Steve September 26, 2020

TreeLine is an outliner for Linux and Windows that is flexible enough to sit at the heart of any operation. It allows you to store almost any type of information (plain text, rich text, HTML, numbers, dates, times, booleans, URLs, etc.) and comes with a tree structure to help keep things organized.

Here, we show you how to install TreeLine, and how to use it, by setting up a project, building its structure, then adding content ready for sorting and search later.


For Windows, you can download the installer from its website and install it. During the installation, we recommend keeping the “Create an uninstaller” option.

For Linux, TreeLine is available in the repository of many distributions, so you can easily install from the Software Center/Package Manager. Alternatively, you can download the archive from its website, extract it and run the command:

Interface basics

The main interface is spare, featuring a menu bar, toolbar and three mostly empty panes. The third pane on the right has a tabbed interface at the bottom providing access to output, editing and Title list. 

Screenshot showing the main interface of TreeLine.

By default, each pane has the word “Main” in it, and this is the root of your document. This is great if you want to start with a blank slate. You can also go to “File -> New” to see a small selection of template projects including a ToDo list, Long text (good if you’re planning a novel), a contact list and Book list. A scan through these will give you a good indication of how the structuring works. Essentially you have a tree of parent and child nodes that contain your dataset.

Working windows

The top pane provides a breadcrumb trail to the current datapoint or card. It’s really useful when projects begin to get more ambitious.

On the left is the tree, which provides an overview of the structure and allows you to navigate down to individual cards.

On the right is the data itself. Generally, you’ll see the Data Output tab, which is a simple card showing the information. “Data Edit” exposes the form behind the data, allowing you to make changes. “Title List” displays the title of the current node and any child nodes beneath it.

Create a project

For this sample project, we’re going to create an inventory to organize our iPad synthesizer collection. While our datapoints may differ, the methods will be the same.

Windows screenshot showing the data edit window of TreeLine.

We’ll start by renaming the root node. There are a couple of ways to accomplish this. You can right-click a node title in the left pane and select “Rename” or click the note, then in the right pane choose the “Data Edit” tab to see the title field displayed.

Add structure to your data

To begin, go to “Data -> Configure Data Types.” In the Type list is the data type which will be called Default. We can change the name by hitting “Rename Type” and giving it a more useful name. 

Select the “Type Config” tab, where you can define some output options such as allowing HTML in long text fields, set a default child type and change the icon for the node.

Choose your fields

In the Field List tab, we finally come to the point where we create the data structure for each node. Make sure the correct data type is selected at the top and select “New Field” from the buttons on the right.

Screenshot showing the data structure in our TreeLine Synth project.

You can come back later and append or adjust these fields, but that might mean backporting new data into your nodes, so it’s best to think through your data structure before committing to it.

Define the data

Next we’ll shift into “Field Config” to set up each of the fields in turn. Breaking down the interface in this way can feel convoluted, but in our experience it allows for a degree of intention in setting things up – almost forced to think about how you’re going to use this data in the future.

Screenshot showing the configuration screen for a 'Choice' field in TreeLine.

Select the Data Type and Field, then define the Field Type on the second row. The selection here is going to change the Output Format options next to it. The standard Text field has no output options, but if you choose, for example, the Number element, you can define the way numbers are displayed. By default, numbers are set to “#.##” which allows input to two decimal places, but you can change this to suit your needs. For example, in our “Voices” field, we just need an integer so can change it to #.

Where we have a binary (Yes/No) option, we use the Choice option and in the output format add “Yes/No,” where the slash is the separator between the choices. You can, of course, have multiple options here. The Format Help button will show you how to fill in this dependent on your Field Type.

For text fields, you can also include a Prefix and Suffix and set the number of lines available in the editor.

Adding data

Now that you have structure in place, you can begin adding data. Back in the main interface, right click on your root node and select “Add Child.” Provide a name for the node and hit Enter. Ctrl + I will create a “sibling” node beneath your original, which can also be named.

Eventually, we get to adding data to the project, as this screenshot shows.

Next, select one of your nodes, select Data Edit on the right pane and begin adding your data. Text fields take text, your Choice fields will include a drop-down selector, and number fields will format as you’ve set them.

TreeLine is the kind of software you don’t realize you need until you begin using it. If you’re an inveterate lister, it could be the perfect host for your next epic inventory.

If you just want a simple note-taking app instead, do check out CherryTree or Joplin Notes.


Andy Channelle

Andy Channelle is a writer and web developer who has written for Linux Format, Mac Format, 3D World and others, and has also published best-selling books on Ubuntu Linux and He’s recently worked on web projects and campaigns for the International Red Cross and the UN. He produces – but hardly ever releases – electronica under the name Collision Detector. Andy lives in Wales, UK.

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