International Carrier Lookup: Checking Numbers Across Countries

A practical guide to running an international carrier lookup on mixed-country phone lists, from E.164 formatting to choosing between realtime and bulk file checks.

An international carrier lookup works best when every number is written in E.164 form, with a leading plus sign, the country code and the subscriber number. CarrierLookup returns the carrier each number was originally allocated to, plus line type and allocation geography. Realtime checks accept numbers from different countries in one request, while bulk file tasks are built around one selected country per file. The result is original allocation context, not the network that serves the number today.

Start with clean E.164 input

Every international carrier lookup depends on the country code being present. The E.164 format starts with a plus sign, followed by the country code and the subscriber number, with no spaces, dashes or brackets. A national-format string such as a number beginning with a trunk zero cannot be placed in a country without guessing, so it should be converted before the lookup.

A short preparation checklist for a mixed list:

• Add the plus sign and country code to every row.
• Remove spaces, punctuation and extension text.
• Drop obvious placeholders and blank rows.
• Keep the original source column so rejected rows can be traced back.

A rejected format is not a no-carrier result. It only means the input could not be read as a number, so fix the formatting and run it again.

Checking mixed-country lists in realtime

Realtime Original Carrier Lookup does not ask for a separate country selection, because the country code inside each number already carries it. A single number goes through POST /api/v1/check, and a synchronous multi request goes through POST /api/v1/batch-check with 1 to 100 numbers, even when they come from different countries. Results come back in input order, so they can be matched to the source rows by position.

The dashboard offers the same realtime multi lookup for up to 500 numbers at a time, which suits an analyst who has a pasted list and wants answers on screen.

In a multi response, each item reports whether a normal result exists. A missing normal result is not a statement that the number is invalid or disconnected. If a multi request times out, the whole request fails without partial results and the full amount is returned.

When to switch to a bulk file task

Bulk file tasks are asynchronous and suit large lists. A task takes a TXT or CSV file with one country-coded number per line and one selected ISO country. Because the task is scoped to a country, a global list should be split by country first, then submitted as separate tasks.

Preprocessing excludes invalid rows, duplicates, numbers without a country code and numbers outside the selected country. Excluded rows are not charged. A task moves through processing, success or failed, and a successful task returns one downloadable CSV. Poll the task status no more often than every 30 seconds.

Per-product limits apply to file size and number counts, so check the current API documentation before planning a very large upload.

Regional notes and what the output means

Coverage is not identical everywhere. Realtime single-number checks support mainland China (+86), Hong Kong (+852) and Macau (+853) for small volumes, while bulk file tasks do not support these regions. Taiwan (+886) support is unconfirmed, so test a small sample before including it in a plan.

A quick way to choose a route:

When reading results, treat the carrier as the original allocation, and region and city as number-range geography. Neither describes where a person is, and neither establishes that a number can receive calls or messages.

FAQ

Can one request contain numbers from several countries?

Yes for synchronous multi requests. A multi request accepts 1 to 100 E.164 numbers, and they can come from different countries. Bulk file tasks differ, because each task is built around one selected country, so a global list should be split before submission.

How can teams handle numbers that return no normal result?

Keep them in a separate review list. Teams can recheck the formatting, confirm the source of the number, and treat the carrier column as unknown rather than negative.

Does an international carrier lookup show the current network?

No. CarrierLookup reports the carrier a number range was originally allocated to. After a number is ported to another network, the original carrier stays the same. The result is useful for segmentation and data enrichment, not for deciding which network currently serves a number.

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