Seeded Random Number Generator
Enter a seed and get the same sequence every time, which is what testing and shared demos need.
Seeded Random Number Generator
Seed random-nr, 1 to 100
Seed and range
The same seed always gives the same sequence
How many numbers
How to use the seeded generator
- Enter a seed, anything from a word to a number, and set the range.
- Generate. The same seed always produces the same sequence.
- Change the seed for a completely different, but equally repeatable, sequence.
What is a seeded random number generator
A seeded random number generator takes a seed you enter and returns the same sequence every time that seed is used. Type any seed, set your range and count, and Random Nr reproduces an identical draw on demand, which is exactly what automated testing, shared demos and reproducible research need.
When to use repeatable randomness
Most of the time random means unpredictable, but sometimes you need the opposite: a sequence that looks random yet comes back identically every time. That is what a seed gives you.
| Situation | Why a seed helps |
|---|---|
| Software testing | a failing test reproduces the same random inputs every run |
| Shared demos | two people entering the same seed see the same result |
| Game levels | a seed recreates the exact same generated world |
| Research | published work can be rerun and verified from the seed |
The famous example is the game Minecraft, whose entire world is generated from a single seed, so sharing the seed shares the world.
How a seed becomes a sequence
The seed text is hashed into a starting number, which drives a small deterministic generator, here a well tested routine called mulberry32. Because the arithmetic is fixed, the same starting number always retraces the same path, while a different seed sends it somewhere else entirely. The output still passes for random and spreads evenly across your range, but it is fully determined, which is the whole point.
Why seeded numbers are pseudo random
A seeded sequence is pseudo random by design: reproducible is the feature, not a flaw. When you need genuine unpredictability instead, for a draw or a key, use the random number generator or the secure random generator, neither of which can be replayed.
More number generators
Frequently asked questions
What does the seed do
It fixes the sequence. The same seed always produces the same numbers, so a run is repeatable.
Is a seeded draw still random
It is pseudo random. The spread looks random, but it is fully determined by the seed, which is the point when you need to reproduce it.
When should I use a seed
For tests, debugging and shared demos where everyone should see the same result. For a truly unpredictable draw, use the standard generator.
Can I sort the output
Yes. Sorting orders the display without changing which numbers the seed produced.
Is it free
Yes, free and with no sign up.
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- True Random Number Generator
- Secure Random Number Generator
- Normal Distribution Generator
- Random Sample Generator
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- Permutation Generator
- Random Number Generator
For an unpredictable draw use the random number generator, and to weight the odds see the weighted generator.