Sinceerly, a browser extension for Gmail, claims it can undo your AI writing—essentially "humanizing" text generated by large language models to make it sound less robotic. The tool launched this week and operates directly inside Google's email compose window as a Chrome extension. Founder Ben built the product after growing frustrated with the homogenized, corporate-speak flooding his inbox from AI-assisted correspondents.

How It Works

The process is straightforward: users draft an email (AI-generated or otherwise), click the Sinceerly icon in their Gmail compose window, and hit "humanize." The tool then rewrites the text while removing common LLM tells—emdashes that scream artificial intelligence, repetitive filler phrases like "not just," and robotic sentence structures. A yellow highlighting system shows every change made, allowing users to approve or reject modifications before inserting the revised version.

Pricing Tiers

Sinceerly offers three tiers: a free option providing three email rewrites per month with access to all intensity levels, a $4.99/month Pro plan for unlimited rewrites with cached results and instant switching between intensity settings, and a Bring Your Own API Key (BYOK) option for users with Anthropic keys who prefer paying only for actual usage. The BYOK model ensures email text and API keys aren't retained on Sinceerly's servers—all processing happens locally in the browser.

The Humanization Paradox

Here's where it gets interesting from an insider perspective: we're now in an arms race between AI writing tools and anti-AI writing tools. OpenAI, Anthropic, Google, and Meta have all shipped increasingly sophisticated models that produce more natural-sounding output, while companies like Sinceerly are simultaneously building products to strip away the artificial characteristics those same models generate. The founder's own testing methodology—cold emailing Fortune 500 CEOs with humanized AI content and measuring reply rates—suggests there's genuine demand from professionals who want the efficiency of AI assistance without the telltale fingerprints.

Privacy Considerations

The extension claims all requests travel over HTTPS, emails aren't logged or retained, BYOK API keys stay browser-side only, and the service only processes text users actively choose to humanize. For privacy-conscious developers tired of corporate-speak saturating professional communication channels, this architecture addresses major concerns around data exposure.

Key Takeaways

  • Sinceerly is a Gmail Chrome extension that rewrites AI-generated emails to sound more natural
  • Free tier offers 3 monthly rewrites; Pro costs $4.99/month for unlimited access
  • BYOK option lets users plug in their own Anthropic API key for pay-per-use flexibility
  • The tool targets specific LLM tells: emdashes, filler phrases like "not just," and robotic structures

The Bottom Line

We're watching the commoditization of AI detection resistance unfold in real-time. When every professional's inbox sounds generated because everyone's using the same handful of models, tools like Sinceerly fill a genuine market gap—but they also underscore how homogeneous AI-generated prose has become. The irony is thick: paying monthly to make your AI slop pass as human-written content.