Thousands of users, hundres of reviews and 4.5/5 on the Chrome store. Here are some positive reviews by Otto's users.
Otto is so good, I have adhd and it really helps me lock in!
by Ayesha, 5 stars
Great app to avoid the dark side of the bright web
by Matteo, 5 stars
Otto works great for me overall--when I remember to use it. When the focus session ends, it's impossible to ignore--you either take a break or extend the focus session.
by Clarissa, 4 stars
Otto works really well for its intended purpose, and it's helping me fight my internet addiction and make better use of my time. The UI is very simple and clean, and the illustrations are adorable. It's very helpful all around!
by Hannah, 5 stars
Works well for its intended use - no complaints!
by Greg, 5 stars
I love the simplicity of the app, making focusing and time management easily to apply and sustain in time.
by Nicolas, 5 stars
If I could give it more than 5 stars I would! I love how it blocks websites. I have a problem with getting on social media so this has helped so much
by Kennedy, 5 stars
great simple app i do like the game-like aspects and overall helps with adhd 10/10
by Jude, 5 stars
It's so good for me, an ADHD person
by Lam, 5 stars
Its a really good extension for blocking out distraction and it works
by Nafil, 4 stars
After using this for a couple months, I really don't have anything negative to say about it. Otto does exactly what it is designed to do, block distractions and help you be more productive. Even without the upgrade, it still works well to boost productivity.
by Joel, 4 stars
Simple but effective. Easy to customise, nice passive incentives. It does exactly what you're asking of it and it does it well.
by Uriel, 5 stars
The best pomodoro+website blocker i have used! this has helped me become so much more productive and is well designed.
by Mihika, 5 stars