Minecraft
Whitelist & Ops Builder
The whitelist file wants UUIDs, not names, and finding twenty UUIDs by hand is twenty visits to a lookup site. Paste the names, get both files.
One per line, or separated by commas. Up to 20 at a time. Java Edition names only — Bedrock players do not have Mojang UUIDs.
How this works
Minecraft identifies accounts by UUID so that a rename does not silently drop someone off your whitelist. Each name is looked up against Mojang's public profile endpoint, and the result is formatted into whitelist.json and ops.json with the dashes the server expects — the API returns them without. Nothing here needs an API key, and no account data is stored.
What people get wrong
Operator level is the part to think about rather than skim. Level 1 only bypasses spawn protection; level 2 unlocks most cheat commands and command blocks; level 3 adds kick and ban; level 4 adds stop, op and deop — which means anyone at level 4 can shut your server down and promote themselves permanently. Also note that Bedrock players have no Mojang UUID, so a Geyser or Floodgate setup whitelists them differently and these files will not cover them.