Harvard student builds Chrome extension to humanise AI emails

A Harvard student has built a Chrome extension that does the opposite of every writing tool that came before it, and it may say more about where workplace communication is heading than any productivity app released this year.

Sincerly is an online service that takes high-quality AI text and messes it up deliberately with the aim of making it look as if written by a human hand.

Sincerely was created by Ben Horwitz, using Claude AI, a product by Anthropic. The reason for creating 'Sincerely' was simple but something most people can relate to when receiving emails. "I was so sick of AI slop in my own inbox," Horwitz said on the TBPN podcast. "People would email me; it all looks the exact same."

This extension is free for some initial uses before requiring $4.99 for further use, but according to Horwitz, this product is unlikely to be his main income source, since he views it more as a piece of social commentary rather than a tool.

There are three kinds of settings provided by Sinceerly that are designed according to a particular type of flaw. There is an option called 'Subtle' where all unnecessary words are eliminated, some of the phrases are converted into contractions, and in the first line, a mistake will be made intentionally.

However, the Human mode will make the writing conversational while implementing the above alterations as well. In the third choice, which is called the 'CEO mode', the whole message will be written in lowercase, and only the necessary information will remain. Even if the email lacks a signature, then "sent from my iPhone" will be added.

Horwitz identified something genuinely strange about how people are using the tool in practice. "People are copy-pasting; first they're prompting, then they're copy-pasting their prompt into email, and then they're using 'Sincerely' to make their email not sound like AI," he said. "Humans using AI to make AI more human."

That loop prompt, generate, and humanise reflects a communication arms race that neither side of the inbox fully controls anymore.