Resume parsing is the first thing an ATS does when it receives your application. The parser scans the document, identifies section boundaries, and extracts structured data: contact info, each work experience entry, education, and skills. Recruiters then search and filter against those fields.
Parsing fails for predictable reasons: critical details hidden in headers/footers (many parsers ignore both), tables that scramble column order, text boxes that the parser skips entirely, non-standard section headings ("My Journey" instead of "Experience"), image-based PDFs with no text layer, and multi-column layouts where columns interleave when read top-to-bottom.
To test parsing, copy your resume and paste into a plain-text editor. If the result is coherent — sections in order, dates next to roles, nothing missing — the ATS will likely parse it correctly too.