Random Phone Generator
Reserved for fiction
The 555-0100 to 555-0199 block is reserved by the North American Numbering Plan and is not assigned to any subscriber.
The random phone generator produces numbers from the two ranges regulators have set aside for fiction: the US 555-0100 to 555-0199 block, and Ofcom’s 07700 900000 to 900999 drama range. Neither can reach a subscriber, which is the difference between test data and accidentally publishing somebody’s phone number.
How it works
- US: a real area code, then 555, then 01 and two digits. Only 555-0100 to 555-0199 is reserved. The rest of the 555 exchange is assignable.
- UK: the 07700 900xxx range, which Ofcom reserves for drama and which is never allocated to a mobile operator.
- Area codes used in the US format are real, so the numbers look plausible; the reserved subscriber block is what makes them safe.
The widespread belief that any 555 number is fake is wrong, and it is the reason fictional numbers regularly reach real people. Only the hundred numbers from 555-0100 to 555-0199 were ever set aside.
Examples
US numbers
Format
US
How many
4
Result
(415) 555-0142, (212) 555-0177, (702) 555-0103, (312) 555-0198
Area codes vary and are real, but every subscriber number falls in the reserved 0100-0199 block.
UK numbers
Format
UK
How many
3
Result
07700 900412, 07700 900037, 07700 900881
The 07700 900 prefix is fixed and the last three digits vary, giving exactly 1,000 possible numbers in the reserved range.
Frequently asked questions
Is every 555 number fake?
No, and this is the most consequential misconception about US phone numbers. Only 555-0100 through 555-0199 is reserved for fiction. The rest of the 555 exchange is assignable and some of it is in use, which is why film productions using numbers like 555-1234 have generated real nuisance calls.
What is the UK equivalent?
Ofcom reserves 07700 900000 to 900999 for drama, along with similar blocks for landlines. That range is never allocated to an operator, so calls to it fail rather than reaching anyone.
Will these pass phone number validation?
Format validation, yes. They are structurally valid numbers. A validator that checks whether the number is allocated and reachable will reject them, which is generally the outcome you are testing for.
Can I use one to sign up for a service?
No. Nothing can call or text these numbers, so anything requiring SMS verification will not complete. They are for seeding databases and filling in mock-ups.