The private grammar checker for 21st Century English
Users
60K
+10K in 30 days
Rating
4.2 / 5
+0.03 in 30 days
Ratings
128
+9 in 30 days
Store rank
#3,093
#2,710 among extensions
Version
2.12.0
updated 2 Oct 2026
Users
monthly, 18 months
Latest, 15 Oct 2026:60,000 usersMove the mouse over the chart for any month
Ratings count
monthly, 18 months
Latest, 15 Oct 2026:128 ratingsMove the mouse over the chart for any month
The Chrome Web Store rounds user counts down to the leading digit, so the user line moves in steps. The ratings count is exact and is the better signal of real adoption.
About Private Grammar Checker - Harper
Harper is an English grammar checker designed to be just right. I created it after years of dealing with the shortcomings of the competition.
Grammarly was too expensive and too overbearing. Its suggestions lacked context, and were often just plain wrong. Not to mention: it's a privacy nightmare. Everything you write with Grammarly is sent to their servers. Their privacy policy claims they don't sell the data, but that doesn't mean they don't use it to train large language models and god knows what else. Not only that, but the round-trip-time of the network request makes revising your work all the more tedious.
LanguageTool is great, if you have gigabytes of RAM to spare and are willing to download the ~16GB n-gram dataset. Besides the memory requirements, I found LanguageTool too slow: it would take several seconds to lint even a moderate-size document.
That's why I created Harper: it is the grammar checker that fits my needs. Not only does it take milliseconds to lint a document, take less than 1/50th of LanguageTool's memory footprint, but it is also completely private. That's the power of open source.
Growth
Window
Users
Change
Ratings
Rating
7 days
0
+0.0%
0
+0.04
30 days
+10K
+20.0%
+9
+0.03
6 months
+30K
+100.0%
+47
+0.13
1 year
+53K
+757.1%
+113
−0.33
Chrome Web Store search rankings
Where Private Grammar Checker - Harper appears when people search the store, with the 30 day change