Screen scraping
Extracting data from an interface built for eyes rather than programs — always a workaround, often a permanent one.
The term comes from the mainframe era, when integrating with a system that had no API meant emulating a 3270 terminal, reading the characters at columns 12 through 34 of row seven, and interpreting them. The technique survived the move to the web essentially unchanged: fetch the HTML, locate the right element, take the text. Tools like Beautiful Soup, Scrapy and Puppeteer make the mechanics trivial.
The fragility is structural. The interface is designed for humans and may change at any time, so a moved div or a new login flow breaks the scraper without warning. The legal position is unsettled and varies by jurisdiction, and robots.txt is a courtesy, not a control. A real API is always preferable, where one exists.