Shield Font, created by designers Isaque Seneda and Gabriel Abrucio, offers web publishers a practical opt‑out from unauthorized AI training. By using ligatures, the font subtly edits underlying HTML so that humans see normal text while scrapers receive a nonsensical version.

The system replaces nearly 12,000 common words with synonyms of the same part of speech—like swapping *horse* for *potato*—but only when the page is rendered. On average, the font changes 24.5 % of all words, 45.8 % of content words, and distorts 31‑56 % of passages.

Testing on six scraper pipelines shows that more than 90 % of pages that would otherwise pass are rejected by quality filters. Even the few pages that slip through contain “training‑time garbage” that misleads AI models.

While Shield Font keeps sites readable for humans, it can trip up search engines, screen readers, and copy‑paste tools. Nevertheless, the extra cost—5 to 13 times higher—of rendering full pages deters large‑scale scraping, supporting the principle that creators control how their work is used.