Inside the ATS Algorithm (Explained Simply)

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Inside the ATS Algorithm (Explained Simply)

If you've ever applied for a job online and heard nothing back, you might be wondering: Was my resume even seen by a human? In many cases, it wasn’t. Welcome to the world of Applicant Tracking Systems (ATS)—the gatekeepers of modern hiring.

In this article, we’ll break down how ATS works, how it reads and scores your resume, and what steps you can take to make sure you’re not filtered out before your resume is ever seen by a recruiter. We’ll also explain the core mechanisms behind resume parsing, keyword ranking, formatting issues, and why good candidates get rejected.

By the end, you’ll know how to beat the ATS filters and get your resume in front of real decision-makers.

What is an Applicant Tracking System?

An Applicant Tracking System (ATS) is a type of HR software that automates the initial stages of recruiting. Companies use ATS platforms to collect, scan, and rank resumes submitted for open positions.

Popular ATS tools include Greenhouse, Workday, Lever, and Taleo. Over 75% of companies now use some form of ATS—and the number is even higher among large corporations.

Why ATS Exists (and Why It’s a Problem for Job Seekers)

Recruiters are often flooded with hundreds of applications for each job. The ATS helps filter that flood by scanning resumes for relevant experience, skills, and keywords. While this automation saves time for hiring teams, it creates a major barrier for job seekers:

If your resume isn't properly formatted or doesn't contain the right keywords, it might be rejected—without anyone ever reading it.

How ATS Reads and Parses Your Resume

The ATS doesn’t “read” like a human. It parses your resume by breaking it down into structured data. Think of it as converting your PDF into a spreadsheet with rows for:

  • Name
  • Education
  • Work Experience
  • Skills
  • Keywords

Then, it ranks you based on how closely this data matches the job description. This is why resume optimization is so important.

Step-by-Step: What Happens After You Hit "Submit"

Let’s walk through what happens when you apply for a job through an ATS:

  1. Resume Parsing Begins: Your file is scanned and segmented.
  2. Text Extraction: The system strips away visuals and formatting to extract raw text.
  3. Keyword Matching: The ATS compares your text to the job description.
  4. Scoring and Ranking: You get a match score—higher means you’re more likely to be seen.
  5. Human Review (Optional): Only the top-ranking candidates are usually reviewed.

Now imagine you used a funky font, put your job titles inside text boxes, or wrote your experience in vague terms. The system might fail to parse or match your content—and you’re out.

What Causes ATS Rejection?

  • Unrecognized formatting: Tables, columns, and graphics confuse the parser.
  • Missing keywords: If you don’t include the right resume keywords, the system won’t consider you relevant.
  • Wrong file type: Some ATS reject resumes that aren’t PDF or DOCX.
  • Overdesign: Design-heavy templates often result in parsing errors.

Want a concrete example? If the job asks for "JavaScript" but your resume only says "Frontend Technologies," that’s a miss. The ATS is looking for exact matches.

Learn more in our guide: Why You’re Getting Rejected Without an Interview.

ATS Resume Tips That Work in 2025

  1. Use Standard Headers: Stick with "Experience," "Education," and "Skills."
  2. Keep Formatting Simple: No columns, text boxes, or background images.
  3. Use Bullet Points for Clarity: But only plain text bullets like dashes or asterisks.
  4. Match Keywords from the Job Posting: Tools like ResumeAdapter can help you identify missing ones.
  5. Include a Skills Section: This helps the ATS recognize technical and soft skills.

Let’s Talk Keywords

In 2025, keyword optimization is not optional—it’s essential. The ATS ranks resumes based on:

  • Hard skills: e.g. Python, React, SQL
  • Soft skills: e.g. communication, problem-solving
  • Certifications: e.g. AWS Certified Developer
  • Job titles: Match past roles to what the employer is looking for

Check out our curated 2025 resume keyword list for junior developers.

Debunking Myths About ATS

  • “Only bots decide who gets hired” — False. The ATS helps screen, but humans make final decisions.
  • “Graphics make your resume stand out” — Not to an ATS. Avoid.
  • “You only need one resume” — Wrong. Customize for each job posting.

Real Example: ATS Resume Analysis with ResumeAdapter

Let’s say you upload your resume to ResumeAdapter. Here’s what happens:

  • We extract the raw text from your resume.
  • Compare it to the job description.
  • Highlight missing or weak keywords.
  • Estimate your match score.
  • Offer instant suggestions to improve your chances.

It’s fast, free, and incredibly helpful if you’ve been ghosted by employers recently.

Why This Matters More Than Ever

With AI transforming hiring in 2025, recruiters are relying even more on automation. That means:

  • Your first impression is algorithmic
  • Well-qualified people still get filtered out
  • Small changes make big differences

Final Thoughts

Understanding how applicant tracking systems work is a game-changer. It’s not about “gaming the system”—it’s about speaking the same language as the software that stands between you and your next interview.

If you're ready to stop guessing and start improving, head over to ResumeAdapter and scan your resume now. You’ll get a real-time score, keyword insights, and a path to get seen.

✅ Want to go deeper? Read our post on How to Instantly Analyze Your Resume for ATS with ResumeAdapter.