Dia is a free, open-source diagram editor for building flowcharts, UML models, network layouts, and technical drawings. It offers a broad library of ready-made shapes and exports finished diagrams to image, vector, and document formats for documentation, teaching, and design work.
Dia is a free diagram editor that lets you assemble flowcharts, UML models, network layouts, org charts, and database schemas from ready-made shape libraries. You start by picking a sheet of objects, drag the shapes onto a canvas, then connect them with lines that stay attached as boxes move and resize. Text labels, colours, and line styles can be adjusted on each object, while layers, grids, and alignment guides keep larger drawings tidy. Completed diagrams export to PNG, SVG, PDF, EPS, and several CAD and office formats, so the same file can serve a technical report, a slide deck, or a printed handout. The straightforward canvas workflow keeps attention on the drawing itself, not on tool configuration.
Because Dia stores diagrams as structured objects rather than flat pixels, you can reopen a file years later and still edit every box, connector, and label at full quality. The native format keeps shapes resolution-independent, so the same drawing can be re-exported at a different size or format whenever a new deliverable is needed. A built-in scripting interface lets you generate or modify diagrams programmatically, which helps when a repeated pattern must be produced from data. Custom shape sheets can also be defined in XML, letting a team standardise the symbols it uses. Teams that also manage project schedules often pair the editor with ProjectLibre, keeping plans and diagrams in one workflow.
The main benefit of Dia is speed combined with structure: a diagram can be sketched in minutes, yet every element stays editable and precisely placed instead of being flattened into a picture. Shape libraries cover UML, flowcharts, network and circuit layouts, ER models, and many niche notations, so most projects start from symbols that already match the convention rather than from a blank grid. Connectors attach to objects and follow them when layouts change, which removes the tedious re-routing that plagues drawing tools built on static shapes. Layers and grids keep complicated schematics readable, and print scaling means one file can produce both a wall chart and a report figure. Export options span raster images, vector graphics, PDF, and formats used by CAD and office software, so the same diagram can be dropped into documentation, a presentation, or a code repository. Because it is free software with a stable, long-tested editor, small teams gain professional diagramming without subscriptions or per-seat fees.
Dia ships with sheet after sheet of ready-made symbols covering UML, flowcharts, network layouts, entity-relationship models, circuits, SADT, AADL, and similar notations. Switching sheets changes the palette of objects on offer, so a network designer and a software architect can both work in Dia using symbols that match their own conventions.
Objects expose connection points, and lines bound to them follow the shape whenever it moves, resizes, or gets rearranged. Auto-routing adds gaps where lines cross text, arrowheads and dash patterns mark direction and meaning, and labels can sit along the connector instead of in a detached text box.
Each diagram can hold several layers, and any layer can be shown, hidden, printed, or locked independently. That makes it practical to keep background grids, annotation notes, or alternative layouts inside one file and reveal only the parts a given audience should see, rather than maintaining several near-identical copies of the same drawing.
Finished Dia work leaves the editor as PNG, JPEG, SVG, PDF, EPS, DXF, CGM, WMF, or PGF, with resolution and page settings chosen at export time. Vector output keeps curves and text sharp at any print size, raster output suits slides, wikis, and issue trackers, and CAD-oriented formats support mechanical or facility layouts.
A scripting plug-in exposes the diagram model to Python, so objects can be created, queried, adjusted, and rearranged by code. Repetitive jobs such as building a schema-shaped diagram from a data list, standardising fonts across a large file, or exporting a folder of documents become scriptable, which saves time on diagrams that change on a schedule.
Dia reads its own documents plus several foreign formats, including SVG graphics and VDX files produced by Microsoft Visio, letting drawings from elsewhere join an existing canvas. Companion utilities push work further: dia2code turns UML class diagrams into source code, and Parse-Dia-Sql derives database schema statements from entity-relationship models.
New symbols can be built by grouping primitives or described in XML, then collected into a custom sheet that installs alongside the built-in ones. Organisations use this to enforce a house style, so every team member reaches for the same approved icons instead of redrawing them, and the resulting diagrams stay consistent across documents.
A grid with adjustable spacing, snap and alignment guides, zoom levels, and object property dialogs make exact placement straightforward. Step-by-step undo history, clipboard operations, and searchable object palettes round out the canvas editor, so users can refine spacing, colour, and text formatting until a diagram is ready for publication.
No old versions have been added yet.
The editor is built around shape sheets, and the bundled ones cover flowcharts, UML class and sequence diagrams, network and circuit layouts, entity-relationship models, SADT and IDEF blocks, AADL, and other technical notations. Because anyone can author additional sheets in XML, the practical limit is the symbols you can define rather than the ones that ship with the program.
Yes. Dia is free and open-source software released under the GNU General Public License, so there are no licence keys, subscriptions, or per-seat charges. You can also study the source code, adapt it, and share modified builds under the same terms, which makes it a practical option for schools, non-profits, and businesses that prefer to avoid recurring software costs.
Diagrams leave the program as raster images such as PNG and JPEG, as vector graphics in SVG, PDF, EPS, or CGM, and as CAD-oriented output including DXF and WMF. Vector files scale cleanly for print, while PNG or JPEG files drop easily into slide decks, wiki pages, and issue trackers. Export settings for resolution and page layout are chosen when the file is generated.
Dia can import VDX files exported from Visio, along with SVG graphics and its own native documents, so drawings prepared elsewhere can be placed on the same canvas. Complex Visio features, proprietary stencils, and heavily styled text may not translate perfectly, since the two programs model objects differently. It is best to check the imported result and adjust shapes as needed.
A Python plug-in gives scripts access to the diagram model, so objects and their properties can be created, inspected, and modified programmatically. That is useful for generating diagrams from external data, applying consistent formatting across many files, or batch-converting a folder of drawings. Individual objects and the documents themselves are also plain XML, which makes further processing with ordinary tools possible.
Layers let you separate background elements, annotations, and alternative views of the same drawing, and each layer can be hidden, locked, or excluded from printing. A configurable grid with snapping, alignment guides, and zoom controls keeps objects evenly placed, while multiple pages in one document are helpful when a complex system needs to be split into overview and detail sheets.
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