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Open the gridmapper.svg file using your browser and you have a very simple dungeon mapping tool.

  • quick keyboard navigation
  • support for multiple levels
  • collaboration with others

The user interface comes with a help screen explaining all the details, and a link to a demo. The map icons are inspired by the icons in Moldvay's Basic D&D. There's a screenshot in this review on RPG Geeks. Here's a Master Dungeon Mapping Key PDF, if you want something more recent.


Table of Contents

It's Free

Also note that Gridmapper is totally free and gratis. It costs nothing to use, and you can do with it what you want. You can copy, modify, distribute and perform the work, even for commercial purposes, all without asking permission.

Keyboard Focus

Gridmapper was designed to be usable with the keyboard. And yet, the mouse can be important to move around on a large map and to draw rough outlines.

The help screen is supposed to help mouse users. You can click most tiles and they'll get inserted at the current position. If you use the mouse to position the pointer on the map, the pointer will follow the mouse as you move to the right in order to pick a tile. Press the Alt key to prevent the pointer from following the mouse.

Remember that sometimes you need to click the letter in order to rotate an element.

Internet Explorer Issues

Written using Vanilla JS. Unfortunately, Internet Explorer isn't well supported. That's because Gridmapper mixes SVG and XHTML in the same document and that appears not to work for IE. I'm trying to simply remove the stuff that doesn't work.

Chrome Issues

When zooming in or out, the text area will not get moved along with all the other elements. As far as I am concerned, this is a Chrome bug.


You will have noticed that those example URLs contain a lot of gibberish past the questionmark. This is the URL's query string. It's a sort of code that's very close to a stream of keyboard commands. You can get this link by clicking on Prepare Link and then clicking on the resulting Link. Perfect for sharing and bookmarking.

For more examples, check out this Google+ Collection.

How to Collaborate

Gridmapper allows multiple people to draw on the same map. In order to do this, you must all type the same map name into the text area and click the Join link. You probably still need a way to talk or chat online.


Alternatively, one of you opens Gridmapper, provides a name in the text area and clicks Join. The others connect to the Gridmapper Server and click on the map, there.

If you want to keep it private, put a password on the second line.

How to Save

This being a very simple web application, it has no access to your file system. And worse: If you use "Save As..." in Firefox or Chrome you'll save a copy without any of the changes you made!

These are your options:

  • Click on Save. This will save your map on the wiki. This also makes it public because anybody can look at the Gridmapper Campaign Wiki. Thanks for sharing! It may also not be what you want if your players are watching the wiki. This does not work for Internet Explorer and it does not work if you are using a local copy of Gridmapper. Please provide some information in the text area: put the dungeon name on the first line, your name on the second line, and a description on the third line. Example:
Demo Dungeon
Alex Schroeder
First draft
  • Click on Download and click on the resulting TXT link. This saves the current map as a text file. Use this if you don't want to save your map to the wiki. When you want to continue working on your map, use drag and drop to get the map into the text area and click Import. This does not work for Internet Explorer.

  • Click on Download and click on the resulting PNG link. This downloads an image of the current level. This is what you would use if you wanted to continue working on your dungeon using Gimp or Photoshop. Remember, if you want to print the dungeon, you need 300 dpi or 300 pixels per inch. You're probably better off using the SVG file and converting it to PDF. This does not work for Internet Explorer.

  • Click on Download and click on the resulting SVG link. This is also what you would use if you wanted to continue working on your dungeon using an SVG editor such as Inkscape. This will also allow you to save the map as a PDF file. This does not work for Internet Explorer.

  • If you're using Safari, you can just save the page. This will create a webarchive.

  • Click on Export and copy the content of the text area into a text file. When you come back later, paste the text file into the text area and click Import. This text file is basically a little script recreating your dungeon. This does not work for Internet Explorer.

  • Click on Link and bookmark the new page. The link now basically contains a little script recreating your dungeon. You might have to use a URL shortener such as when pasting the URL into a chat window or when sharing it on social media. As browsers and web sites have size limitations on the length of a link, this will not work for big dungeons. This is what you would use for quickly sharing a link.


