How ATS Systems Actually Work Behind the Scenes

TL;DR: Applicant tracking systems are not the resume black holes most job seekers imagine. The four dominant platforms — Workday, Greenhouse, Lever, and iCIMS — each parse, store, and rank your resume differently, and understanding those differences gives you a real edge. Most ATS myths are outdated or flat-out wrong, and the actual mechanics are more straightforward than you think.

Key Takeaways

• Over 98% of Fortune 500 companies and 75% of all mid-to-large employers use an ATS to manage hiring, making it nearly impossible to avoid one during your job search [1]
• Workday, the most widely used enterprise ATS, relies on a structured-field parser that maps your resume data into predefined categories rather than doing free-text keyword matching [2]
• Greenhouse and Lever use more flexible parsing engines that handle varied resume formats better, but they still struggle with tables, text boxes, and multi-column layouts [3]
• No major ATS automatically rejects candidates — they score and rank applicants, and a human recruiter always makes the screening decision [4]
• The single most impactful thing you can do for ATS compatibility is use a clean, single-column format with standard section headings like "Experience," "Education," and "Skills" [5]

What Is an Applicant Tracking System and Why Should You Care?

An applicant tracking system is the software that sits between you clicking "Apply" and a recruiter seeing your resume. Every application you submit to a mid-size or large company passes through one of these platforms before a human being ever looks at it. According to Jobscan's 2025 ATS market analysis, roughly 98.8% of Fortune 500 companies use an ATS, and adoption among companies with more than 50 employees has crossed the 75% threshold [1].

The ATS does three fundamental things with your application. First, it receives and stores your submitted documents — your resume file, cover letter, and any form fields you fill out. Second, it parses that information by extracting text and mapping it into structured data fields like job titles, company names, dates of employment, education details, and skills. Third, it provides tools for recruiters to search, filter, and rank the applicant pool based on criteria they define.

What an ATS does not do — despite widespread belief — is automatically throw your resume in the trash. The "black hole" reputation comes from the fact that many recruiters receive hundreds of applications per role and simply cannot review every single one in detail. The ATS helps them prioritize, but the decision to pass or reject is made by a person. Understanding how your resume gets parsed and presented to that person is where the real advantage lies.

If you are working on getting your resume past these systems, our ATS optimization guide covers the foundational formatting strategies that apply across all platforms.

How Does Resume Parsing Actually Work?

Resume parsing is the process of converting an unstructured document — your resume file — into structured data that the ATS can store in its database. Think of it like translating a printed letter into a spreadsheet. The parser needs to figure out which block of text is your name, which is your current job title, where your work history starts and ends, and what counts as a skill versus a certification.

Modern ATS parsers use a combination of pattern recognition, natural language processing, and rules-based logic to accomplish this. They look for formatting cues like section headers, date patterns, bullet points, and spatial positioning on the page. When they encounter "Senior Product Manager | Acme Corp | Jan 2022 – Present," the parser identifies a job title, a company name, and a date range based on learned patterns.

Here is where things get interesting: different ATS platforms use different parsing engines, and they do not all handle the same resume the same way. Some parsers are proprietary and built in-house, while others license third-party parsing technology from companies like Sovren (now Textkernel), Daxtra, or Affinda [3]. The parser your resume encounters depends entirely on which ATS the employer uses — and you typically have no way of knowing that before you apply.

The most common parsing failures happen when the parser encounters formatting it was not trained to handle. Tables, text boxes, headers and footers, columns, graphics, and unusual fonts can all cause the parser to misread or skip sections of your resume entirely. The result is not rejection — it is mangled data. Your job title might end up in the education field, your dates might disappear, or your skills section might merge into a single unreadable string. When a recruiter pulls up your parsed profile and sees garbled information, they are unlikely to dig into the original document to figure out what you actually wrote.

How Does Workday's ATS Handle Your Resume?

Workday dominates the enterprise ATS market. As of early 2026, it powers talent acquisition for more than 60% of Fortune 500 companies, including Amazon, Walmart, Target, Bank of America, and dozens of other household names [2]. If you are applying to a large corporation, there is a better-than-even chance your resume is going through Workday.

