What do I do with the map file?

1. Create a map in minecraft
2. Go to the save folder of your world
3. Replace in the data folder there the created map_[i].dat with the downloaded one. ([i] is the number of the map)
4. Load the world in minecraft and enjoy your map

How is the map file created?

mc-map-item-tool uses node-nbt to create a file in the nbt format (which is being used by Minecraft) from a Javascript object.

What technologies are being used?

We use here among other things the HTML5 File Api, Web Notifications, Canvas, Javascript (jquery and bootstrap for the layout, nodejs on the server, Colour.js to adjust the colors for Minecraft)

I have found an error or want to make a feature request

Just make a pull request on github or create an issue ticket there.

How does a map item made by this tool look in minecraft?

You can see some examples here.

Why does the tool ask me how many maps I already have in my world?

This number is used to give the downloadable map files the correct file name. If you want for example to replace map number 7 in your world you just have to input "7". When you use the split-image feature, all map files in the downloadable zip archive will get their number according to your input: If you input "7" and split the image into 4 parts the files will have the numbers 7, 8, 9 and 10.