It's possible to use the text area for some simple scripting. Paste the following in the text area, for example, and use Ctrl Enter as you move around on the map. It will surround your current square with walls.

[-1,-1]fff[-3,1]f f[-3,1]fff[-2,-1]

Scripting works by typing the commands you would need to type, with the following additions:

  1. f will place a floor and automatically advance (like a right arrow)

  2. - will move left by one (like a left arrow)

  3. . is used to stop rotations; thus ddd will place a door and rotate it three times where as d.dd will place one door and a second door, and rotate it once

  4. ; is used to pause for half a second; it might be useful if you're writing a demo for somebody else

  5. (x,y) or (x,y,z) will automatically move to the new position (be sure to add 0.5 to either x or y in Wall Mode); note that (0,0) is the top left corner and positive y is down

  6. [dx,dy] will move the current position relative to the current position; given that positive y is down, [0,1] is the equivalent of moving one down

  7. X[dx,dy] wipe the rectangle to the right and down (no negative coordinates).

How to extend Gridmapper

Let's assume you want to add wells as variants of statues to Gridmapper – and let's assume this had not yet been implemented. How would you do it?

Step 1: Find the SVG definition of a statue and add the SVG you want right next to it. Where to learn about SVG? Personally, I usually just look at these sources:

  1. The SVG Specification
  2. The SVG tutorials by Jakob Jenkov
  3. The SVG section on the Mozilla Developer Network

The outermost element needs to have an id attribute that you will be referring to later. It also needs a width attribute. This is used to scale your element.

Thus, here's a little SVG element containing the white floor rectangle and two circles. The outermost element has both an id and a width attribute.

<g id="well" width="100">
  <rect width="100" height="100" fill="white" stroke="black" stroke-width="10"/>
  <circle cx="50" cy="50" r="25" fill="black"/>
  <circle cx="50" cy="50" r="15" fill="black" stroke="white" stroke-width="10"/>

Step 2: Register the variants. What we need to do is tell Gridmapper that hitting v on a statue will turn it into a well and hitting v on a well will turn it into a statue. Find the variants in the source code and add the following:

variants: {
  'statue': 'well',
  'well': 'statue',

Step 3: Document it. Find the section at the end where all the tiles are documented. Search for #statue. Then, append something like the following:

<a xlink:href="javascript:interpret('bv')" title="well">
  <use x="40" y="1" xlink:href="#empty"/>
  <use x="40" y="1" xlink:href="#well"/>

Save it, test it, you're done!

Installation on your own Web Server

Since the query string is of utmost importance, the limitations on request length probably needs to raised. By default, Apache 2 has a limit of 8190 for these two options. I've increased them as follows in my web server config file:

LimitRequestLine      32000
LimitRequestFieldSize 32000

If you want hosting to work, you'll need to install as a Mojolicious app using Hypnotoad. You cannot use Toadfarm, because it's important that the server use only one instance. All the hosts and clients are in-memory. Nothing is saved to the disk. Remember to change the hostname and port at the top of the file.

If you're using Apache 2.2.22 (Debian Wheezy) as a proxy, you're in trouble. The gridmapper-server itself is using HTTP on port 8082 and the /join and /draw URLs are using WebSocket. This requires mod_proxy_wstunnel. This required recompiling a patched Apache and copying both mod_proxy and mod_proxy_wstunnel. You can find some links on my blog post.

Apache config:

ProxyPass /gridmapper-server/join ws://
ProxyPass /gridmapper-server/draw ws://
ProxyPass /gridmapper-server

Starting Hypnotoad:


See Also

The project was the result of admiring Daniel R. Collins' original GridMapper 1.0.

This originally started as a Clojure project. You can find the Clojure code on the clojure branch.

There is also a branch called c2 which uses C2 to create a web application. Unfortunately, it doesn't scale well: when you use a 30×30 grid, it's too slow. I decided to move to VanillaJS.

There's also a very good looking, Flash based website with a similar interface called ANAmap.