Anti-Grammarly AI Tool Adds Typos to Emails to Make Them Appear Human-Written

Anti-Grammarly Browser Plugin Intentionally Adds Typos to AI-Generated Emails

A new AI tool is challenging decades of digital communication norms by deliberately introducing imperfections into writing. Called Sinceerly, this browser plugin functions as an anti-Grammarly, intentionally adding typos to emails to make AI-generated text appear more human 1

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. Created by Ben Horwitz, a Harvard Business School MBA student and investment partner at venture capital firm Dorm Room, the tool was coded using Anthropic's Claude AI 2

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The software promises to eliminate telltale signs of AI composition from emails with features like "Kill the emdash! No more 'not just...'! Add some typos!" 1

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. Users can select from three severity settings: "Subtle," "Human," and "CEO"—a tongue-in-cheek reference to how little care high-ranking executives often put into their communications 2

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. The tool goes as far as undoing capitalization at sentence beginnings and appending phrases like "sent from my iPhone" to enhance believability.

How Flawless Writing Became a Red Flag in Digital Communication

The emergence of this anti-Grammarly reflects a fundamental shift in how polished writing is perceived. For years, tools like Grammarly helped eliminate errors and improve clarity. But in the age of generative AI, flawless writing has started to carry a different implication—it often signals that a machine may have written it 3

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. Perfect grammar, once a marker of professionalism, can now feel artificial and raise suspicion about authenticity.

"My email inbox is filled with AI slop," Horwitz told Business Insider, explaining his motivation for creating the tool 2

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. He tested Sinceerly by cold emailing five Fortune 500 CEOs, and four replied—each response under ten words, with two containing typos 2

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. This real-world experiment underscores how imperfection has become a marker of human authenticity in professional communication.

Satire or Serious Solution to AI Writing Tropes?

When asked whether the project was serious, Horwitz clarified that it's "tongue-in-cheek" and "closer to satire" 1

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. The deadpan website presentation makes people do a double-take, which is precisely the point—to make users think twice about their reliance on AI writing tools. However, the irony runs deeper. The tool uses AI to correct mistakes made by another AI, creating a scenario where LLMs are deployed to hide LLM usage 1

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Despite its satirical origins, some users may adopt it seriously. As one writer noted, typos that once signaled carelessness or unprofessionalism are now "signatures of our humanity" that demonstrate actual care rather than mindless reliance on an LLM 4

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. This inversion is significant—AI isn't just changing how we write, but what "good writing" even means 3

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What This Means for Trust and the Future of AI Writing

This trend toward intentional imperfection raises questions about trust in digital communication. If both polished and imperfect writing can be generated by AI tools, distinguishing between human and machine becomes increasingly difficult 3

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. Users may find themselves adjusting their tone—intentionally or not—to appear more genuine, incorporating shorter sentences, casual phrasing, or minor errors into professional emails.

The evolution suggests that future AI writing tools will shift focus from correctness to believability, adapting tone, style, and even mistakes based on context and audience 3

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. The goal will be making communication feel natural rather than flawless. For everyday users, this could subtly change how emails are written and interpreted, with perfect grammar increasingly signaling automation rather than competence. Watch for how organizations and individuals navigate this new landscape where adds typos on purpose becomes a strategy to make AI text appear human, fundamentally altering expectations around professional digital communication.