Number portability: what a prefix can and cannot tell you

With number portability a subscriber keeps their number when they move to another carrier. The number's prefix then names the carrier its block was allocated to, not the one serving it. 107 of the 245 numbering plans list mobile number portability. In those, a table of prefixes — on this site or anywhere — answers who was allocated the number, and nothing more.

Where mobile numbers are portable

Plans that list mobile number portability, by the ITU's world zones. A plan not listed may still port numbers; the data records it where it is known.

Zone	Plans listing it	Plans
North America and the Caribbean	21 of 25	Antigua and Barbuda, Anguilla, Barbados, Bermuda, Bahamas, Canada, Dominica, Dominican Republic, Grenada, Jamaica, Saint Kitts and Nevis, Cayman Islands, Saint Lucia, Montserrat, Puerto Rico, Sint Maarten, Turks and Caicos Islands, Trinidad and Tobago, United States, Saint Vincent and the Grenadines, British Virgin Islands
Africa	8 of 64	Egypt, South Africa, Morocco, Benin, Ghana, Nigeria, Cameroon, Kenya
Europe	40 of 52	Greece, Netherlands, Belgium, France, Spain, Hungary, Italy, Vatican City, Romania, Switzerland, Austria, United Kingdom, Denmark, Sweden, Norway, Poland, Germany, Gibraltar, Portugal, Luxembourg, Ireland, Iceland, Albania, Malta, Cyprus, Finland, Bulgaria, Lithuania, Latvia, Estonia, Moldova, Armenia, Belarus, Serbia, Croatia, Slovenia, Bosnia and Herzegovina, North Macedonia, Czechia, Slovakia
Central and South America	14 of 31	Peru, Mexico, Argentina, Brazil, Chile, Colombia, Panama, Saint Barthélemy, Guadeloupe, Saint Martin, Ecuador, French Guiana, Paraguay, Martinique
Oceania and South-East Asia	5 of 30	Malaysia, Australia, New Zealand, Singapore, Thailand
Russia and Kazakhstan	2 of 2	Kazakhstan, Russia
East Asia and special services	4 of 11	Japan, South Korea, Hong Kong, Taiwan
West, Central and South Asia	13 of 30	Türkiye, India, Pakistan, Iran, Jordan, Kuwait, Saudi Arabia, Oman, Israel, Bahrain, Qatar, Azerbaijan, Georgia

What it changes in your code

Validation: nothing. A ported number keeps its digits, so it stays inside the plan's ranges and passes the same pattern (phone number regex).
Line type: nothing, in most plans. Mobile numbers port between mobile carriers and stay in mobile ranges. The +1 plans are the exception: numbers move between fixed, mobile and VoIP carriers, so the line type an exchange was allocated as can differ from the line today. In area code 415, 213 exchanges were allocated as mobile and 484 as fixed line; any of their numbers may have moved (area code 415).
Carrier: the original one. Where the country pages, the area code pages and the checker name a carrier, it is the carrier the block was allocated to. That is right for statistics, for a default, for a rough guess; it is wrong for routing a message, pricing it per network, or telling a user which network they are on.
In service or not: no table knows. A valid number may be unassigned, disconnected or recycled to a new subscriber. Only the networks know.

What an HLR lookup and an MNP query answer

HLR lookup: The Home Location Register is the database of a GSM or UMTS mobile network that holds its subscribers and where they can be reached; in 4G and 5G cores the HSS and the UDM play the same role. An HLR lookup asks the network about one mobile number over the signalling network. Depending on the network it can answer whether the number is known and reachable, the mobile country and network codes (MCC and MNC) of the network that holds it — after a port, the new one — and whether it is roaming. Fixed and VoIP numbers have no HLR.
MNP query: Countries with portability keep a database of ported numbers, which carriers consult to route calls and messages to the right network. An MNP query asks it whether a number has been ported and to which carrier. It says nothing about whether the number is in service.
A prefix table: The allocation records the national plans publish: which carrier each block went to, as which line type. The same for everyone, free to read, and fixed until the regulator reallocates the block.

Sources: Recommendation E.164 and its supplements, Supplement 2: Number portability (ITU-T); National numbering plans, ITU-T E.164 (ITU). Portability as listed in the plans' data, 2026-10-25.