Guides
What is an FML file?
If you draw floor plans for clients in the Netherlands, sooner or later someone asks for "the FML". Funda needs it, Floorplanner produces it, most other tools do not. This guide explains what an FML file is, what is inside, who asks for it, how to open, make and convert one, and the pitfalls when you move it between tools. Dinoplan is our own product and reads and writes FML; we mention it where relevant.
FML in short
FML stands for Floorplan Markup Language, a file format that stores a floor plan as data rather than as a picture. Floorplanner, a company from Rotterdam in the Netherlands, created it for its own drawing tool; per the specification it dates from 2004, the whole Floorplanner platform runs on it, and the current version is 3.0.
An FML file is plain text. Despite the word "markup" in the name, the current format is structured as JSON, a common way to organise data that software can read, change and rebuild. That is the difference from a PNG or PDF: an FML file knows that a line is a wall with a thickness and a height.
What is inside an FML file
An FML file describes a building as a list of parts with coordinates and sizes, organised in layers:
| Part | What it describes |
|---|---|
| Project | Name, description and settings for the whole drawing, such as metric or imperial units, dimension lines on or off and the rotation of the north arrow. |
| Floors | Each storey separately, with a level (0 is the ground floor) and a height in centimetres. |
| Designs | One or more layout variants per floor. |
| Walls | Start and end point, thickness and height. Doors and windows are openings in a wall. |
| Areas | A room: a polygon of points with a name and a colour. |
| Items | Furniture and other objects, with position, size and rotation. |
| Labels, dimensions and lines | Texts, custom dimension lines and loose lines. |
A floor can also hold a link to a background image to trace over, and camera positions for 3D. Not in the format: roofs and roof shapes, garden elements, electrics and plumbing.
Want to try it? Open the sample home, no account needed.Want to try it on your computer? Email yourself the link.
Who asks for an FML file
Dutch real estate agents, for Funda
Interactive floor plans on Funda, the Dutch property portal, come from FML files. The agent adds or replaces the plan in Funda Desk, their back office, by uploading an .fml file. If you draw for Dutch clients, this is why they ask. Our guide on floor plans for Dutch real estate covers the rest of what they expect.
Anyone moving a plan between tools
Because the format is openly documented, other programs can read and write it, so a plan drawn in one tool can be edited in another. Floorplanner also offers an API. In practice FML is the closest thing to an exchange format for real estate floor plans.
How to open an FML file
- In a drawing tool. Floorplanner opens its own files. Other tools that support FML can import it. In Dinoplan, choose import and select the
.fmlfile; walls, doors, windows, rooms, floors, measurements and texts are read in. - In a text editor. Any editor (Notepad, TextEdit, VS Code) opens it. You see raw data, coordinates, sizes and names, not a drawing. Useful to check which floors or room names are in the file.
Do not edit an FML file by hand in a text editor. One wrong comma or bracket can make the whole file unreadable for every tool.
How to make an FML file
You need a tool that exports FML. In Floorplanner it is the native format. In Dinoplan, draw the plan or import it from a PDF, DXF or sketch, then export to FML. FML export is part of a paid project (€2.99 per project, then unlimited exports for that home) and of Pro (€19.99 a month, €16.99 billed yearly); the free plan has no FML. Most CAD and general design tools do not export FML, which is why drafters with Dutch clients end up with a tool that does.
How to convert FML to PNG, PDF or SVG
There is no stand-alone converter. Open the FML in a tool that reads it, then export:
- Import the FML file in Dinoplan (or open it in Floorplanner).
- Check one known measurement, for example a door width.
- Pick the client's house style, if you have one.
- Export as PNG (up to 8000 pixels in paid plans), JPG, SVG or PDF with address and area table.
The other direction, PNG or PDF to FML, is harder because a picture does not contain walls as objects. Dinoplan reads an architect's vector PDF (walls, doors, windows, room names and scale) and traces a scanned or photographed drawing; you then check the sizes and export to FML.
Pitfalls when you exchange FML files
- Unknown furniture. Every tool has its own furniture library. A Floorplanner sofa is referenced by a product code. When you import into another tool, that code may be unknown. Dinoplan maps codes it knows (63 at the time of writing) to its own furniture and shows the rest as a frame of the right size. Expect to redo furnishing when you switch tools, or leave it out; for a listing plan that is often better.
- Scale and units. FML stores sizes in centimetres with a metric or imperial display setting. After import, check one measurement before you export. If the original was drawn roughly, the import is roughly right too.
- Version differences. The documentation describes version 3.0. An old file may hold fields a newer reader ignores, and the other way round. Walls, rooms and openings nearly always survive; decorative details get lost.
- Roofs. FML does not describe roofs. An attic exports its walls and rooms, but the roof shape has no place in the file.
- The licence line. Floorplanner publishes FML under its own licence, the FML License Notice (version 1, 2024). A plan made with the standard must contain a fixed sentence stating that it was created using the FML Standard. Good software adds it automatically; developers should read the full licence.
How Dinoplan handles FML
Dinoplan imports FML from Floorplanner, so you can continue a plan a client started or move your archive over, and exports FML for Funda next to PNG, JPG, SVG and PDF, in a client's house style. The furniture library is basic and there are no photorealistic renders; if those matter, Floorplanner is the stronger choice. The differences are on Dinoplan vs Floorplanner, all functions on the features page and the plans on pricing.
Have an FML file on your computer? Start for free and import it to see how it comes through.
Frequently asked questions
Is an FML file the same as a PDF of a floor plan?
No. A PDF is a fixed document or image. An FML file holds the parts of the drawing, such as walls, rooms and objects, so the plan can still be edited and measured.
Can I upload an FML file to Funda myself?
No. The agent uploads it in Funda Desk. You deliver the file to the agent or the photographer.
Is FML really JSON? The name says markup language.
The name dates from the format's start in 2004. The current specification, version 3.0, describes a JSON structure. When you open a file in a text editor you will see curly brackets and quoted field names.
Do I need to do anything about the licence if I only draw plans?
No. The licence asks for a fixed sentence in files made with the standard, and the software that writes the file takes care of that.