A functional resume groups your experience by skill category (e.g., "Leadership," "Data Analysis," "Project Management") rather than by job and date. Work history is demoted to a short list at the bottom or omitted entirely.
The appeal is obvious: it de-emphasizes employment gaps, short tenures, or a non-linear career. The problem is that recruiters know this, and many view functional resumes as a red flag that something is being hidden. ATS parsers also tend to struggle with the skill-category layout since it doesn't match the expected role-date-company pattern.
If your situation genuinely requires a skills-forward presentation — a career change, a return from a long gap, or a pivot with very different prior experience — use a combination format instead. It gives you the skills-first opening while preserving the familiar chronological experience list that recruiters and ATS expect.