If one person left tomorrow, which folders would nobody understand?

Paid tools such as CodeScene and Hercules answer this from your repository history. This page does the core of it for free: paste a git log and get a recency-weighted bus factor for every folder, with orphaned folders (the main contributor has gone quiet) and single-owner folders (one active person, no backup) listed first, and who to pair with.

Nothing is uploaded. The log you paste is read in this browser and never leaves your device, and this tool makes no network calls of its own. It is a heuristic from commit history, not a measure of who understands the code.

1. Export your history

Run this inside your own repository and paste everything it prints:

git log --no-merges --since=2.years --format='@@|%an|%ae|%at' --numstat

It lists author names, emails, commit times and changed file paths, so scan it before sharing it with anyone. Here it stays on your device.

2. Paste it

Paste a git log above and click Analyse.

Prefer a CLI, or want this in your own CI?

Same logic, zero dependencies, one file. It runs git log on your machine and nothing else:

python3 busfactor.py                        # analyse the repo in the current directory
python3 busfactor.py path/to/repo --depth 3  # folders three levels deep
python3 busfactor.py --format json           # machine-readable
python3 busfactor.py --fail-on-orphaned      # exit 2 if a folder lost its owner

Get busfactor.py from the repo — stdlib only, nothing to install, no network calls. Options: --since, --half-life, --inactive-days, --min-commits.

Common questions

What is a bus factor?

The bus factor, or truck factor, is the smallest number of people who would have to leave a project before it stalls because nobody left knows the code. A bus factor of 1 means a single departure is enough. This tool computes it per folder as the fewest contributors whose recency-weighted changes add up to half of the folder's total.

How is ownership calculated here?

Each commit adds the lines it added and deleted in a folder, capped at 500 per file so one giant change cannot own a folder, and halves in weight every 180 days so recent work counts for more. Bots, lock files and vendored or minified files are ignored. The folder's bus factor is how many top contributors it takes to reach half the total.

What do orphaned and single-owner mean?

Orphaned means the person with the largest share of a folder has made no commit anywhere in the last 90 days, so the folder's main knowledge holder may be gone. Single-owner means one still-active person holds at least 80 percent of a folder, so it has no real backup yet. The report names the most active other contributor to pair with.

Does this tool send my git history anywhere?

No. It makes no network calls at all. The log you paste is analysed in this page and never leaves your device; the CLI only runs git log on your own machine.

Does a high bus factor mean my team understands the code?

No. This is a heuristic from commit history, not a measure of who understands the code. Reviewers, pair programmers, documentation, squashed commits, shared accounts and people who left the company under another email all change the real answer. Treat it as a prompt for a conversation, not a verdict about any person.

More: what is a bus factor, and how do you raise it?