Seeded random number generator — the same seed gives the same numbers

How to use the seeded random generator

1. Type a Seed: any word, phrase or number, such as class-raffle-2026. Capital letters and spaces count.
2. Set the Minimum and Maximum. Both are included.
3. Choose How many numbers (1 to 1,000) and tick No repeats if each number may appear only once.
4. The result updates as you type; there is no button. Copy the numbers, and note the seed and settings so others can repeat the draw.

What it does and when to use it

Use it when a draw must be checkable: a class raffle, a team sports order, a random sample for a survey or an audit, or picking which questions go on a test. Share the seed and settings, and anyone can confirm the result. Developers and teachers also use seeds to make the same “random” data set every time, so a bug or an exercise can be repeated exactly.

When repeatability does not matter, the random number generator draws fresh numbers from your browser’s secure source each time. To draw names rather than numbers, give each person a number first, or use the random picker.

How it works

The seed text is turned into four 32-bit numbers by a hash called cyrb128. Those four numbers are the starting state of sfc32, a small, fast pseudo-random generator. Each step of sfc32 gives a new 32-bit value that depends only on the state, so the same seed always produces the same sequence.

To fit values into your range without favouring low numbers, the tool uses rejection sampling: raw values from the uneven top end are skipped. With No repeats, values already used are also skipped. This is why the first numbers stay the same if you only change How many, but changing the range or No repeats changes the whole list.

Worked examples

A class raffle. Seed class-raffle-2026, 1 to 30, 5 numbers, No repeats: always 24, 28, 18, 4, 5.

Repeats allowed. Seed abc, 1 to 100, 3 numbers: always 77, 14, 14. The repeat is part of the sequence; tick No repeats to skip it.

An impossible request. Seed abc, 1 to 5, 6 numbers with No repeats returns “Only 5 distinct values exist in this range.”

Limits and tips

• Whole numbers only; decimal limits are rounded.
• The range can hold at most 4,294,967,296 values.
• Record the exact seed. Raffle and raffle give different numbers.
• The list shuffler is quicker if you just need a random order.