To block sites in incognito mode, you need a blocker that works below the browser, not inside it. Many browser extensions stay off in private windows unless you turn them on. That means a private tab can open a site the extension would block. A DNS blocker filters the step where your device looks up a website's address. Private tabs do that lookup too, so the block holds in every tab, browser, and app.
In short
Many browser extensions don't run in private windows by default, so incognito tabs can skip them.
Private browsing hides your history on the device. It doesn't hide the website lookup.
A DNS blocker filters that lookup, so blocks apply in private tabs, every browser, and every app.
No blocker is perfect, so pair the block with a partner who knows when protection turns off.
Why does a website blocker fail in incognito mode?
Most people meet blocking through a browser extension. You install it, add a few sites, and it works. Then one night you open a private window and the site loads anyway.
That happens because of where the extension lives. An extension is a small program that runs inside one browser. Browsers often treat private windows as a separate space, and many extensions don't run there unless you go into the browser's settings and allow it. Even when you allow it, the extension covers only that one browser. Open a different browser, or tap a link inside an app, and you're outside its reach.
Blocks that you set inside a single app have the same problem. They guard one door, and a phone or a Mac has many doors. Private mode is one of the easiest to find, especially late at night when your plan from earlier in the day feels far away.
Apple's built-in Screen Time tools work at a different level than extensions, and they help a lot of people. How they handle private tabs, other browsers, and in-app browsers can vary, so test the sites you care about on your own device before you rely on them. If you want the full rundown of options on a phone, see how to block websites on iPhone.
What does private browsing actually hide?
Private browsing is a privacy feature, not an invisibility feature. It's useful to know what it does and doesn't do.
When you close a private tab, the browser forgets:
- the pages you visited in that tab,
- the cookies and site logins from that session,
- what you typed into forms and search boxes.
What private browsing does not change is how your device reaches a website. To load any page, your device first has to turn the name you typed into an address it can connect to. That lookup is DNS (the internet's address book, which matches a name like example.com to a numeric address). A private tab still asks for that address the same way a normal tab does.
This is the opening a DNS blocker uses. It doesn't need to see inside the browser or know which kind of tab you're in. It answers the address lookup, and if the site is on your blocklist, the lookup goes nowhere.
How does DNS blocking cover private tabs?
A DNS blocker sits between your device and the address book. Every app and every browser on the device sends its lookups through it. When a lookup matches a site on your blocklist, the blocker refuses to hand back a working address, and the page can't load.
Because the filter works at the device level, a few things follow:
- Private tabs are covered. The lookup happens before the browser decides whether to save history, so incognito makes no difference.
- Every browser is covered. Switching from Safari to another browser doesn't get around it.
- Apps are covered. Links that open inside social apps, mail, or messaging apps go through the same lookup.
That's the main reason people choose DNS blocking when private mode keeps winning. You set the block once, and it applies everywhere on that device. If you want the deeper version of how this works on iPhone and Mac, read what a DNS blocker is and how it works.
Blockd uses this approach. It filters at the DNS level, so blocks apply in every app and browser, not only Safari, and switching browsers does not get around it. That includes private tabs on iPhone and on Mac.
What can't a DNS blocker do?
It's worth being honest about the gaps, because a tool you think is airtight makes it easy to stop paying attention.
- It decides by address, not content. DNS blocking can't see what's on a page. It blocks a site by its name. It also doesn't take screenshots.
- One VPN at a time on iPhone. iPhone runs one VPN (a connection that routes your traffic through a separate service) at a time. If you connect another VPN app, it can replace Blockd's connection. If your blocker seems to turn off by itself, that's a common cause, and why your blocker keeps turning off on iPhone covers it.
- Some apps bring their own DNS. Apps that use their own hard-coded DNS can get around DNS filtering.
- You can always turn it off. Any blocker can be turned off by the person who installed it. Blockd doesn't try to make that impossible.
That last point is why a partner matters. Blockd makes turning protection off visible. If protection turns off, your partner gets an alert within seconds. If the app is deleted, your partner is alerted within minutes, once the device goes quiet. The block handles the common cases, and the partner covers the moments when you'd reach for the off switch.
How do you set up blocking that covers incognito tabs?
You don't need a complicated setup. Start small and test it.
- Pick the sites that matter most. Write down the two or three sites you open in private tabs. Start there.
- Use a device-level blocker. Choose a DNS blocker instead of a browser extension, so the block applies to private tabs and every browser.
- Test it in a private tab. Open a private window, type one of your blocked sites, and confirm it doesn't load. Then try a second browser and a link inside an app.
- Cover each device. A block on your phone doesn't cover your laptop. Set it up on every device you use.
- Add a partner. Choose someone steady and calm, and agree on what they'll see. A short weekly check-in works for many people.
Then leave it alone for a week and see what happens. If you find yourself working around it, notice how. That pattern tells you which gap to close next, or which conversation to have with your partner.