How ATS Systems Work — And Why Your Resume Gets Rejected

What is an Applicant Tracking System (ATS)?

An Applicant Tracking System (ATS) is software used by employers to collect, sort, scan, and rank job applications. According to research by Jobscan, over 98% of Fortune 500 companies use ATS software, and even small and medium businesses are increasingly adopting these tools to manage high volumes of applications. A single corporate job posting can receive hundreds to thousands of applications; without automated filtering, the process would be unmanageable.

When you submit a resume online, it almost never goes directly to a human recruiter. Instead, it enters an ATS queue where it is parsed, analysed, and scored against the job description. If your resume does not score high enough, it is filtered out — and no human ever sees it. This is not a coincidence or an anomaly: it is the intended design of the system.

Understanding how ATS software works is not optional for modern job seekers — it is essential. Candidates who understand the system and optimise for it consistently get more interview invitations than equally qualified candidates who do not.

How Does an ATS Actually Parse Your Resume?

ATS software reads your resume much like a basic text reader — it extracts text, identifies sections, and pulls out key information. Here is what happens step by step when you click "submit":

1. Text extraction: The ATS converts your resume file (PDF, DOCX, or TXT) into plain text. Fancy formatting, tables, text boxes, and graphics are often stripped away or misread entirely. A two-column resume that looks beautiful in Adobe Reader may become a garbled mess of text when parsed by an ATS.
2. Section identification: The software looks for standard section headers like "Experience," "Education," "Skills," and "Summary." Non-standard headers like "Where I Have Worked" or "My Journey" may not be recognised, causing your experience to be misfiled or ignored entirely.
3. Data extraction: The ATS attempts to extract structured data — your job titles, company names, dates of employment, educational qualifications, and skills. Errors in this step mean your actual experience does not show up correctly in the employer's candidate profile.
4. Keyword matching: The ATS compares the text in your resume against keywords in the job description. The more keywords match — particularly in the right context — the higher your score.
5. Ranking: Resumes are ranked by match score and only the top candidates — typically those with a score above 75–80% — are passed to a recruiter for review. Everyone below that threshold is effectively invisible.

Why Do Most Resumes Get Rejected by ATS?

There are several common reasons a resume fails ATS screening even when the candidate is fully qualified. Many of these failures have nothing to do with the candidate's actual experience — they are purely technical or formatting issues that are entirely preventable.

• Missing keywords: The resume does not include exact phrases from the job description. ATS systems are often literal — they look for "project management" not "managing projects." This is the single most common reason for rejection and the most fixable.
• Wrong file format: Some ATS systems cannot parse PDFs created from design tools like Canva, Figma, or InDesign. These tools produce PDFs that are essentially images, not searchable text. A plain PDF or DOCX file created in Word or Google Docs is safest.
• Complex formatting: Multi-column layouts, tables, headers and footers, and text boxes confuse the parser. The text may appear in the wrong order or not at all. The ATS cannot "see" the layout — it only reads the text stream.
• Images and graphics: Any text embedded in an image — including your name in a logo, contact info in a header image, or infographic-style skills bars — is completely invisible to the ATS. Never put important information inside images.
• Non-standard section headers: Using creative names for sections can prevent the ATS from correctly categorising your experience and education. "Career Highlights" instead of "Experience," or "Academic Background" instead of "Education," may cause sections to be missed entirely.
• Spelling and abbreviations: The ATS may not connect "JS" with "JavaScript" or "PM" with "Project Manager" unless both forms appear in your resume. It will also not correct typos — "managment" will not match "management."
• Missing dates: Many ATS systems calculate your years of experience by parsing your employment dates. If dates are missing or formatted unusually (e.g., "Summer 2019" instead of "June 2019"), the calculation may fail or exclude that role entirely.

What Is an ATS Score and How Is It Calculated?

Different ATS platforms calculate scores differently, but most use a combination of weighted factors. Understanding these gives you a clear picture of where to focus your optimisation effort:

• Keyword frequency and relevance: How many job description keywords appear in your resume, and how prominently (in your summary and title vs. buried in a bullet point in your oldest role). Keywords at the top of the document carry more weight.
• Skills match: Hard skills mentioned in the job description that appear in your skills section or experience. Matching all required skills is more important than matching some required and some optional skills.
• Job title similarity: Whether your past job titles match or are close to the target role. This is why it can be worth including the target job title in your resume summary, even if your current title is slightly different.
• Years of experience: Some ATS systems parse dates and calculate total experience in specific roles. A requirement for "5+ years of experience in X" may be checked automatically against your employment history.
• Education requirements: Degree level and field of study matched against the job requirements. If a role requires a bachelor's degree and your resume does not clearly state one, you may be auto-filtered.
• Certifications: Professional certifications (PMP, AWS Certified, CPA, etc.) are high-value keywords that many ATS systems scan for specifically, particularly in regulated industries.

A score of 80% or above is generally considered a strong match. Scores below 60% are almost always auto-rejected before human review.

