How ATS Parsers Actually Work \u2014 What Your Resume Goes Through Before a Recruiter Sees It
ATS parsers break your resume into sections, extract keywords from the job description, and score how well you match — all in under two seconds. They do not reject resumes or block you from recruiters. Instead, they present a ranked, scannable view that determines whether a recruiter clicks on your profile or skips to the next candidate. Here is exactly how they work and how to optimize for them.
Most candidates treat ATS as a black box. You upload a resume, get a score, and have no idea what happened in between. But the parsing process is surprisingly predictable once you understand the three stages.
Stage 1: Parsing \u2014 How the System Reads Your Resume
The parser starts by converting your resume file (PDF, DOCX, or plain text) into raw text. This step sounds simple but is where most failures happen.
What parsers handle well:
- Standard DOCX files \u2014 Native Microsoft Word format parses cleanly because the text layer is intact
- Digitally created PDFs \u2014 Saved from Word or Google Docs, these retain selectable text
- Plain text \u2014 Minimal formatting, zero parsing errors
What parsers fail on:
- Scanned PDFs \u2014 The parser sees an image, not text. Optical character recognition (OCR) may recover some content but regularly misses critical details
- Tables and columns \u2014 Multi-column layouts confuse parsers. They read left-to-right, top-to-bottom, turning column B content into the middle of column A
- Headers and footers \u2014 Many ATS platforms (especially Workday) ignore content in headers, so your contact info, name, and critical keywords placed there simply vanish
- Text boxes and graphics \u2014 These are non-standard elements that most parsers cannot interpret
Key insight: The #1 cause of low ATS scores is not missing keywords \u2014 it is formatting that prevents the parser from finding the keywords you already have.
Stage 2: Section Identification \u2014 How the Parser Knows What is What
After extracting raw text, the parser needs to identify which parts of your resume are Experience, Education, Skills, and so on. It does this by looking for standard section headers.
| Section Header | Parser Recognition Rate | Best Practice |
|---|---|---|
| Experience / Work History | 98% | Use exactly "Experience" or "Work Experience" |
| Education | 97% | Use "Education" \u2014 avoid "Academic Background" |
| Skills | 95% | Place above Experience for maximum visibility |
| Summary / Objective | 85% | Use "Professional Summary" \u2014 avoid creative titles |
| Certifications | 88% | Use "Certifications" or "Licenses" |
Using creative section headers like "Where I Have Worked" or "My Toolbox" confuses parsers. The system either misclassifies the content or drops it entirely. Always use standard headers that match what the ATS expects.
Stage 3: Keyword Extraction and Scoring
This is the most important stage. The ATS compares the keywords in your resume against the keywords in the job description and calculates a match score.
Different ATS platforms weight keywords differently:
- Workday \u2014 Contextual matching. It considers where keywords appear (Skills section = higher weight than a passing mention in Experience)
- Taleo \u2014 Frequency-based. It counts how many times a keyword appears. More mentions = higher score, even if placement is awkward
- iCIMS \u2014 Skills database matching. It compares your listed skills against a built-in database and scores based on coverage
- Greenhouse \u2014 Structured scoring. It uses a custom rubric set by the employer, pulling from specific fields in your application
Practical takeaway: If you are applying to a company you know uses Workday, prioritize putting keywords in your Skills section. For Taleo, repeat critical keywords naturally throughout your resume. Most large enterprises use Workday or Taleo.
The 3 Most Common Parsing Errors \u2014 And How to Fix Them
Our analysis of thousands of ATS scans at RezzoBot reveals three parsing errors that consistently destroy match scores:
Error #1: Contact info in headers or footers
Workday and Taleo both ignore header content. Your phone number, email, and LinkedIn profile placed in the header are invisible. Fix: Place all contact information in the main body of the document, above your summary section.
Error #2: Multi-column layouts
A two-column resume with skills on the left and experience on the right gets parsed as a jumbled mess. The parser reads across columns, mixing your tools list into your job descriptions. Fix: Use a single-column layout. It is boring but parsable.
Error #3: Skills buried at the bottom
Many candidates list skills at the end, after education. Parsers reading from top to bottom may stop before reaching the skills section if the resume is long. Fix: Place your Skills section immediately below your summary and above your experience.
How Different ATS Systems Compare
| Feature | Workday | Taleo | iCIMS | Greenhouse |
|---|---|---|---|---|
| PDF parsing | Good | Moderate | Good | Excellent |
| DOCX preferred? | Yes | Yes | Yes | Yes |
| Section header strictness | Medium | High | Medium | Low |
| Keyword matching style | Contextual | Frequency | Skills DB | Custom |
| Header/Footer support | No | No | Partial | Yes |
How RezzoBot Checks Your Resume Against ATS
RezzoBot simulates how real ATS parsers work. When you upload your resume and paste a job description, we:
- Parse your resume the way Workday and Taleo do — extracting section headers, detecting formatting issues, and flagging elements that parsers cannot read
- Extract keywords from the job description and compare them against your resume, word by word
- Score your match based on keyword density, placement, and section structure — exactly how enterprise ATS platforms score candidates
- Show you exactly what to fix — missing keywords, format issues, and section problems — in plain language
Unlike generic checkers that give you a number and nothing else, RezzoBot shows you which specific keywords are missing and where your formatting is costing you points.
Frequently Asked Questions
How does an ATS parser work?
An ATS parser reads your resume by breaking it into sections (Experience, Education, Skills), extracting keywords that match the job description, and scoring how well your resume aligns with what the employer is looking for. It does not reject resumes — it ranks them for recruiters.
What can ATS parsers not read?
ATS parsers cannot read text embedded in images, headers or footers, tables, columns, text boxes, graphics, or unusual fonts. They also struggle with PDFs that were scanned from paper. Complex formatting is the number one cause of parsing errors.
Do different ATS systems parse resumes differently?
Yes. Workday, Taleo, iCIMS, and Greenhouse all parse resumes slightly differently. Workday is best at contextual keyword matching. Taleo is stricter about section headers. iCIMS relies heavily on skills databases. Optimizing for one usually works for all if you follow standard formatting.
Should I submit my resume as PDF or DOCX?
DOCX is safer for most ATS platforms. PDF works if it was created digitally (not scanned), but some older systems like Taleo parse DOCX more reliably. Only use PDF when a job posting specifically requests it.
Can I check if my resume passes ATS for free?
Yes. RezzoBot offers a free ATS resume check that scores your resume, shows matched and missing keywords, and flags formatting issues — no credit card required.
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