Workday's approach to resume processing is notably structured. When you apply through a Workday-powered careers page, you are typically asked to upload your resume and then manually fill out fields for your work history, education, and contact information. Workday parses your uploaded resume to pre-fill those fields, but it relies heavily on the structured data you enter in the form rather than doing deep free-text analysis of your document.

This has a practical implication most job seekers overlook: in Workday, the information you type into the application form often matters more than the resume file you upload. The resume file is stored and available for the recruiter to view, but the searchable, filterable database that recruiters use to find candidates is built from the structured fields. If you rush through the form, leave fields blank, or let the parser auto-fill without checking for errors, you are undermining your own visibility in the system.

Workday's search functionality allows recruiters to filter candidates by job title, company, years of experience, location, skills, and education. Recruiters can also set up "disposition" workflows that move candidates through stages like "Review," "Phone Screen," "Interview," and "Offer." Your resume's compatibility with Workday is less about keywords in the document and more about the completeness and accuracy of the structured data associated with your profile.

For more on matching your resume language to job descriptions within systems like Workday, check out our ATS keyword strategy guide.

How Do Greenhouse and Lever Differ From Workday?

While Workday targets the enterprise segment, Greenhouse and Lever have carved out dominant positions among mid-market companies, high-growth startups, and the tech industry. Greenhouse counts more than 7,500 companies among its customers, including HubSpot, Cisco Meraki, and Booking.com [6]. Lever, now part of Employ Inc. after its 2022 merger with Jobvite, serves companies like Netflix, KPMG, and Shopify [7].

Both Greenhouse and Lever take a more document-centric approach to resume handling compared to Workday. When you submit an application, the ATS parses your resume file and uses that parsed data as the primary source of candidate information. There is less reliance on manually filled forms, which means the quality of parsing matters more.

Greenhouse uses a combination of third-party and proprietary parsing technology. Its parser does a solid job with standard resume formats — single-column layouts, clear section headings, chronological work history. It extracts contact information, work experience, education, and skills, then presents a structured candidate profile to the recruiter alongside the original resume document. Greenhouse also integrates with more than 500 third-party tools, which means your data might flow through additional parsing layers if the company uses add-ons for skills assessment or background checks [6].

Lever distinguishes itself with what it calls "nurture" functionality — the ability to treat candidates as long-term relationships rather than one-time applicants. From a parsing perspective, Lever handles resumes similarly to Greenhouse, but it places more emphasis on building a searchable talent database over time. If you applied to a company using Lever two years ago, your profile likely still exists in their system, and a recruiter can find it when a relevant new role opens up.

Here is a practical comparison of how these platforms differ in their handling of common resume elements:

Feature	Workday	Greenhouse	Lever	iCIMS
Primary data source	Form fields	Parsed resume	Parsed resume	Parsed resume + form
PDF parsing quality	Good	Very good	Very good	Good
Handles multi-column layouts	Poor	Moderate	Moderate	Poor
Skills extraction	Basic	Advanced	Advanced	Advanced
Candidate search method	Structured filters	Full-text + filters	Full-text + filters	AI-ranked + filters
Typical employer size	Enterprise, 10,000+	Mid-market, 500-10,000	Mid-market, 200-5,000	Enterprise + mid-market
Market share estimate	~60% of Fortune 500	~7,500 customers	~5,000 customers	~4,000 enterprise clients

What About iCIMS — the Enterprise Challenger?

iCIMS rounds out the "big four" of applicant tracking systems, serving roughly 4,000 enterprise and mid-market employers including Target (alongside Workday), UPS, and Johnson & Johnson [8]. Where iCIMS sets itself apart is in its use of AI-powered candidate matching that goes beyond simple keyword lookups.

iCIMS's parsing engine extracts standard resume fields — contact information, work history, education, skills — but then layers on a matching algorithm that compares parsed candidate data against the requirements listed in the job posting. The system assigns a fit score that recruiters can use to prioritize their review queue. This is closer to what most people imagine an ATS does, but it is still not automatic rejection. The fit score is a sorting tool, not a gatekeeper [8].

