One of Otto's core features is Website Blocking. This page explains how to use Focus Session Blocking.

How does it work?
Any website added to the focus session blocklist will be blocked during all focus sessions, including task sessions. On the free version, you can add up to 4 websites.
You can either enter websites manually in the dialog box or select from the preset list.
By default, all websites are unblocked during break sessions. To block them, read more about it at the bottom of this page.
How to add websites to the blocklist
Step 1. Open the Otto Chrome extension
Click the Otto extension icon to open the main menu.

Step 2. Access the blocking section
- Click the block icon (the 3rd button in the navigation bar).
- Make sure the "Blocklist" tab is selected.

Step 3. Open block management
- Click "Create and Manage Focus Blocks" to open the settings page.
- Click the "Add+" button to open the dialog box.

Step 4. Add websites
- Enter a website URL in the input field, then click "Add" or press Enter.
- Or select a website from the preset list.
- Click "Save" when you're done.
Enable blocking during break sessions
By default, all websites are unblocked during break sessions. You can change this by going to settings and turning on the break block option.
Advanced Blocking Options
Read more about it on How to block specific URLs only
There are other blocking modes too: Scheduled Block and Autoblock
