookup", {
  method: "POST",
  headers: {
    Authorization: "Bearer mv_test_publicSandboxn9ZgneuhR1B9CRfKG3fulym",
    "Content-Type": "application/json",
  },
  body: JSON.stringify({ numbers: ["+447700900001"], checks: ["x"] }),
});
console.log(res.status, res.headers.get("x-request-id"));
console.dir(await res.json(), { depth: null });

# pip install mobilevalidate-sdk
from mobilevalidate import MobileValidate

# Omit api_key to read MOBILEVALIDATE_API_KEY from the environment.
mv = MobileValidate(api_key="mv_test_publicSandboxn9ZgneuhR1B9CRfKG3fulym")
result = mv.lookup(numbers=["+447700900001"], checks=["x"])
print(result)

<?php
$ch = curl_init('https://api.mobilevalidate.com/v1/lookup');
curl_setopt_array($ch, [
    CURLOPT_POST => true,
    CURLOPT_RETURNTRANSFER => true,
    CURLOPT_HTTPHEADER => [
        'Authorization: Bearer mv_test_publicSandboxn9ZgneuhR1B9CRfKG3fulym',
        'Content-Type: application/json',
    ],
    CURLOPT_POSTFIELDS => json_encode([
        'numbers' => ['+447700900001'],
        'checks' => ['x'],
    ]),
]);
$response = curl_exec($ch);
echo curl_getinfo($ch, CURLINFO_RESPONSE_CODE), PHP_EOL, $response, PHP_EOL;

package main

import (
	"fmt"
	"io"
	"net/http"
	"strings"
)

func main() {
	body := strings.NewReader(`{"numbers":["+447700900001"],"checks":["x"]}`)
	req, err := http.NewRequest("POST", "https://api.mobilevalidate.com/v1/lookup", body)
	if err != nil {
		panic(err)
	}
	req.Header.Set("Authorization", "Bearer mv_test_publicSandboxn9ZgneuhR1B9CRfKG3fulym")
	req.Header.Set("Content-Type", "application/json")
	res, err := http.DefaultClient.Do(req)
	if err != nil {
		panic(err)
	}
	defer res.Body.Close()
	out, _ := io.ReadAll(res.Body)
	fmt.Println(res.Status, string(out))
}

require "net/http"
require "json"

uri = URI("https://api.mobilevalidate.com/v1/lookup")
req = Net::HTTP::Post.new(uri)
req["Authorization"] = "Bearer mv_test_publicSandboxn9ZgneuhR1B9CRfKG3fulym"
req["Content-Type"] = "application/json"
req.body = JSON.generate({
  "numbers" => ["+447700900001"],
  "checks" => ["x"]
})

res = Net::HTTP.start(uri.host, uri.port, use_ssl: true) { |http| http.request(req) }
puts res.code, res.body

Response (excerpt, test mode: the first item of results):

{
  "kind": "phone",
  "input": "+447700900001",
  "e164": "+447700900001",
  "country": "GB",
  "number_status": "valid",
  "checks": {
    "x.registered": {
      "service": "x.registered",
      "status": "completed",
      "registered": true,
      "attributes": null,
      "confidence": "high",
      "confidence_score": 0.99,
      "checked_at": "2026-09-25T14:25:30.665Z",
      "cached": false,
      "age_seconds": 0,
      "billed": false,
      "reason": null,
      "poll_after_ms": null
    }
  },
  "test": true
}