The iCIMS platform also includes a feature called "candidate relationship management" that functions similarly to Lever's nurture tools. Employers can build talent pools, send targeted communications to past applicants, and resurface strong candidates when new roles match their profiles. For job seekers, this means that a well-crafted application to an iCIMS-powered company can continue working for you long after the specific role you applied for has been filled.

One notable technical detail about iCIMS: its parser tends to handle DOCX files slightly better than PDFs in some configurations. While PDF support has improved significantly across all major ATS platforms in recent years, iCIMS documentation still recommends DOCX as the preferred format for optimal parsing accuracy [8]. That said, a cleanly formatted PDF will work fine in the vast majority of cases.

What ATS Myths Should You Stop Believing?

The internet is full of ATS advice that was either never true or stopped being true years ago. Let us clear up the most persistent myths so you can focus your energy on strategies that actually matter.

Myth 1: ATS systems reject 75% of resumes before a human sees them. This statistic has been circulating since at least 2012, and its origin is murky at best. No major ATS vendor has ever confirmed an automatic rejection rate. What is true is that many job postings receive hundreds of applicants, and recruiters may only review a portion of them. But the ATS is not making that cut — the recruiter is, often by sorting on criteria like years of experience or specific skills [4].

Myth 2: You need to stuff your resume with exact keyword matches. Modern ATS search engines understand synonyms and related terms. If a recruiter searches for "project management," most platforms will also return results for "PM," "program management," and "project lead." Keyword stuffing — especially the old trick of hiding white text on a white background — is more likely to hurt you than help you. Recruiters who discover keyword stuffing consider it a red flag, and some ATS platforms have detection for hidden text [5].

Myth 3: You must use a .docx file, never a PDF. This was partially true a decade ago when PDF parsing was genuinely unreliable. As of 2026, all four major ATS platforms handle PDFs competently. The key variable is not the file format — it is the formatting within the document. A messy, graphics-heavy DOCX will parse worse than a clean, well-structured PDF every time [3].

Myth 4: Creative or designed resumes are automatically filtered out. The ATS does not have aesthetic preferences. It does not care if your resume looks beautiful or plain. What it cares about is whether it can extract structured text from the document. A visually stunning resume that uses standard text (not embedded in images) and a logical reading order will parse just fine. A bland resume that uses tables and text boxes will parse terribly. Design is fine; structural complexity is the problem.

Myth 5: There is a secret ATS score that determines if you get an interview. While some ATS platforms do generate match scores (iCIMS being the most prominent example), these scores are visible only to recruiters, vary widely in how they are calculated, and are just one of many factors recruiters consider. There is no universal "ATS score" and no magic number you need to hit.

For a deeper dive into formatting your resume to avoid common parsing pitfalls, our ATS-friendly resume formatting guide walks through specific layout recommendations for each major platform.

How Can You Optimize Your Resume for Any ATS?

Given the differences between platforms, the smartest strategy is to follow formatting principles that work well across all of them. You do not need to know which ATS a company uses — you need a resume that any parser can handle cleanly.

Start with a single-column layout. Every major ATS parser reads top-to-bottom, left-to-right. Multi-column designs, sidebar layouts, and text arranged in tables force the parser to guess the reading order, and those guesses are wrong often enough to be a real risk. A single column eliminates that uncertainty entirely.

Use standard section headings. "Experience," "Work Experience," or "Professional Experience" will be recognized by every ATS parser on the market. The same goes for "Education," "Skills," "Certifications," and "Summary." Creative headings like "Where I've Made an Impact" or "My Toolkit" may look good to humans, but parsers are trained on conventional section names and may misclassify content under non-standard headers [5].

Keep your formatting simple. Bold and italic text are fine. Standard bullet points are fine. Basic horizontal lines between sections are usually fine. What is not fine: text boxes, tables used for layout, images with text embedded in them, headers and footers containing critical information (many parsers ignore header and footer regions entirely), and custom fonts that may not render on the parsing server.

Include your contact information in the body of the document, not in the header. This is one of the most common mistakes. Job seekers put their name, phone number, and email in the document header because it looks clean, but ATS parsers frequently skip header content. Put your contact details as plain text at the top of the page body.

