For San Francisco-based Grammarly Inc., correcting spelling and grammar mistakes is big business.

The startup, whose namesake writing assistant boasts more than 20 million daily users, today revealed that it has raised a $90 million funding round led by General Catalyst. Institutional Venture Partners and a number of other backers who weren’t named contributed as well. 

The round marks the latest milestone in Grammarly’s somewhat unusual path to mainstay productivity tool status. The startup, which launched a decade ago in Kiev, Ukraine, raised its first round of funding only three years ago from a consortium also led by General Catalyst. Even more notable is that Grammarly has been profitable since 2011, which puts it in stark contrast with other heavily funded productivity startups such as Monday.com Ltd.

The startup managed to stay out of the red even as it tripled its user base in the three years since that first funding round. Grammarly’s growth is the fruit of aggressive marketing investments and a feature development roadmap that has taken the service far beyond its spell-checker roots.

Grammarly uses machine learning algorithms to flag poor word choices, punctuation issues, unclear phrases and other errors that might detract from the content of an email or document. A recently added tone detector also shows users how the text will sound to the reader.

As the core feature set has expanded over the years, so has product availability. Grammarly offers the service in the form of extensions for all the major browsers, iOS and Android apps and an Office 365 add-on.

Most of the startup’s users rely on the free version of its service, but it also provides premium subscription tiers that are gaining traction in the enterprise. Its Grammarly Business product is used by teams at companies such as Dell Technologies Inc., Cisco Systems Inc. and Expedia Group Inc. among others. The startup plans to double down on this market using the new funding by developing more features for organizations. 

Grammarly has raised $200 million in outside capital to date.

Photo: Grammarly