+ prefix, country code, and total digit length, then tells you
exactly why a number was rejected so you can fix it before sending.
What does this phone number validator do?
This validator checks whether a phone number conforms to the E.164 international standard — the
format required by virtually every SMS API. It strips spaces, dashes, parentheses, and dots; converts a leading
00 to +; validates the country code against a built-in map of 200+ dial codes; and flags
common mistakes like a leading zero after the country code. It also detects the likely country from the dial code
and reports the exact digit count.
It is a format validator only. It cannot tell you whether a number is active, reachable, or ported — for that you need an HLR lookup or phone number verification API, which queries the carrier network in real time. Think of this tool as the first line of defense: it catches the formatting errors that cause the majority of "invalid number" rejections, instantly and for free.
Format vs. reachability
E.164 validation proves a number is well-formed. An HLR lookup proves it is connected. Use both: validate format here, then verify live numbers with HLR before you pay to send.
Why does E.164 formatting matter for SMS APIs?
Every SMS gateway expects numbers in strict E.164 format: a plus sign (+), followed by the country
code, then the national number — with no spaces, dashes, or parentheses. A number like +14155552671
is valid; 1 (415) 555-2671 is not. When your API rejects a number, it is almost always a formatting
problem rather than a delivery problem, and this validator catches those issues before a single credit is spent.
The most common mistakes that trigger SMS API errors are:
- Missing the
+prefix entirely. - Using
00instead of+at the start. - Leaving a leading zero after the country code (e.g.
+447instead of+44). - Including spaces, dashes, or parentheses anywhere in the number.
- Too few or too many digits for the chosen country code.
For a deeper look at handling these failures in production, see our guide on SMS API error handling at three levels and the no-KYC SMS API complete guide for 2026.
How long can an E.164 phone number be?
Per the E.164 standard, a phone number must be between 4 and 15 digits total, including the country code. Most mobile numbers fall between 8 and 15 digits. Anything shorter than 4 digits or longer than 15 is automatically invalid and will be rejected by SMS gateways. This validator checks the length and warns you the moment a number is too short or too long.
How do I format a phone number for an SMS API?
Start with a plus sign, add the country code, then the national number with no separators. For example, the US
number (415) 555-2671 becomes +14155552671, and the UK number 07911 123456
becomes +447911123456. This validator converts common local formats — including 00
prefixes and spaced digits — into strict E.164 for you, so you can paste numbers exactly as your users type them.
Can I validate phone numbers in bulk?
Yes. The batch mode above validates an entire list at once — paste one number per line, click Validate All, and you get a table showing the converted E.164 form, a valid/invalid verdict, the detected country, and the reason for any rejection. You can then copy just the valid numbers with a single click, ready to drop into a bulk SMS campaign or an API request.
This is especially useful before importing a contact list. Cleaning formatting errors up front means fewer bounced messages, lower costs, and cleaner delivery reporting in your SMS API integration.
Which countries and dial codes are supported?
The validator ships with a built-in map of 200+ country dial codes, covering major messaging markets across
North America, Europe, Latin America, Asia, the Middle East, and Africa. Because detection is based on the longest
matching dial-code prefix, it correctly distinguishes overlapping codes such as +1 (US/Canada),
+44 (UK), +49 (Germany), +91 (India), and +971 (UAE).
If a number is well-formed but uses a code outside the built-in map, the tool still validates format and length — it simply leaves the country field blank. For live, carrier-grade coverage across SMSRoute's 149 active destinations, see the SMS pricing page.
Frequently asked questions
What is a phone number validator?
A phone number validator checks whether a number is formatted in valid E.164 standard — the format every SMS API expects. It confirms the plus sign, country code, and correct digit length, and flags common mistakes like leading zeros or stray characters.
Why do SMS APIs reject my phone number?
Most SMS APIs require strict E.164 format. The most common rejections are a missing + prefix, leading zeros after the country code, spaces or special characters, too few or too many digits, or an invalid country code. This validator catches all of those before you send.
Can this validator tell if a number is active?
No — this tool checks format only. It cannot verify whether a number is reachable, active, or ported. For that you need an HLR lookup or phone number verification API, which queries the carrier's home location register in real time.
What is the correct length for an E.164 number?
E.164 numbers are 4 to 15 digits total, including the country code. Most mobile numbers fall between 8 and 15 digits. Numbers shorter than 4 or longer than 15 are invalid and will be rejected by SMS gateways.
How do I format a phone number for an SMS API?
Start with a plus sign, then the country code, then the national number with no spaces, dashes, or parentheses. For example, the US number (415) 555-2671 becomes +14155552671. This validator converts common local formats to strict E.164 for you.
Is this phone number validator free to use?
Yes. The validator runs entirely in your browser, is free to use, requires no signup, and includes both live single-number validation and a batch mode for checking entire lists at once.