About OTP Generator
OTP Generator produces one-time passcodes: numeric strings of a length you set, with leading zeros preserved so a four-digit code remains four characters. Up to a hundred can be generated at once, which is convenient for populating a test fixture or a spreadsheet of sample records.
Its proper use is as a source of realistic-looking sample data. Test suites need passcodes that look like the real thing in order to exercise validation, formatting and expiration logic, and generating them by hand is both tedious and error-prone.
For anything beyond that, be deliberate about the source of randomness. The digits here come from the ordinary pseudo-random generator rather than the cryptographic one, which is entirely adequate for placeholders and not adequate for a secret that protects a real account. If you need codes whose sequence cannot be predicted, they should be issued by a cryptographic source on a server, never by a page in the browser.
How to use OTP Generator
- 1 Choose how many digits each code should have, between four and ten.
- 2 Set how many codes you need.
- 3 Copy the list into the test data, a fixture or a spreadsheet.
Frequently asked questions
Can I use these codes for real two-factor authentication?
No. The digits come from an ordinary pseudo-random generator rather than a cryptographic one, so the sequence is predictable in principle. Real one-time codes must be generated server-side from a cryptographic source and a per-user secret.
Are leading zeros preserved?
Yes. A six-digit code that begins with zero is returned with the zero in place, which matters because stripping it would produce a five-character string that fails a length check downstream.
What length do real systems use?
Six digits is the most common, and eight is used where a longer window is needed. Both are offered, along with the shorter and longer lengths that some legacy systems still expect.
Free, online, and private
Free to use
OTP Generator is completely free. There is no account to create, no login, and no hidden charge or usage limit.
Runs online in your browser
It is a free online tool that runs entirely in your browser. Nothing to download or install — open the page and start using it right away.
Your data stays private
All processing happens locally on your device. Your input is never uploaded, stored, or tracked, so it never leaves your browser.
How OTP Generator behaves in detail
These are the specifics of this implementation — the exact ranges, defaults and fixed settings you are working with.
| Parameter | Value |
|---|---|
| Digits per code | 4 to 10, default 6, always padded to that exact width |
| Character set | digits 0–9 only — no letters and no symbols |
| Draw algorithm | floor(Math.random() × 10^digits), then padStart to the chosen width |
| Batch output | 1 to 100 codes, default 5, one per line |
Compiled from the implementation of this tool and checked against it by itoolnet.
What OTP Generator does not do
Knowing the edges of a tool saves more time than another list of its features. These are the cases where it will not do what you might expect.
- The entropy comes from Math.random(), a non-cryptographic generator, which is the wrong source for a code that guards an account — a real one-time passcode must be unpredictable to anyone who has seen earlier ones.
- Despite the name there is no one-time semantics here: no shared secret, no time step, no counter and no Base32 seed, so nothing produced can be checked against an authenticator app or an HMAC-based scheme.
- Codes are independent draws from 10^digits possibilities, so a short four-digit batch can repeat a value, and because of the zero padding a code such as 004821 is valid output that other systems may store as a number.
Tested and documented by itoolnet, the team that builds and maintains this site.