Checklists for software errors, setup, and tool workflows.

1. Reproduce

2. Isolate

3. Apply

4. Verify

Latest checklists

When cloning or pulling from a Git repository, you may see:

fatal: unable to access...

Fix 'Python Command Not Found' After Windows Installation
You installed Python on Windows, but when you type python in Command Prompt, you get...

How to Downgrade Node.js for Package Compatibility
You install a package and get errors like requires Node.js >= 16, but you have 18...

Fix npm install Incompatible Node Version Errors
When you run npm install and get an error about an incompatible Node.js version, it ...

Cloudflare 521 Error: Troubleshooting and Fixes
When you see a 521 Web Server Is Down error, it means Cloudflare cannot establis...

Fix Git 'index.lock file exists' Error
If you see fatal: Unable to create 'path/.git/index.lock': File exists. when...