Dia and diagrams.net (formerly draw.io) are the two most popular free diagramming tools — and they take opposite approaches. Dia is a classic offline desktop application; diagrams.net is a modern tool that runs in your browser (with an optional desktop app). Both cost nothing. So which free tool should you actually use?
Dia vs diagrams.net at a Glance
| Dia (v0.97.2) | diagrams.net (draw.io) | |
|---|---|---|
| Price | Free, GPL open source. No limits. | Free. No meaningful limits, no account required. |
| Where it runs | Desktop: Windows, macOS (via XQuartz), Linux. | Browser (any OS) + optional desktop app. |
| Works offline | Yes, fully. | Yes — desktop app works offline; browser version can too once loaded. |
| Installation | Download and install (~20 MB). Get Dia here. | None needed — open the site and draw. Desktop app optional. |
| Account required | No. | No. |
| Interface age | Dated (early-2000s GTK look), but functional. | Modern, actively developed. |
| Shape libraries | Deep technical sets: UML 2.x, ERD, network/Cisco-style, electrical, plus community packs. | Very broad: software, network (AWS/Azure/GCP icons), business, BPMN, and more. |
| Storage | Local .dia files. | Your choice: device, Google Drive, OneDrive, Dropbox, GitHub. |
| Best for | Offline-first users, Linux users, lovers of classic desktop software. | Anyone who wants zero-install diagramming, modern UI, cloud storage options. |
Two Philosophies of “Free”
Dia represents the old-school free software model: a program you install, that runs entirely on your computer, released under the GPL so it can never be taken away or paywalled. It asks for nothing — no account, no email, no telemetry — and in return it looks like software from 2005, because in many ways it is. That is not a criticism so much as a description: Dia does a defined job reliably and never changes the deal.
diagrams.net represents the modern free model: a web application (open-source itself, notably) that you simply open in a browser. No install, no admin rights needed — which matters enormously on locked-down work or school computers. You can save to your device or connect Google Drive/OneDrive/Dropbox/GitHub. It’s free without the asterisks that usually accompany “free” online tools.
Because both are genuinely free, this comparison is refreshingly free of sales pressure: pick whichever fits how you work.
Getting Started: Zero Friction vs One Install
diagrams.net’s killer feature is the absence of setup. Need a quick flowchart in a meeting? Open the site, draw, export PNG, done — nothing installed, nothing to explain to IT. Dia requires a download and install (straightforward on Windows and Linux; Mac users need XQuartz first — see Dia for Mac). If you diagram on machines you don’t control, diagrams.net wins this round without contest.
Where Dia claws back ground is the offline-by-default experience. Once installed, Dia launches instantly, never waits on network, and works identically on a plane, in a datacenter basement, or on an air-gapped lab machine. diagrams.net’s desktop app covers much of this too, but Dia’s two decades of offline-desktop refinement show in small ways — keyboard-driven workflows, instant startup, tiny resource footprint (~20 MB installed).
Shape Libraries and Diagram Types
Both tools cover the core diagram types well: flowcharts, UML, network diagrams, ERDs, org charts. Dia’s particular strengths are its mature technical stencils — the UML 2.x set, ERD shapes, Cisco-style network icons (walked through in our network diagram tutorial), and electrical symbols — plus installable community shape packs (custom shapes guide).
diagrams.net’s library is broader in the modern directions: current AWS/Azure/GCP architecture icons, Kubernetes shapes, and business-process templates that Dia’s 2011-era set doesn’t include. If you draw cloud architecture diagrams with vendor-specific icons, diagrams.net is the more practical choice. If you draw classic UML, flowcharts, and network topologies, Dia’s library is every bit as capable.
Look, Feel, and Output Polish
Honesty requires saying it plainly: Dia looks old. The GTK interface, default fonts, and styling belong to another era. The diagrams it produces are perfectly legible and professional for engineering documentation, but making them beautiful takes manual effort — our export guide shows how to get crisp SVG/PNG output.
diagrams.net looks like a current product and its default styles need less tweaking before a diagram goes into a presentation. If the visual polish of your output matters and you’d rather not fiddle with styling, diagrams.net saves you time on every diagram.
