DIA File

What are DIA files and how to open them

Are you having problems opening a DIA file or are you simply curious about its contents? We're here to explain the properties of these files and provide you with software that can open or handle your DIA files.

What is a DIA file?

DIA files have multiple uses, and Dia Drawing is one of them. Read more about the other uses further down the page.

Dia Drawing

.dia files are the drawing files created by using Dia. Dia is an open-source drawing program that is used to create structured diagrams on your computer.

Dia can draw different shapes for use in flowcharts, circuit diagrams, network diagrams, and more. The files saved when you use Dia contain the .dia extension. Dia was originally developed by Alexander Larsson in 1998.

How to open DIA files

We have identified one DIA opener that is compatible with this specific type of DIA file.

Programs that open Dia Drawing files

Last updated: October 27, 2026

All known file formats using extension .DIA

While Dia Drawing is a popular type of DIA-file, we know of 6 different uses of the .DIA file extension. Different software may use files with the same extension for different types of data.

Diagram-Master Diagram

Diagram-Master Diagram format stores diagrams created by the Diagram-Master program by Decision Resources (later Ashton-Tate), used in the mid-1980s on DOS to make organization charts and Gantt (project timeline) charts with high-quality presentation graphics.

These files are produced by Diagram-Master when a user saves or exports their work; they include all diagram elements such as chart structures, boxes, connections or bars in a Gantt chart, and any associated layout or style settings entered in the program. These diagrams were intended for display, printing, or plotting using devices supported at that time (CGA, EGA, IBM Professional Display, laser printers, plotters).

A distinguishing technical feature is that Diagram-Master Diagram files begin with the ASCII string "COMMENT" at offset 0x0, contain textual markers including "1000" and "END" within their contents.

While we have not verified the apps ourselves yet, our users have suggested three different DIA openers which you will find listed below.

Diagram! Diagram

Diagram! Diagram files store technical and business diagrams created by the Diagram! application made by Lighthouse Design for the NeXTSTEP operating system. They are used to build structured illustrations such as flow‐charts, entity-relationship diagrams, PERT charts, and general information graphics. Diagram! offers smart linking of graphical objects, labels that stay attached when objects move, import of data from other NeXTSTEP applications, drag-and-drop insertion of images or spreadsheets, and voice annotation, so diagrams become interactive, maintainable, and integrated rather than static artwork.

These files are authored by Diagram! and persist in its native diagram format. When opened again in Diagram!, the diagram structure - including shapes, connections, text, layout, rotations, palettes, and linked resources - is reconstructed. The file format was documented by its developer and described in publicity materials around version 2.0, which introduced rotation, more intelligent line labels, customizable palettes and a "parsable file format" so that developers could access and manipulate the internal view of diagrams.

Internally the format is a NeXTSTEP "typed stream": a serialization of Objective-C objects preserved with their class identity, relationships and instance variables. File contents begin with a header identifying a typedstream, followed by object data referring to collection classes like LIGHTORDEREDCOLLECTION, LIGHTCOLLECTION, sets or ordered sets, graphic classes like SOLIDGRAPHIC, SPLINEGRAPHIC, and attribute objects like RECTANGLE, EDITVIEW, VIEWGRID, PRINTINFO, and various font and text classes. Such byte signatures and embedded strings are characteristic among Diagram! files.

Diagraph Graphics

Diagraph Graphics is a vintage graphics format created by Computer Support Corporation in the early 1980s for DOS and HP-150 systems for building diagrams, symbol-based charts (line, bar, pie), and clip-art style graphics. It stores drawings produced by the Diagraph application so they can be reloaded or printed later.

Files in this format are binary image/diagram files saved by Diagraph version 3.x. They combine internal graphical objects (symbols, shapes, arcs etc.) with styling (color or monochrome, layout) rather than being simple bitmaps. Users work inside Diagraph to compose the diagram, and when the work is saved, Diagraph writes a .DIA graphics file; the format is read back only by Diagraph itself. Diagram elements are usually arranged like clip art, with libraries of symbols (symbol libraries), charts, and pictorial elements included in the drawing canvas.

Files begin with a distinctive header in ASCII that identifies Diagraph version 3, specifically the text "DIAGRAPHV3." Some files also include the string "PALETT2" which relates to embedded palette or color table data. These signatures appear at known offsets (for example "DIAGRAPHV3." at offset 0), so software seeking to recognize this file type can test for them.

Graph Diagram

.dia files are graph diagram files created using Dia, a drawing software licensed free for users. Dia is used in creating graphs, circuit and network diagrams, and more. The saved files users create using Dia are saved with the .dia extension.

Dia was developed in 1998 by Alexander Larsson.

PolyPlot Diagram Definition

We know that one DIA format is PolyPlot Diagram Definition. We have not yet analyzed in detail what these files contain and what they are used for. We're working on it.

Various apps that use files with this extension

These apps are known to open certain types of DIA files. Remember, different programs may use DIA files for different purposes, so you may need to try out a few of them to be able to open your specific file.

Help us help others

File.org helps thousands of users every day, and we would love to hear from you if you have additional information about DIA file formats, example files, or compatible programs. Please use the links below or email us at submit@file.org to discuss further.