Definition
Plain language
A free online library of old books whose copyrights have expired.
As stated in the literature
A public-domain digital text corpus, often used as a source of pre-modern prose for training or evaluation.
Why it matters: It offers a large, freely usable pool of older writing that researchers can draw on without copyright barriers.
For example, you can download the full text of a classic 19th-century novel from it for free because its copyright has long expired.
Heard on the show
“Get real pre-1923 books — about a thousand passages of actual old prose from Project Gutenberg — and mix them into the human side of the detector's training.”Episode 220 — Write Like It's 1923: The One-Prompt Trick That Beats AI Detectors