2 minute read

BloatViz: A Size Visualiser for Binaries

BloatViz helps you understand what actually takes up space in your binaries by turning symbol size data into interactive, zoomable SVG visualisations.

Author: James MW

21st Jan 2026

Categories:

Open Source ESG

We’ve been working on BloatViz, a tool to make it easier to understand where space is actually going in large binaries. Today, we’re announcing its availability for public use in the hope that it’s helpful to others; issues and contributions are welcome 🎉

Get it here

What’s BloatViz?

It takes the output from Google’s famous Bloaty tool and turns it into an interactive SVG treemap that’s aware of namespaces and symbol hierarchy. Rather than a long, flat list of symbols, you get a view that reflects how the binary is structured, which makes it much easier to spot where things have grown or where large chunks are coming from.

The SVG is self-contained and opens in any browser. You can hover to see symbol names and size information, click to zoom into a particular namespace, and run simple regex searches to highlight areas of interest. It’s deliberately minimal — there’s no web service, no UI beyond the SVG itself, and nothing to install beyond the tool.

But why?

Originally developed internally by our incredible intern, Andrew, the motivation came from working with fairly large C, C++ and Rust binaries, where the raw output from Bloaty is accurate but awkward to reason about once you’re dealing with thousands of symbols. Seeing things grouped by namespace makes it immediately obvious which subsystems or dependencies dominate the binary, and it’s been useful for tracking regressions over time.

Under the hood it delegates the hard work to Bloaty. By default, BloatViz statically links it so you don’t need to manage another dependency, though you can also point it at an external bloaty binary if you prefer. It supports the usual Bloaty sources (sections, segments, demangled symbols, etc.) and lets you control how namespaces are split, filtered, and sized.

Recent work on BloatViz came from our intrepid group of engineers who are committed to both open-source software and sharing more of our specialist knowledge and tools with our community.

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