Adding a World Border

There are many ways to display your world border on your map.
All of them work by adding a marker to the map, but some ways are simpler than others, at the cost of control or supported platforms.
This guide will list a few of the most common ways to add a world border to your BlueMap!

Manual in the config

This is the most supported method. This will work on every platform (Paper/Fabric/Forge/etc). Go to your BlueMap config directory, and open the maps folder. In there, you will find a .conf file for each of your maps.
Open the file that corresponds to the world that you want to add a world border to, and scroll to the bottom, until the marker-sets section.
Copy this snippet into there, and adapt it to your liking:

marker-sets: {
    world-borders: {
        label: "World Borders"
        toggleable: true
        default-hidden: false
        sorting: 0
        markers: {
            world-border: {
                type: "shape"
                label: "World Border"
                position: { x: 0, y: 64, z: 0 } # Center of your world
                shape-y: 64
                shape: [
                    { x: -1000, z: -1000 }  # Top-Left (North-West)
                    { x:  1000, z: -1000 }  # Top-Right (North-East)
                    { x:  1000, z:  1000 }  # Bottom-Right (South-East)
                    { x: -1000, z:  1000 }  # Bottom-Left (South-West)
                ]
                line-color: { r: 255, g: 0, b: 0, a: 1.0 }  # red
                fill-color: { r:   0, g: 0, b: 0, a: 0.0 }  # fully see-through
            }
        }
    }
}

For more information on how to create markers, please refer to the official Markers Guide.

Manual with commands

You can manually also create markers with the popular 3rd-party addon, BlueMap Marker Manager. (Available as a Paper plugin and as a Fabric mod.)
This addon allows you to create BlueMap markers via in-game commands, instead of via the config.

Create the marker set:

/bmarker set-create
/bmarker-setup-set id worldborders
/bmarker-setup-set map "world.(overworld)"
/bmarker-setup-set label World Borders
/bmarker-setup-set build

Create the world border marker:

/bmarker create shape
/bmarker-setup id worldborder
/bmarker-setup label World Border
/bmarker-setup marker_set "worldborders_world.(overworld)"
/bmarker-setup add_edge -1000 1000
/bmarker-setup add_edge -1000 -1000
/bmarker-setup add_edge 1000 -1000
/bmarker-setup add_edge 1000 1000
/bmarker-setup height 64
/bmarker-setup line_color 255 0 0 1
/bmarker-setup fill_color 0 0 0 0
/bmarker-setup build

Automatic with BlueBorder

There is a much simpler way to add a world border, if you’re using the vanilla world border: you can install the BlueBorder plugin!
It automatically adds a world border marker at the position of your world border, without any commands or configuration necessary!
You can choose the colour for your border in the config file.

Automatic with BlueBridge

BlueBridge is another plugin that can add a marker where your vanilla world border is. Download BlueBridgeCore.jar and BlueBridgeWB.jar, and place them in your plugins folder.
For more information on how to use this plugin, please visit its wiki.

Automatic with ChunkyBorder

If you’re not using the vanilla world border, you can also use Chunky and its extension ChunkyBorder to add a world border.
You can then create a world border like this:

/chunky radius 1000
/chunky border add

or like this:

/chunky world the_nether
/chunky shape circle
/chunky radius 1000
/chunky border add

For more information on how to use Chunky and ChunkyBorder, please visit their respective wiki’s: Chunky Wiki and ChunkyBorder Wiki
You can choose the colour for your border in the config file.

If this is an Earth map that you got from from earth.motfe.net, then you can find the exact commands and coordinates to add your border on this website: docs.apocmc.us/minecraft-earth-map/map-borders
Please note that you do not have to run /chunky start, though, like this website suggests!