What is an OPML file and when should I use one?

OPML in one paragraph

OPML stands for Outline Processor Markup Language. It is an XML format for outlines: a file with a head, a body, and a nest of outline elements, each one holding a line of text and, optionally, children of its own. There is no picture in it, no color and no position, only the words and the shape of the hierarchy.

Mind map tools adopted it because it was already there. Long before visual mind maps, people wrote outlines in plain text, and OPML gave those outlines a standard way to be saved, emailed and opened by a different program. A mind map is an outline with lines drawn between the levels, so an outline format moves one naturally.

In Canvasola, OPML is one of the exchange formats for the mind map. Choose Export Mindmap OPML to write the file, and Import OPML… to read one that came from somewhere else. The Markdown export guide covers the other text route, which is friendlier when you are pasting into notes rather than moving between map tools.

• OPML is XML, so it is readable in any text editor
• The format holds text and hierarchy, nothing visual
• Canvasola both writes OPML 2.0 and reads OPML files
• It is the common ground between different map tools

Why mind map tools exchange OPML

Every mind map tool that promises import and export needs a format both sides can read, and OPML is the one most of them settled on. That is why a map you export from Canvasola can open in another mind map program, and why a file a colleague sends you can open here, without anyone retyping a branch.

The exchange is deliberately plain. There is a title, a tree of text, and nothing that ties the file to one particular program. That means the file stays readable years later, in a text editor if nothing else, which is the kind of durability a drawing file does not have.

The trade is that the visual layer does not travel. Colors, node icons, drawings, cross link tubes, notes and positions are all Canvasola features, and an OPML file carries none of them. What survives is the thinking: the labels and the branches.

Export a Canvasola map as OPML

Open the File menu and choose Export Mindmap OPML. The file downloads as canvasola-mindmap.opml, with a content type of text/x-opml+xml, and it opens in any text editor if you want to see what is inside it.

The export takes a second, and the file stays small, because it holds text rather than pixels. That is one of the reasons the format survived: a map with hundreds of branches is still a small file compared with a picture of the same map, and it can be attached to an email without drama.

Export the file before you start passing the map around, and export it again after a big change, because the OPML is a snapshot of the moment you took it. The complete Canvasola guide lists where the export options sit in the File menu.

1. Open the File menu. Choose Export Mindmap OPML from the File dropdown in the top bar.
2. Keep the file. Store canvasola-mindmap.opml with the project file, so the structure is available even if the app is not.

What is inside the file

Open the .opml file in a text editor and the structure is short. It starts with the XML declaration, then an opml element carrying version 2.0, a head holding a title, and a body holding the outline elements. Each outline element carries your node label in a text attribute, and any child outlines are nested inside it.

Two details are worth knowing. The title in the head comes from your root node, and the root node is also the first outline element in the body, so a reader that only looks at the body still sees the whole map. If your map uses more than one layer, the export adds a legend line at the top of the body naming the layers it used.

Layer membership travels as a tag on the label, in the form [layer:N] at the end of the text. A node on the first layer carries no tag, and a node on a deeper layer carries the number of its plane. The same tag appears in the Markdown export, so the two formats agree about how a layered map is written.

• An opml element with version 2.0 wraps the whole file
• The head holds a title, the body holds the outline elements
• Each node is an outline element with the label in a text attribute
• Layer membership appears as a [layer:N] tag on the label

Import an OPML file from elsewhere

Choose File, then Import OPML…, and pick the file. Canvasola reads the outline elements, rebuilds the tree, and drops you into a new map with the view fitted and the root selected. The nodes come in with palette colors assigned as the tree is built, so the imported map looks like a Canvasola map rather than a stranger.

Files from other tools vary, and the import is written to cope with that. A file that nests everything under a single root outline is read from that root. A file with several top-level outlines gets them as branches under one root named after the title in the head. The parser reads outline elements and their text only, so unrelated XML causes no trouble.

Before you import anything, save the work that is open, because the import takes over the canvas with a new map. The moving a project between devices guide covers keeping a project file safe while files move between machines.

• One root outline gives a map with that root
• Several top-level outlines become branches of one root
• The head title names the root when there is no single outline
• Importing replaces the map that was open

OPML versus Markdown versus plain text

All three formats carry the same thing: the labels and the hierarchy. What differs is what the receiving program expects. OPML is for programs that speak outline XML, and other mind map tools read it. Markdown is for text tools: notes, documentation and issue trackers, where a nested bullet list is the natural shape.

The plain-text outline is the plainest of the three, one label per line with indentation for depth, and it is the easiest one to read by eye and the easiest to fix by hand. It is also the one that loses the layer tags, so a multi-layer map should travel as OPML or as Markdown.

If you are choosing between OPML and Markdown for one specific job, the deciding question is simple: is the next program a mind map tool or a text tool? The document import guide covers the case where the source is neither and you need to build the outline first.

• OPML is for mind map tools, Markdown is for text tools
• The plain-text outline is the easiest to edit by hand
• Only OPML and Markdown carry the layer tags
• All three import back into a Canvasola map

Note: Nothing in the OPML file is proprietary, which is the point. A file you cannot open in a text editor is a file you have to trust, and OPML is designed to be read by anyone with five minutes and a text editor.

A checklist you can reuse

• The map was exported as OPML before it was sent to another tool
• The file canvasola-mindmap.opml was kept with the project file
• The file was opened in a text editor to confirm the structure
• Layer tags were checked on a map that uses more than one layer
• The project file was saved before importing over an open map
• The right format was picked for the program that receives the map

Common mistakes to avoid

• Expecting the visual design to travel. An OPML file holds labels and hierarchy. Colors, icons, notes, drawings and link tubes stay in the app, so keep the project file as well.
• Treating an old export as current. The file is a snapshot of the moment you took it. Export again after a big edit, and name the copies so you know which is which.
• Overwriting the map you were working on. The import takes over the canvas with a new map. Save the project file before you pick the file to import, or the previous map is gone from the screen.
• Hand-editing a file without checking the structure. A stray character inside a text attribute can make the whole file unreadable. Copy the file before editing it, and keep the export that worked.

Frequently asked questions

What is an OPML file used for?

It is a standard way of moving an outline between programs. Canvasola uses it to send a map to another mind map tool and to receive one back, and because the format is plain XML with no vendor lock-in, the file also stays readable in a text editor years after you exported it.

Is an OPML file the same thing as a mind map image?

No, and the difference is the whole point of the format. An image such as the PNG export shows you the map as a picture, and it cannot be edited or read by another program. An OPML file describes the same map as a tree of text, so another tool can rebuild it as a map of its own.

Does an OPML export keep my node colors and icons?

No. OPML carries the labels and the hierarchy, and nothing visual. Colors, icons, notes, drawings, cross links and positions stay inside the Canvasola project, so keep the .canv file as well whenever the visual version of the map matters to somebody.

Can I edit an OPML file by hand?

Yes, and it is a reasonable way to fix a small problem. The file is XML, so each node is one outline element with your label in a text attribute, and the children are nested inside it. Edit a copy rather than the original, and keep the [layer:N] tag at the end of any label that sits on a deeper layer.

This guide is part of the export and import collection. For the wider product tour, read the complete Canvasola guide, and keep the keyboard shortcut cheat sheet open while you work.