R Markdown is an easy-to-learn tool for reproducible research. Many people, however, bump into problems using YAML, the language that specifies metadata for R Markdown documents. ymlthis makes it easy to write valid YAML by handling the syntax and documenting the majority of YAML fields in one place. ymlthis will help you write metadata for R Markdown, bookdown, blogdown, and more. Let the Shiny add-in create a new R Markdown file for you or work with YAML and R Markdown files directly. ymlthis finally gives you a workflow that is better than trying to find and paste the YAML from the last R Markdown document you used.