For each role in your work history, include the job title, company name, location, and dates in a consistent format. Parsers use these elements to construct your career timeline. If your formatting varies between roles — sometimes the company is first, sometimes the title, sometimes the dates are on a separate line — the parser has to work harder to make sense of it, increasing the chance of errors.

If you want to see how your resume currently performs through an actual parsing test, our ATS resume checker tools comparison reviews the best options for testing your resume against real parsing engines.

Why This Matters

As of May 2026, the ATS market continues to consolidate around a handful of dominant platforms, and the trend toward AI-powered candidate matching is accelerating. Workday, Greenhouse, Lever, and iCIMS collectively process the majority of job applications submitted in the United States and an increasing share of global applications. LinkedIn's 2025 Global Talent Trends report found that 82% of talent acquisition leaders plan to increase their reliance on ATS automation in the next two years [9].

Understanding how these systems actually work — rather than relying on outdated myths — is not optional anymore. It is a core job search skill. The candidates who get interviews are not gaming the system with hidden keywords or formatting tricks. They are presenting their qualifications clearly enough for both software and humans to understand, and they are paying attention to the structured data fields that actually drive recruiter search results.

The good news is that ATS-friendly formatting is not at odds with good resume design. A clean, readable, well-organized resume that works for a parser also works for the human being who ultimately decides whether to schedule that phone screen. Focus on clarity, consistency, and completeness, and you will be well-positioned regardless of which platform is on the other end of that "Apply" button.

FAQ

Q: Do ATS systems automatically reject resumes? A: No. The major ATS platforms — Workday, Greenhouse, Lever, and iCIMS — parse and rank applicants but do not auto-reject anyone. A human recruiter always makes the decision about who advances in the hiring process. The perception of automatic rejection comes from the high volume of applications most roles receive combined with limited recruiter bandwidth.

Q: Which ATS is used most by Fortune 500 companies? A: Workday is the dominant ATS among Fortune 500 employers, powering talent acquisition for over 60% of the largest companies in the United States as of 2025. iCIMS holds the second-largest enterprise market share, followed by platforms like SAP SuccessFactors and Oracle Taleo in specific verticals.

Q: Can an ATS read PDF resumes? A: Yes. All four major ATS platforms can parse PDF resumes reliably in 2026. The key factor is not the file format but the formatting inside the document. A clean, single-column PDF with standard section headings will parse accurately on any modern platform. Complex layouts with tables, text boxes, or embedded graphics can cause problems in any file format.

Q: Do ATS systems penalize creative resume designs? A: ATS parsers do not evaluate visual design — they extract text. A creative resume with strong visual elements will parse fine as long as the text is actual text (not embedded in images) and the layout follows a logical single-column reading order. The problem is not creativity itself but structural complexity like multi-column layouts, tables used for positioning, and text hidden in graphical elements.

Q: How often do companies change their ATS platform? A: Enterprise ATS contracts typically last three to five years, and switching costs are high due to data migration, workflow reconfiguration, and recruiter retraining. Mid-market companies may switch more frequently, especially during rapid growth phases, but the general trend is toward long-term platform commitments.

Sources

[1] Jobscan, "ATS Market Share and Usage Report 2025," https://www.jobscan.co/blog/ats-market-share/

[2] Workday, "Workday Recruiting Overview," https://www.workday.com/en-us/products/talent-management/recruiting.html

[3] Textkernel (formerly Sovren), "Resume Parsing Technology Documentation," https://www.textkernel.com/solution/resume-parsing/

[4] SHRM, "How Applicant Tracking Systems Work," https://www.shrm.org/topics-tools/news/talent-acquisition/how-applicant-tracking-systems-work

[5] TopResume, "ATS Resume Formatting Guide 2025," https://www.topresume.com/career-advice/what-is-an-ats-resume

[6] Greenhouse, "About Greenhouse — Company Overview," https://www.greenhouse.com/company

[7] Employ Inc., "Lever by Employ — Enterprise Recruiting Platform," https://www.lever.co/

[8] iCIMS, "Talent Cloud Platform Overview," https://www.icims.com/products/talent-cloud-platform/

[9] LinkedIn, "Global Talent Trends 2025," https://business.linkedin.com/talent-solutions/global-talent-trends