ATS-friendly does not mean plain. It means the text is extractable in the right order. You can keep colour, hierarchy, and typography — you just cannot hide content inside layout.
Safe: single column, standard section headers, real text, one font family with weight contrast, bullets as bullets, and colour used on headings rather than as blocks behind text.
Unsafe: two-column layouts with sidebars, tables for alignment, text boxes, content in headers and footers, icons replacing labels, and anything rasterised into an image.
File format: PDF unless the application asks for .docx. Export from a tool that embeds selectable text — if you cannot select your name in a PDF reader, neither can the parser.
Naming: FirstName-LastName-Role.pdf. It survives download folders and shows up correctly in recruiter systems.
Test it the lazy way: copy all the text out of your PDF and paste it into a plain notepad. If the order is scrambled or sections vanish, that is what the ATS sees.