usefulweb.site Random Generator

Everyday calculators

Random Generator

Random numbers, dice, coins, list picks, shuffles, fair teams, dates, strings and UUIDs.

Numbers, rolls, flips, picks, dates, strings or UUIDs.

NdS±M, e.g. 2d20, 4d6+2, d100.

Empty = cryptographic randomness, different every time. With a seed, the same settings always give the same result — never use seeded output for passwords or keys.

Default: now (UTC). Set it together with a seed for reproducible v7 UUIDs.

Try an example: Lottery 6 of 49 (seeded) · Roll 4d6+2 five times (seeded) · Balanced teams by skill (seeded) · Three UUID v4 (seeded)

How it works

Generates random whole or decimal numbers (optionally unique), dice rolls such as 3d6+2, coin flips, picks from a list, shuffles, balanced teams (by optional skill), random dates, strings and UUID v4/v7. Uses cryptographic randomness by default; with a seed the output is reproducible so others can verify a draw.

  • Without a seed, bytes come from the server's cryptographically secure generator (Node.js crypto.randomBytes); nothing is stored. With a seed, bytes come from SHA-256 in counter mode over the seed, so anyone can reproduce the draw with the same seed and settings.
  • Whole numbers in a range use rejection sampling (no modulo bias). Decimals use 53 random bits scaled into [min, max) and rounded to the chosen places. Unique numbers use a partial Fisher–Yates shuffle or Floyd's algorithm for huge ranges.
  • Shuffles and picks use Fisher–Yates. Teams: without skills, a random round-robin; with skills, a snake draft over a random order followed by swaps that shrink the gap between the strongest and weakest team.
  • UUID v4 has 122 random bits; UUID v7 has a 48-bit Unix millisecond timestamp and 74 random bits (RFC 9562).

Seeded output is predictable by design. For passwords or keys, leave the seed empty (or use a dedicated password generator on your own device).

Sources

For scripts and AI agents

  • JSON API: POST https://randomgenerator.usefulweb.site/api/v1/calculate (same calculation as this page)
  • Interface description: OpenAPI 3.1 · AI guide: llms.txt
  • MCP server (Streamable HTTP): https://randomgenerator.usefulweb.site/mcp · tool name random_generator
Example request
curl -s -X POST https://randomgenerator.usefulweb.site/api/v1/calculate \
  -H 'content-type: application/json' \
  -d '{"mode":"integers","count":6,"min":1,"max":49,"unique":true,"seed":"draw-2026-10-18"}'

Related tools

  • Elo/Glicko Rating Lab – Rate players from game results with Elo, Glicko-1 and Glicko-2; history chart and win odds.
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