Do you want to block a specific website so it doesn't distract you while you're working? Or do you want to limit access to inappropriate websites? You can block websites on Android either with or without a dedicated app, and we'll show you how to do both.

Block websites on Android with a third-party app
An easy way to block a website on your Android phone is by using a free website blocking app. One such app is BlockSite (free but ad-supported), which allows you to restrict access to your specified websites at the specified time in your browsers.
Once you block a website with this app, that website is not accessible in any of your web browsers. Later, you can unblock a website if you want.
To use this method, download and install the free BlockSite app on your phone. Then, launch the app and grant the app all the permissions it needs.
When you reach the main screen of the app, select “Blocklist” followed by the “+” (plus) button.

On the “Add Sites/Apps” screen, at the top, tap the text field and type the URL of the website you want to block. For example, to block wikipedia.org, type wikipedia.org in the text field, and then select the website from the list. You can add multiple websites here to block them on your phone.
After you specify the websites, in the top right corner of the app, tap “Done.”

Select “Done” in the message.

You've successfully specified the websites you want to block, but your websites aren't blocked yet. This is because you need to set a schedule for when the block will take effect .
To do this, on the app's main screen, tap “Schedule.”

Select the days and times you want your designated websites to remain blocked. To block them indefinitely, select the “Full Week” and “All Day Long” options.
Then, next to “Select All,” enable the option.

And you're done with your settings. Your designated websites are no longer accessible in your phone's web browsers. If you try to access one of these websites, you'll see a message from BlockSite instead of the actual website content.

Block a website on Android without an app
If you don't want to use a third-party app to block sites on your Android phone, you can either restrict access to a site within Mozilla Firefox or set a blanket ban on adult sites using custom DNS servers.
Use an add-on in Mozilla Firefox
If you use Firefox as your primary web browser, a free add-on will restrict access to specific websites in your browser. Note that using this method only blocks your websites in Firefox. Your other browsers will still be able to access your blocked websites.
To use this method, launch Firefox on your phone. Then, tap the three dots in the top right corner and select “Add-Ons.”

On the “Add-Ons” page, next to the “LeechBlock NG” add-on, click the “+” (plus) option.

In the lower right corner of the open prompt, tap “Add.”

When the add-on is installed, select “Okay, Got It.”

Access Firefox's “Add-Ons” page by clicking the three dots in the upper-right corner of the browser and selecting “Add-Ons.”
Then, tap “LeechBlock NG”.

Select “Settings.”

Tap the large text field and enter the website URLs you want to block. Set the time frame for when those websites will remain blocked.
Then, scroll down the page and click “Save Options & Close.”

And you are ready.
From now on, when you try to access a restricted website, Firefox will not load the website for you.
Use custom DNS Servers to block adult sites
If you want to set a blanket ban on websites containing adult content, pirated media, and malware on your Android phone, use OpenDNS's free FamilyShield DNS servers. These servers ensure that your phone doesn't load such websites on your local network.
To get started, launch the Settings app on your Android phone. The exact steps for performing the following procedure vary depending on your phone model.
In Settings, go to Connections > Wi-Fi.

Next to the Wi-Fi network you're connected to, tap the gear icon.

On the screen that opens, tap “View More.” Then, select the “IP Settings” option and select “Static.”
In the “DNS 1” field, enter the following:

Tap the “DNS 2” field and enter the following.

At the bottom, click “Save” to save your changes.

Your custom DNS servers will now block access to adult websites and other unsafe content on your Android phone.
Information source: howtogeek.com
