Herb on Rails
ERB does not know that it is generating HTML. It finds the <% %> tags, evaluates the Ruby inside them, and concatenates everything else as plain text. Whether the result is valid markup has never been its problem.
Herb changes that. On August 25, 2026, the Ruby on Rails core team merged Add Herb as an HTML-aware ERB implementation, which brings in Herb, an ERB implementation that parses HTML and ERB into a single syntax tree and uses Prism for the Ruby inside the tags. Broken markup can now fail while the template compiles, instead of reaching a browser.
In this article, you will learn what Herb is, how to audit your own views with it today, what it can fix for you, what it cannot, and…









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