A prompt library is a collection of templates you fill in manually. Existence Compiler crawls your live URL and produces the output automatically. The gap between them is the amount of work you have to do yourself.
A prompt library gives you a template such as: "Write meta tags for a [product type] that does [X] for [audience]." You fill in the blanks, paste it into ChatGPT or Claude, read the output, copy it, and implement it manually.
This requires you to know which prompts exist, which ones apply to your situation, and how to evaluate the quality of the output. There is no audit of your live page, no score, and no gap detection — you do not know what is missing until you run each prompt individually.
Paste your URL. The system crawls the live page, identifies every missing signal across five dimensions, and produces a structured Fix Pack with ready-to-paste code. No prompts to write. No blanks to fill. No manual gap detection.
Prompt library
Existence Compiler
Prompt libraries are useful when you want to generate original content — ad copy, blog posts, social posts, or product descriptions. They are not designed for technical audits or gap detection. They complement each other: Existence Compiler identifies what to fix, a prompt library helps you refine the copy once you know what is needed.
Scan any public URL and discover if humans, search engines, and AI agents understand what your project does.