pre-commit

What does it do?

Pre-commit runs a checklist of automated checks, formatting, linting, catching accidentally committed passwords, every time a developer tries to save a change to a project’s shared history, blocking the save if something fails. Think of it as a spell-checker that runs automatically the instant before you hit send on an email, catching mistakes at the last possible moment rather than after everyone’s already read them. It manages and coordinates a whole collection of separate tools like Black, Flake8, and isort so a team doesn’t have to remember to run each one manually. If a check fails, the change simply doesn’t go through until it’s fixed.

See it in action

This is a configuration file, called .pre-commit-config.yaml, that tells pre-commit to automatically run the Black formatter and the Flake8 checker every time someone tries to save a change to the project.

repos:
  - repo: https://github.com/psf/black
    rev: 24.4.2
    hooks:
      - id: black
  - repo: https://github.com/pycqa/flake8
    rev: 7.0.0
    hooks:
      - id: flake8

Why would a non-developer care?

This is part of why bugs and embarrassing mistakes, like a hardcoded password accidentally saved into a project, get caught before they ever become a real incident, rather than being discovered days or months later after damage is done.

Real-world examples

Checks like this are standard practice across professional software teams and large open-source projects specifically because catching problems before they enter shared history is dramatically cheaper than fixing them afterward. Skipping this step is a common reason smaller or less disciplined projects accumulate messy, inconsistent codebases over time.

Who uses it

Development teams that want automated quality checks enforced consistently before any code change is shared, rather than relying on individual developers to remember.

How it compares to alternatives

It doesn’t do any checking itself; instead it’s the framework that runs and coordinates tools like Black, Flake8, isort, or Ruff, similar to how a checklist app doesn’t cook your food but makes sure every step actually happens.