An ATS résumé checker compares the words in your résumé with the words in a job posting and reports the overlap. It can show you which terms you are missing. It cannot tell you whether a particular company's system would reject you, because in most cases it would not.
What a checker measures
Most checkers do some version of the same thing: pull out the skills and keywords in a job description, look for them in your résumé, and turn the match into a score. Some also flag layout choices that can trip up résumé parsers, such as text inside images or unusual section headings.
What it cannot tell you
A score is not a prediction of an outcome. In a late-2025 interview study of 25 US recruiters by Enhancv, 92% said their ATS does not auto-reject résumés based on content, formatting or design, and only 2 of the 25 had set up any content-based auto-rejection at all.
So a low score does not mean a system threw your résumé away. It means a recruiter searching for those terms may not find you, and a reader skimming for them may not see them.
How to use a score well
Treat each missing keyword as a question, not a to-do. Do you have this skill or experience? If yes, say so in the posting's words, in the place it belongs. If no, leave it out and decide whether you still want to apply.
Do not chase 100%. Adding terms you cannot defend raises the number and lowers your credibility the moment someone asks about them.
Safe formatting habits
As a precaution rather than a rule, keep the layout simple: standard section headings, real text instead of images, and an export format the employer asks for. These cost you nothing and remove one possible source of parsing trouble.
A free way to check
Weydr's free résumé keyword checker compares a job description with your résumé and lists the keywords you already match and the ones that are missing. It runs in your browser with no signup, and nothing you paste is sent to our servers or stored.