The GDMS goblin, a d20 in its eye socket, above the words Goblinoid Dungeon Mastering System

A storytelling companion for game masters and creatives of all sorts: a little seed of inspiration to get your brain whirring.

▶ Launch GDMS

Free · runs in your browser · works on phones · no sign-up

What it is

GDMS is a box of random tables you can roll in one keystroke. The innkeeper needs a name, the bridge needs a reason to be out, the chest needs something in it: roll, read, and keep playing. It gives you a spark when you need one and gets out of the way when you don't.

It's built in the spirit of classic and OSR games like Shadowdark, Old School Essentials and Maze Rats, and it looks and sounds like a computer from the era those games are nostalgic for.

GDMS with an NPC rolled: a name, a title, six ability scores, a drive, a flaw and a look
One roll of the NPC recipe: name, title, ability scores, drive, flaw and look.

How it works

  1. Pick a category. Encounters, NPCs, Dungeon, Town, Items, Weather and more.
  2. Roll. Press Enter or a number key, tap, or click the goblin in the corner.
  3. Use it. Pin the keepers to your Board. Step back through History to find something from earlier. Nothing is lost.

Three kinds of table

Tables
A list of entries, rolled like a die. Thirty swamp encounters is a d30.
Recipes
Several tables rolled together into one result. A dungeon name rolls a place, a descriptor and a thing: The Ruins of the Monstrous Elephant. An NPC makes twelve rolls at once.
Memory tables
Tables that remember where they left off. The weather drifts from one day to the next instead of leaping from blizzard to heatwave.

Made for the keyboard, fine on a phone

Every action has a key: number keys pick and roll, P pins, H opens history, O opens options, and the numpad works too. On a phone the same controls become buttons along the bottom, and the layout trims itself down to the result.

13 categories · 81 tables · 19 recipes · 4 memory tables · 6,836 entries in the core pack

GDMS on a phone, showing a swamp encounter

Make it yours

Look and sound

GDMS in the Amber theme
Amber, control panel
GDMS in the Notebook theme
Notebook, minimal
GDMS in the 95th window theme
95th window

Settings are saved in your browser, on your device.

Your own tables

Every table in GDMS is a plain text file you can open in any editor. A pack is a folder. Each folder inside it is a category, and each file is a table.

MyPack/
  Encounters/
    swamp.csv        a table
  NPCs/
    npc.json         a recipe
    _jobs.csv        starts with _ so it's hidden from the menu

A table is one entry per line. Put a number and a comma in front of an entry to make it more likely:

A hut on spindly stilts; smoke rises from its chimney
3,Will-o'-wisps bob over deep water, beckoning
# lines starting with # are notes to yourself

A recipe is a short file that names the tables to roll and how to put the results together:

{
  "type": "recipe",
  "title": "dungeonName",
  "parts": [
    {"label": "place",      "roll": "place.csv"},
    {"label": "descriptor", "roll": "descriptor.csv"},
    {"label": "thing",      "roll": "thing.csv"}
  ],
  "format": "The {place} {descriptor} {thing}"
}

Parts can also be left to chance (roll this only some of the time), repeated (roll it two to four times), and borrowed from any other category, so one table of names can serve every recipe that needs one.

The web edition runs the core pack. To roll your own pack in it today, get the source from GitHub and build it with your folder. It's the same format GDMS Pocket reads from its SD card.

Free, and yours

No account, no ads, no tracking. Your history, pins and settings stay in your browser. GDMS is made by Alexander Sousa in Providence, Rhode Island. If it earns a place at your table, you can support it on Ko-fi.

▶ Launch GDMS