Most resume guides talk about formats in the abstract: chronological, functional, hybrid. The choice that actually matters earlier is the format of the file itself and the layout choices inside it. Get those right and the rest is preference.
How an ATS reads your resume
An ATS parses a document into structured fields: contact info, work experience entries, education entries, skills, and so on. The parser is looking for patterns it recognizes. Dates next to job titles. Bullets under each role. Section headers it has seen before. When the parser sees something it does not recognize, it makes a guess. Bad guesses are how a five-year role ends up showing as "duration: 0".
This is why the format conversation has two parts. First, the file format on disk. Second, the layout on the page.
File formats
PDF and DOCX are the two safe choices in 2025. DOCX is the most reliable across legacy ATS, and many older systems still parse it more cleanly than PDF. Modern ATS handle PDF well as long as the PDF was generated from a word processor or a builder rather than scanned or exported from an image.
Avoid: PNG and JPG resumes (no text layer), single-column scans, ODT, RTF, and PDFs that were saved from a slide deck. If you are not sure your PDF has a text layer, open it in a browser and try to select a sentence with your mouse. If the text does not highlight, the parser will not read it either.
The layout choices that break parsing
A clean ATS-friendly layout has fewer surprises than the average designer template. The patterns that confuse parsers are well known.
Two-column layouts. A sidebar with skills on the left and experience on the right looks tidy to a human and reads like word salad to many parsers. Stick to a single column for the main flow.
Tables. Even invisible tables. Some parsers read tables row by row across columns, which scrambles the content. Use a normal list under a heading instead.
Text in headers and footers. Email addresses, phone numbers, or links placed inside a Word header often disappear from the parsed output. Put your contact line in the body of the document.
Custom section names. "Career Journey" reads as creative. "Work Experience" gets indexed correctly. Save the personality for the bullets, not the headers.
Images, icons, and graphical bars for skills. Anything pictorial is invisible to the parser. A skills section with a colored bar showing "Python: 85%" parses as "Python".
Once the file is safe, then pick a structure
With the parsing risk out of the way, the chronological structure works for most people. Recruiters read top to bottom, most recent first, and they expect to see dates and job titles in obvious places. A functional structure (skills first, jobs as a list at the bottom) often signals that you are hiding gaps; recruiters do read it that way. The hybrid layout, a short summary at the top followed by chronological roles below, is a fine middle path if you are changing careers or you have a strong portfolio you want to surface.
The honest rule is: write the document so a parser can read it and a tired human can scan it. Choose the layout last, after you know your file format and your headings are boring on purpose.