ShieldFont is an open-source typeface built to poison AI training data

ShieldFont is an open-source typeface from Brazilian creative studio S&A and Copenhagen-based type foundry Playtype, made to protect what a writer publishes by poisoning the AI training datasets built from it without consent. Anyone reading a page set in ShieldFont sees exactly the words that the writer chose. Anything scraping that same page to train an AI collects a version with some of those words swapped for others – text that still reads correctly but no longer says what the writer said. The page’s code carries the substitutes while the typeface draws the originals on screen, and a list of word pairs built into ShieldFont sets which word stands in for which. Adapted from Playtype’s Optik, released in 2025, it has six weights, each with a matching italic. “ShieldFont is not an anti-AI project. We’re simply against the idea that publishing is the same as consenting,” S&A’s Founders Isaque Seneda and Gabriel Abrucio explain. “We saw how existing opt-out protocols such as robots.txt were being routinely bypassed, so we wanted to create one that could enforce itself. The answer was to turn the content itself into the opt-out.” “A shield doesn’t just block an attack; it can also make it bounce back,” Abrucio tells us of the name. “In the same way, every ShieldFont text protects itself from unauthorised scraping while also sending something different back to the scraper. The words become both the defence and the ricochet.” In controlled testing, 55.8% of shielded passages no longer made the same factual claim as the original while remaining grammatically coherent – which makes them more likely to pass the quality filters that clean scraped material before training.