FlowDoc — Lightweight diagram docs

A free, open-source ProcessOn alternative for developers tired of diagram quotas

Problem

Developers still need flowcharts and sequence diagrams when writing design docs, but the common tool ProcessOn caps free diagrams by quantity, and users openly ask in the community for alternatives. There is also precedent for pure local tools, showing high acceptance for local, account-free, unlimited document tools.

Solution

An in-browser flowchart and sequence diagram editor supporting both Mermaid text and drag-and-drop, exporting PNG/SVG/Markdown, with docs and diagrams stored locally or in the user's own Git repo. Share links embed into design docs without requiring an account or limiting diagram count.

Users

Software engineers, tech leads, and indie developers who write design documents

MVP

Bidirectional Mermaid text and drag-and-drop editing; basic flowchart, sequence, and state diagram templates; export to PNG/SVG/Markdown; local storage with optional Git sync; login-free share links

Revenue

Open-source core with paid hosted sync and team spaces; or a one-time desktop license

Why now

Developers are increasingly tired of subscriptions and quotas, local-first document tools spread naturally in tech communities, and an indie developer can start with open source plus light hosting