nomnoml vs SequenceDiagram.org (2026): which should you pick?

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 SequenceDiagram.org if

• Fits if you draw sequence diagrams and want them stored in your own Drive
• Works for people who want diagrams processed in the browser, not on a server

Look elsewhere if

• Skip it if you want a freeform whiteboard: sequence and architecture diagrams only
• Not for you if you need live co-editing, because sharing is by link or saved file
• Watch out: the code is not open source, and the paid on-prem Docker version has no published price
• Too light for team spaces: there are no accounts or shared workspaces listed

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.

SequenceDiagram.org

• It covers sequence and architecture diagrams only, not freeform whiteboarding.
• The code is not available under an open-source license.
• There is no real-time multi-user editing; sharing is by link or saved file.
• The on-prem Docker version is a paid perpetual license, but its price is not published.

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.

SequenceDiagram.org

Text and drag-and-drop together

A diagram is described in a text script and can also be edited by clicking and dragging on the drawing.

Client-side processing

All parsing, processing and drawing happens in the browser, which the site says means diagram data is not transferred over the internet.

Saving and sharing

Diagrams save to a file, Google Drive, OneDrive or browser storage, and a share link can be generated.

Export

Export as SVG with the source text embedded, or as PNG; PDF is produced by printing from the browser.

Architecture diagrams

Besides sequence diagrams the editor can create architecture diagrams, which need a recent Chrome, Edge, Firefox or Safari.

Plugins and on-prem

Plugins exist for Confluence Cloud and IntelliJ IDEA, and a Docker image is offered for internal company use.

nomnoml

• Free$0

  The whole editor, the npm library and the command-line renderer are free under the MIT license.

SequenceDiagram.org

• Web app$0

  The browser editor is free to use; the site invites voluntary Patreon support from $1 a month.