Methodology and Sources

How we pick topics, choose sources and keep entries current.

Last updated: October 30, 2026

How we pick topics

The library has five areas of nine entries. We choose topics that a beginner meets early and that stay true over time. We skip topics that are mostly about one product version, because those age fast.

Source ranking

When sources disagree, we trust them in this order:

Order	Kind of source	Examples
1	Standards and specifications	IETF RFCs, W3C and WHATWG specifications
2	Government and public-body guidance	NIST, CISA, the U.S. Bureau of Labor Statistics
3	Official product and language documentation	MDN Web Docs, the Python documentation, PostgreSQL manual
4	Respected textbooks and course material	University course notes and open textbooks

We do not use forum posts, anonymous blogs or social media as the only source for a fact.

How we check facts

Each factual claim must match at least one source from the list above.
Code and command examples are kept simple and must be correct for the idea they show.
Every source link opens the official page. If a link breaks and we cannot find a replacement, we remove the claim it supported.

Data and statistics

We publish a number only when an official source provides it. The entry names the source, the year or date of the data, and what the number measures. We do not round up, estimate or combine figures to make a point.

Levels and types

Each entry has a level (beginner or intermediate) and a type (concept, skill or career). These labels help you filter the library. They describe the writing, not a promise about what you will be able to do afterward.

Keeping entries current

Each entry shows its last update date. We review entries on a regular schedule and sooner when a source changes or a reader reports a problem. Changes that fix an error are listed on the corrections page.

Limits

An introductory library cannot replace practice, formal training or professional advice. Read the disclaimer for details.