Undetectable AI’s Cover Letter Generator vs. Grammarly’s AI Detector

Not every AI tool is built to write your next viral blog post. Some just want to help you get hired. This is Undetectable AI’s cover letter generator vs. Grammarly’s AI detector.

John Angelo Yap

Updated July 23, 2025

A robot getting asked about their authenticity during a job interview, generated with ChatGPT

A robot getting asked about their authenticity during a job interview, generated with ChatGPT

Reading Time: 4 minutes

Undetectable AI's Cover Letter Generator, like most of their tools, isn’t trying to impress you with flashy language or clever turns of phrase. It’s focused on one thing: helping you get past the first round of filters — including, sometimes, other AI tools built to sniff out whether you used AI in the first place.

Grammarly, on the other hand, is best known for grammar fixes and sentence polishing. But recently, they’ve expanded into AI detection. That means we’ve reached a strange moment where one AI tool is generating your job application, and another is judging whether it feels “too” generated.

So how do these tools stack up when used in the same workflow? Let’s take a closer look. 

What is Undetectable AI?

Undetectable AI is a tool designed to make AI-generated content sound human.

It focuses on rewriting content to bypass detection tools — the ones that flag overly robotic phrasing or suspiciously perfect grammar. Where most AI tools aim for speed or tone, Undetectable AI aims for believability.

It’s used by students, marketers, freelance writers, and now, job seekers. The goal is simple: use the speed of AI without getting flagged for it.

Recently, it introduced a feature specifically for people applying to jobs — and that’s where the Cover Letter Generator comes in.

What is Undetectable AI's Cover Letter Generator?

The Cover Letter Generator is straightforward. You paste in your resume, details about the job, and maybe a blurb or two about your experience — and it spits out a clean, human-sounding cover letter.

The key difference is that the output is designed to avoid sounding like AI wrote it.

The writing intentionally avoids common AI giveaways like “I am thrilled to apply…” or “With a proven track record…” Instead, it leans into natural phrasing, such as: “I’ve spent the past few years doing [X], and this role feels like the next step.”

It’s built with job boards and recruiters in mind. The kind of cover letter that won’t raise red flags with AI detectors — or real people.

What is Grammarly?

Grammarly has been around forever in the internet years. What started as a grammar checker is now a full writing assistant — suggesting rewrites, changing tone, and offering AI-generated content in real-time.

But in the middle of all those updates, Grammarly also introduced something else: its own AI detector.

What is Grammarly's AI Detector?

Grammarly's AI Detector is exactly what it sounds like — a tool that guesses whether a piece of writing was AI-generated.

It’s not super detailed. You paste in your text and get a short verdict, usually something like “Sounds human” or “Likely AI.”

It’s quick, and it works okay if you’re looking at straight-from-ChatGPT content. But the moment that writing gets cleaned up or stylized — especially by a humanizer like Undetectable AI — Grammarly tends to miss.

Still, it’s built into the Grammarly ecosystem. So if you’re already using it for editing, it’s an easy way to double-check your own output.

Undetectable AI’s Cover Letter Generator vs. Grammarly’s AI Detector

Test #1

Undetectable AI: Doesn’t pass the AI detection test.
AI Likelihood Score: 100%

Test #2

Undetectable AI: Passes the AI detection test.
AI Likelihood Score: 12%

Test #3

Undetectable AI: Grammarly AI Detector is confused!
AI Likelihood Score: 50%

Test #4

Undetectable AI: Passes the AI detection test.
AI Likelihood Score: 0%

Test #5

Undetectable AI: Passes the AI detection test.
AI Likelihood Score: 25%

Overall Score

Test Number

Undetectable AI vs. Grammarly AI Detector

#1

100%

#2

12%

#3

50%

#4

0%

#5

25%

Score

37.4%

The Bottom Line

Undetectable AI’s Cover Letter Generator isn’t trying to reinvent the cover letter. It’s just trying to make it human-sounding and tailored — fast. And based on the test scores, it does that job pretty well.

Grammarly’s AI Detector, meanwhile, plays the role of gatekeeper. It’s a little decent at catching obvious AI content, but struggles when that content’s been rewritten to sound more natural, which is Undetectable AI’s forte.

If you’re using AI to help you apply to jobs, this matchup matters. The last thing you want is to get filtered out for using a tool that’s supposed to help.

So far? Undetectable AI is ahead in the one area that counts: staying undetected. And for job seekers trying to cut through the noise, that edge makes a difference.

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Written by John Angelo Yap

Hi, I'm Angelo. I'm currently an undergraduate student studying Software Engineering. Now, you might be wondering, what is a computer science student doing writing for Gold Penguin? I took up studying computer science because it was practical and because I was good at it. But, if I had the chance, I'd be writing for a career. Building worlds and adjectivizing nouns for no other reason other than they sound good. And that's why I'm here.

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