Caller ID Check
Call a test number and see the caller ID your call arrives with, or that the number is withheld. The call is rejected as busy and never answered.
Overview
A phone call carries a number, and the phone being called shows it. In telephone networks this is CLIP, Calling Line Identification Presentation; withholding it is CLIR. What a caller sends is not always the number of the line: a business phone system may send its main number, or another number the business holds, instead. The Caller ID Check shows what actually arrives.
It is useful after setting up a phone system or a SIP trunk, to see that calls go out with the intended number; to confirm that withholding works; and to see what a mobile phone sends from abroad.
Web interface
- Get a number sets one of the 3 test numbers aside for you for 5 minutes. It is shown in international form,
+49 211 …, which reaches it from any country, with the form dialled within Germany beneath. On a phone, a tap on it starts the call. - While the page waits, it counts down the time left and asks the server every two seconds whether the call has arrived. Cancel gives the number back.
- The result shows the caller ID in large type, grouped as its country writes it, with its country and line type, then the number in each written form and when it arrived.
- Check again gets a new number, for a second call with the number withheld or from another phone.
| Message | When |
|---|---|
All 3 test numbers are in use right now. Try again in 2:40. | every number is reserved; the time is until the first one is free |
Too many numbers asked for from this address. Try again in 9:15. | more than 6 numbers from one address in 15 minutes |
No call arrived in 5 minutes, so the number was given back. Get a new one to try again. | the reservation ran out |
This tool is currently unavailable. | the check is switched off |
How it works
Every call to a test number is rejected as busy the moment it arrives, so it is never answered and never reaches a person, whether the number is reserved or not. The caller ID the call arrived with appears on the page that reserved the number called.
A number is reserved for one visitor at a time, and one address holds one number; asking for another gives the first one back. The first call to a reserved number is the one shown, and the number is free again as soon as it has arrived.
Reading the result
| Row | What it is |
|---|---|
| Country | the country the number belongs to, with its calling code, Germany, +49 |
| Line type | mobile, landline, internet telephony, toll-free and so on, as the country's numbering plan assigns the range; left out where the plan does not say |
| International | grouped as the country writes it, +49 1511 2345678 |
| National | as dialled within that country, 01511 2345678 |
| E.164 | the international standard form, without spaces, +4915112345678 |
| As transmitted | the caller ID exactly as it arrived: digits with the country code, 4915112345678, or anonymous |
| Arrived | when the call reached the test number, in your time zone |
The line type follows the range a number belongs to, not the network, so a mobile number moved to another provider is still a mobile number. A number the plan does not give out, such as one from the ranges set aside for films, is shown as sent and marked Not in the numbering plan; a phone system set to send a number of its own can produce one.
Withheld means the call carried no number. Another number than your own means your phone or phone system sends one it has been set to; the person you call sees that one as well.
Limits
- 3 numbers can be reserved at the same time, each for 5 minutes.
- The call is rejected as busy straight away, so it is never answered and normally costs nothing. Should your provider charge for it all the same, it is billed as a call to a German landline; your provider can tell you the rate.
- The check shows what arrives at a German landline number. Another network may in rare cases receive a number in a different form, and a number the network knows but does not present is never shown.
- Someone else who calls the number reserved for you, in those few minutes, is the call that is shown. The numbers are used for nothing but this check.
No API
There is no public API for this tool. The check needs a real phone call, and its endpoints serve only the page that reserved a number.
Privacy
Your number reaches this site through the phone network. It is kept in a temporary file on the server until the page that reserved the test number has shown it, which then deletes it at once, and for no longer than two minutes in any case. It is never logged. To limit how often numbers are asked for, a keyed hash of your address is kept for 15 minutes, never the address itself. The privacy policy has the details.