One-off tools built by one person for one specific need.
The economics of building software changed. It no longer has to serve lots of people to be worth building.
Idea at 9 a.m. -> useful tool by lunch.
For example:
Turn raw regression output into a polished LaTeX table
Generate practice exams from your lecture slides
Summarize and tag 200 papers for a literature review
Convert a dataset between formats (Stata → R → Python)
Build a custom grading rubric from your syllabus
This website!