Privacy and Data Control
Both tools respect you more than the average cloud app. Dia never sends anything anywhere — there is no network code for telemetry at all. diagrams.net processes your diagrams locally in the browser by default and doesn’t require an account; connecting cloud storage is your choice, not a requirement. For most threat models these are equivalent. For the strictest environments (no browser-based tools allowed, period), Dia’s pure-desktop nature is the safer documented choice.
A Concrete Task in Both Tools: Diagramming a Home Network
Abstract comparisons only go so far, so here’s the same job done both ways: documenting a home network (router, switch, NAS, two PCs, a printer, and the ISP connection). In Dia: install once, open the network sheet, drag Cisco-style router/switch icons onto the canvas, connect with orthogonal lines, label each link with its speed, export SVG for your documentation folder. Total time after install: about fifteen minutes, and the result is a clean, precise technical diagram. The icons look professional, the connectors stay glued to shapes when you rearrange, and the file sits in your docs folder forever.
In diagrams.net: open the browser, search the shape library for the same device icons (including current vendor-specific ones Dia lacks), drag, connect, and save to Google Drive or download the .drawio file. Same fifteen minutes, zero install. The output looks slightly more modern with less styling effort, and sharing is a link instead of a file attachment. The diagrams are equivalent in quality; the workflows differ only in where the tool lives and where the file goes. This is representative: for bread-and-butter technical diagrams, the tools are interchangeable, and your choice should follow your environment (locked-down machine? offline lab?) rather than the feature list.
For Classrooms and Computer Labs
Teachers and lab administrators ask about these two tools a lot, so here’s the direct guidance. If you manage a lab of machines you control, Dia is the easier deployment: a tiny installer, no accounts for students to create, no browser dependency, identical behavior on every machine, and .dia files students can submit like any assignment file. It also teaches the discipline of file-based work — saving, naming, backing up — which is pedagogically useful.
If students work on their own devices (especially Chromebooks or tablets), diagrams.net is the pragmatic choice: nothing to install, works in any browser, and students can start diagramming in the first minute of class. For UML coursework specifically, both are fine — Dia’s UML stencils are slightly more notation-complete (see our UML tutorial), while diagrams.net’s sharing makes peer review easier. Many instructors standardize on one and accept the other; since both are free, there’s no budget meeting required either way.
Which Should You Choose?
- Choose Dia if: you want a classic offline desktop tool, you’re on Linux, you love keyboard-driven workflows, or you need the mature UML/ERD/network stencil sets with zero setup after install. Download Dia free here.
- Choose diagrams.net if: you want zero-install diagramming, a modern interface, current cloud-architecture icons, or you work on locked-down machines. Open it in your browser — no account needed.
- Use both if: you’re pragmatic. Many engineers keep Dia for offline technical work and use diagrams.net when collaborating or when they need modern cloud icons. They cost the same (nothing), so there’s no reason not to.
Want something more polished — for free or paid?
Both tools above are free, so there’s nothing to buy here. But if you’ve outgrown free tools and want a modern paid desktop diagrammer with a large template library and support, EdrawMax is the natural next step up. Prefer online collaboration? Compare with Creately.
Frequently Asked Questions
Is diagrams.net really free? What’s the catch?
It’s genuinely free — the core application is open source, no account is required, and there are no meaningful feature limits. Revenue comes from related commercial products (like integrations), not from paywalling the diagrammer.
Can diagrams.net work offline?
Yes. The desktop app works fully offline, and the browser version can work offline once loaded. Dia remains the simpler guarantee of offline operation since it has no web component at all.
Which is better for UML diagrams?
Both are capable. Dia’s UML stencils are mature and its offline workflow suits focused modeling work (see our UML class diagram tutorial). diagrams.net’s UML shapes look more modern and its sharing is easier. Try both — they’re free.
Can I open Dia files in diagrams.net or vice versa?
Not directly — they use different native formats (.dia vs .drawio). Exchange via standard exports: Dia exports SVG/PNG/EPS, and diagrams.net imports a wide range of formats including SVG. For editable exchange, pick one tool per project.
Is draw.io the same as diagrams.net?
Yes. draw.io was renamed to diagrams.net; it’s the same project and the same free tool.
How does Dia compare to paid tools instead?
See our Dia vs Microsoft Visio and Dia vs Lucidchart comparisons for the paid side of the market.
Related comparisons: Dia vs Visio · Dia vs Lucidchart · Dia vs yEd