The Most Common ATS Platforms and How They Differ

Not all ATS systems are the same. The major platforms used by employers include:

• Workday: Used by large enterprises. Very strict about formatting and section structure. Workday also has its own application forms that often ask you to re-enter resume data manually after uploading — take care to ensure consistency.
• Taleo (Oracle): One of the oldest and most widely used systems, common in large corporations. Heavily keyword-dependent and known for being particularly unforgiving of formatting issues.
• Greenhouse: Common at tech companies and startups. More flexible parsing than Taleo or Workday. Better at reading varied formats, but keyword matching still matters.
• Lever: Popular with modern tech companies. Better at reading varied formats and has stronger recruiter-facing search tools, meaning keyword optimisation is still critical but formatting flexibility is slightly higher.
• iCIMS: Used across industries, particularly in healthcare, retail, and manufacturing. Scores heavily based on keyword match against job requirements.
• SmartRecruiters: Growing adoption in mid-market companies. Has more AI-assisted matching than older platforms.

While each platform has its quirks, the core optimisation strategies work across all of them: clean formatting, relevant keywords in standard sections, and complete, accurate information.

How to Know if a Company Uses ATS

As a general rule, if you are applying through an online portal or clicking a link to an application page, you are going through an ATS. The vast majority of employers above a certain size use these systems for any role that receives significant application volume.

Signs that an application is ATS-managed:

• You are redirected to a platform like Workday, Greenhouse, Lever, or Taleo after clicking "Apply"
• The URL changes to one of these platform domains during your application
• You are asked to create an account on the company's job portal
• The application asks you to re-enter information from your resume in structured fields

Direct applications via email to a person you know, or through a referral where your resume goes directly to the hiring manager, may bypass the ATS entirely. This is one reason why networking is so valuable in job searching — your resume reaches a human first.

How to Optimise Your Resume for ATS

Here are the most impactful changes you can make to ensure your resume passes ATS screening:

1. Mirror the job description language: Read the job posting carefully and use the same words and phrases they use. If they say "cross-functional collaboration," use that exact phrase — not "worked across teams." If they list specific tools, use those names exactly as written.
2. Use standard section headers: Stick to Work Experience, Education, Skills, Summary, and Certifications. These are universally recognised by all major ATS platforms.
3. Use a single-column layout: Multi-column resumes look great to humans but break ATS parsing. Use a single-column format with clear sections. Your resume will still look professional — it will just be formatted in a way the software can read.
4. Include both acronyms and full forms: Write "Search Engine Optimization (SEO)" or "Project Management Professional (PMP)" to ensure both versions are matched, since job descriptions and ATS queries vary in which form they use.
5. Avoid headers, footers, and text boxes: Put your contact information in the main body of the document, not in a Word header or footer. Text in these areas is often completely invisible to ATS parsers.
6. Save as DOCX or simple PDF: Create your resume in Word or Google Docs and save as DOCX or a standard PDF — avoid design tools like Canva or Illustrator for ATS submissions.
7. Quantify achievements: Numbers and metrics (increased sales by 30%, managed a team of 15, reduced costs by £50K) add specificity that reinforces keyword matches and makes your accomplishments credible.
8. Tailor for each application: There is no universal "ATS-proof" resume. Each application needs a customised version that reflects that specific job's requirements. Your summary, skills section, and top bullet points should change for each role.
9. Spell out dates consistently: Use a consistent date format throughout — "January 2022 – March 2024" or "01/2022 – 03/2024." Do not mix formats or omit years.
10. Do not use images, logos, or icons: Even decorative icons next to section headers can confuse the parser. Keep the resume as clean text throughout.

Testing Your Resume Before Applying

Before submitting a resume for any important role, it is worth testing how the ATS will read it. There are a few ways to do this:

• Paste into plain text: Copy and paste your resume into a plain text editor (Notepad on Windows, TextEdit in plain text mode on Mac). If the result is garbled, out of order, or missing sections, an ATS will likely have the same problem.
• Use a keyword matching tool: Paste your resume and the job description into a tool that calculates keyword match — this immediately shows you which required terms are missing and where your score stands before you apply.
• Check file size and format: Your resume file should typically be under 2MB. Files above this can cause upload failures on some platforms. If your PDF is very large, it may contain embedded graphics that will cause parsing issues.

How AiResumeFit Helps You Pass ATS

Manually optimising your resume for every job application takes time and expertise. AiResumeFit automates this entire process:

• Analyses the job description and identifies every important keyword the ATS will be looking for
• Rewrites your resume to naturally incorporate those keywords in the right sections and with appropriate context
• Shows you a before-and-after ATS score so you can see exactly how much the optimisation improved your match
• Highlights exactly which keywords were missing and have been added to your resume
• Produces a clean, single-column resume format in professional LaTeX quality that every ATS can read correctly
• Downloads as both PDF and DOCX so you can choose the right format for each submission

Most users see their ATS score jump from around 45–55% to 90–97% after optimisation — which means moving from the rejection pile to the top of the recruiter's shortlist. The optimisation takes under 30 seconds and requires no signup or payment.