Hello everyone! After my talk at the 2025 Nextflow Summit (you can watch it here: ), I wanted to share the tool that I presented with the community: MetroFlow. What is MetroFlow? MetroFlow is an open source tool that automatically builds an interactive “metro‑map” visualization of Nextflow workflows. The goal is to give developers and users a quick and easy, graphical way to explore and understand workflow structure based on the popular nf-core metro-map style representations, reducing the effort required to write and maintain separate documentation. How does it work? 1. Nextflow Language Server runs on the workflow code to extract the workflow structure. 2. If the language server can’t parse the workflow code, we fall back to the Bioflow‑insight tool (https://doi.org/10.1093/nargab/lqae092) to recover the structure. 3. MetroFlow then represents the workflow structure into an interactive metro‑map that you can explore, edit, and share. Key functionalities • Explore the code ◦ Visualize each process’s code directly from the metro-map representations. ◦ See the conditions which need to be verified for a given path to be taken. • Simplify the graph ◦ Collapse subworkflows into single nodes, reducing the perceived complexity in the workflow. ◦ View subworkflows in isolation. • Edit the layout ◦ Drag nodes to new positions. ◦ Hide or minimize nodes you don’t need. ◦ Highlight specific execution paths. ◦ Export/share a customized layout. These features let you visualize, share, understand, and reuse Nextflow workflows with far less manual documentation, we hope to make the workflow logic clearer for developers, end‑users, and reviewers alike. You can try MetroFlow out here: https://metroflow.pasteur.cloud/ Link to source code: https://gitlab.pasteur.fr/sharefair/metroflow Thanks so much for your feedback. George Marchment

Hi @George Marchment! How do we leave feedback? I don't see any issues section on the metroflow github repository

main_nf.txt

What do you mean @Louis Le Nézet? Which is failing there?

I meant

ch_vcf_tbi

(I've updated the example) This creates loops for the moment. It would also be really nice to have a joint symbol when you perform a combine/join nextflow operation.

Is it possible to run this locally? I don't see the diagram generator in the linked repo, only the visualizer

Hi @James Fellows Yates,

I've also opened issues in the repo, so you can declare it as an issue if you would like

Unfortunately we can't add an issue to https://gitlab.liris.cnrs.fr/sharefair/bioflow-insight without being part of Liris. We can as external user put an issue on https://gitlab.pasteur.fr/sharefair/metroflow but I guess that most of the issue will concern bioflow-insight and not the metroflow server.