nomnoml vs Swimlanes.io (2026): which should you pick?
As of Nov 13, 2026, nomnoml and Swimlanes.io share a 2.8 GPA, both are free, so the choice depends on which features you need.
Checked Nov 13, 2026 · graded Nov 13, 2026 by ToolGPA
They get the same grade on all five counts.
Price, platforms and features side by side. The table says where each price was read and when.
Which one is for you
Pick nomnoml if
- Fits if you want a class or flow diagram out of a few lines of text
- Works for developers who embed diagrams through the library or command line
Look elsewhere if
- Skip it if you want a freehand canvas or sticky-note board
- Watch out: saving relies on browser localStorage, which the author says comes with no guarantees
- Not for you if you need accounts, sharing links or real-time editing, as the web app has none
- Too light for teams: no collaboration of any kind is listed
Pick Swimlanes.io if
- Fits if you write a sequence diagram a week and want it from text
- Works for explaining an API call or a login flow to someone with a link
Look elsewhere if
- Skip it if you want a freeform canvas or sticky notes: it draws sequence diagrams only
- Watch out: without an account the web address changes on every edit, so an old link shows the old diagram
- Not for you if your company needs a named vendor and published terms, because the site gives neither
- Too light for teams: no real-time collaboration is listed
How we grade them
| 2.8GPAnomnomlGood | 2.8GPASwimlanes.ioGood | |
|---|---|---|
| Value for money | AFree, open source and available as a library and a command line tool as well as the web app. | AFree, with no paid plan listed. It is a web app anyone can open and use, which beats every price in the category. |
| Free plan and trial | AFree outright, with no sign-up, cap or paid plan. | AFree outright: no plan, cap or trial on the page. An account is optional and only collects your diagrams. |
| Features | CClass, component and flow diagrams from text, with styling. It does that fully, but it is a smaller job than a whiteboard, with no freehand canvas or sticky notes. | CDoes sequence diagrams fully, with flow structures, Markdown, sharing and export. That is a smaller job than a whiteboard, with no freeform canvas. |
| Ease of use | CNo store rating on record. You learn its text syntax first. | CNo store rating on record. You write the diagram in a text syntax, so there is a short learning curve. |
| Platforms and integrations | CWeb only for most people, plus a library and command line. No integrations are listed. | CWeb only. Sign-in goes through Google or GitHub, and no apps or integrations are listed. |
| Best for | UML diagrams drawn from a text syntax | quick sequence diagrams in the browser |
The GPA is the average of the five grades: an A is 4 points, an F is none. The full reasons are on each tool's page: nomnoml and Swimlanes.io. How we grade
Price against what you get
nomnoml has no paid plan and scores 2.0 out of 4 on features, ease of use and platforms. Swimlanes.io has no paid plan and scores 2.0.
On this chart the two sit in the same place: the same score for the same starting price. Of the other whiteboard and mind map tools on the chart, none scores higher than nomnoml for less, and none scores higher than Swimlanes.io for less.
Features, ease of use and platforms, averaged
What paid plans start at, a month (each step along is roughly double) →
- The best score at each price
- Has a free plan
- No free plan
Where they differ
- nomnoml is open source, according to its own site.
- Swimlanes.io also covers Markdown and file sharing.
In commonFree planWebDiagrams
At a glance
| nomnoml | Swimlanes.io | |
|---|---|---|
| Pricing | Free | Free |
| Starts at | Free | Free |
| Free plan | None | None |
| Free trial | None listed | None listed |
| Web | ||
| Made by | Daniel Kallin | Swimlanes.io |
| Price read from | nomnoml.com | swimlanes.io |
| Checked | Nov 13, 2026 | Nov 13, 2026 |
Worth knowing
nomnoml
- It draws diagrams from code only; there is no freehand canvas or sticky-note board.
- Saving relies on browser localStorage, which the author says comes with no guarantees.
- The web app has no accounts, sharing or real-time collaboration.
Swimlanes.io
- Without an account, the diagram lives in the URL and the URL changes whenever the diagram is edited.
- It draws sequence diagrams only, with no freeform canvas.
- The site does not name the company behind it or publish terms or a pricing page that we could read.
Key features
nomnoml
- Text syntax with live preview
- Edit the code on the left and the diagram on the right updates as you type, with keyboard shortcuts borrowed from Sublime Text.
- Several UML shape families
- Built-in classifier types cover classes, abstract classes, packages, components, sockets, actors, use cases, states, choices, databases and tables.
- Styling directives
- Directives such as #direction, #fill, #font and #spacing change layout and appearance, and custom classifier styles can be defined and imported from other files.
- Library and command line
- The nomnoml npm package renders diagrams on a web page or to SVG in Node, and npx nomnoml converts a file from the command line.
- Browser-only storage
- The web app is client-side and keeps your diagram in the browser's localStorage, so it is there on your next visit, though the author gives no guarantee.
Swimlanes.io
- Live text editing
- Edit the text on the left and the sequence diagram on the right updates in real time.
- Markdown in messages and notes
- Messages and notes accept italic, bold, strike-through and inline code, plus lists, links, code blocks and Font Awesome icons.
- Flow structures
- The syntax covers conditional sections with if and else, groups, dividers, delays, automatic numbering and actor reordering.
- Sharing and export
- Diagrams can be shared as a link, short URL, image link or embed, or downloaded as an image or PDF.
- Optional account
- Signing in with Google or GitHub collects a person's diagrams in one place; without it the URL carries the diagram.
Plans
nomnoml
Free$0
The whole editor, the npm library and the command-line renderer are free under the MIT license.
Swimlanes.io
Free$0
The site describes itself as a free web app; no paid plan is listed.
Common questions
Which is cheaper, nomnoml or Swimlanes.io?
As of Nov 13, 2026, both nomnoml and Swimlanes.io are free to use.
Which has a free plan, nomnoml or Swimlanes.io?
As of Nov 13, 2026, both nomnoml and Swimlanes.io have a free plan.
More comparisons
How this page was made
- The verdict at the top follows a fixed rule. When both tools are in the same category and either is in our top three for it, the verdict follows that ranking: the higher-placed tool is our pick. The top three weigh who each tool suits as well as its grades, so a pick can go against the GPA. Otherwise the page does not pick one and says which grades higher: the higher GPA first; on a tie, the one with a free plan, then the one that starts cheaper in dollars a month, counted the same way for both; if they are still level, what the choice depends on.
- The grades are our own, from each tool’s review or report card. The GPA is their average.
- Prices, plans and platforms come from each tool’s listing. The table above says where each price was read and when.
- The differences and the answers to the questions are worked out from those listings.