What this actually checks
This is a deterministic parseability check, and deliberately nothing more. It extracts the text from your file the way a parser does, then reports what it found: whether the document is a two-column layout that scrambles in reading order, whether your contact block is machine-readable, whether section headings are recognisable, whether dates parse, and whether any of your content is trapped inside an image.
The centrepiece of the output is not a checklist. It is a panel showing the raw extracted text, verbatim, in the order a parser reads it. Nobody argues with a score; everybody believes their own resume rendered as garbled text.
Multi-column layouts are the real failure mode
The single most common reason a well-written resume fails machine screening is a two-column template. A human reads the sidebar as a sidebar; a parser reads whatever the PDF's internal drawing order gives it, which frequently interleaves your skills list into the middle of a job description.
We detect this by extracting twice - once in the document's default order, once sorted by position on the page - and comparing. When the two disagree materially, the layout is scrambling, and we show you both versions so you can see it for yourself rather than take our word for it.
If your resume is an image, that is the finding
Some resumes are exported as a single flattened image, usually from a design tool. Those files are invisible to every applicant tracking system in existence - not scored badly, not read at all. When we find no extractable text, we say exactly that and treat it as the most important result this tool can produce, rather than showing you a generic upload error.
There is no OCR here, and that is intentional. Reading your image with OCR would tell you what the picture says, which is not the question. The question is what the parser gets, and the parser gets nothing.
What it will not do
It will not score your resume out of 100, judge your writing, or suggest rewrites. No AI model is involved on any code path, and no outbound network request is made while your file is being processed. It is a narrow, boring, permanently free tool - and that narrowness is precisely why its output is trustworthy.