How to Block Pop-Ups and Pop-Unders

Pop-ups were supposed to die in the late 2000s when browsers started blocking new windows opened without a user click. They did not die. They evolved. In 2026 the "pop-up" category covers at least four distinct annoyances, and the worst offenders are the newer ones browsers do not block by default.

This guide explains what each kind of pop-up is, why it exists, and how to make sure it never reaches your screen again. For the bigger picture, see how ad blockers work and our best ad blocker 2026 round-up.

The four kinds of "pop-up" in 2026

1. Classic pop-up windows

A new browser window or tab opens, usually with an ad. Modern browsers block these when they are not triggered by an explicit user click. Mostly a solved problem since the late 2000s.

2. Pop-unders

The same as pop-ups, except the new window opens beneath your current one. You only notice it when you close the active window and find an ad waiting underneath. Browsers have largely closed this hole, but a long tail of sites still use it via creative event chaining.

3. Overlay interstitials

In-page modals that cover the article and demand interaction. Newsletter signups, "subscribe to read", autoplay video pop-ins, full-screen ads. Technically not browser pop-ups, so browser pop-up settings do not touch them. They are the most common annoyance in 2026.

4. Notification permission prompts

The browser's own UI asking whether you want notifications from a site. Not malicious on its own, but most sites overuse it. Modern browsers gate this behind user interaction, but the prompts still leak.

A good blocker handles all four.

How browsers handle pop-ups out of the box

Chromium browsers and Firefox both block window.open calls that are not triggered by a direct user click. They also block "abusive ads" patterns flagged in Google's Better Ads Standards. This is enough to stop the most obvious offenders but leaves a wide gap.

The browser's own pop-up settings live under Settings, Privacy and Security, Site Settings, Pop-ups and Redirects. Defaults are usually correct; toggle them to "Blocked" if not.

How a blocker improves on the default

Ad blockers add four layers on top of the browser's default behaviour.

1. Network-level blocking of pop-up scripts. Most pop-up campaigns are loaded by a small set of identifiable third-party scripts. Blocking those scripts at the network level stops the pop-up from ever being attempted.
2. window.open interception. A small content script wraps window.open and refuses to honour calls coming from known ad domains or matching known pop-up patterns.
3. Cosmetic removal of in-page modals. Newsletter pop-ups, paywall walls, and autoplay video overlays are matched by CSS selectors and hidden before they have a chance to render.
4. Annoyance lists. A growing community-maintained list of selectors and rules for the specific modal patterns sites overuse.

NovaBlock ships all four out of the box.

Setup

If you already use NovaBlock, you are done. Pop-up and overlay handling is on by default.

If you do not:

1. Install NovaBlock from the Chrome Web Store or Firefox Add-ons.
2. Pin the icon. The popup will show you what was blocked per site.
3. Do not change anything else. Defaults are tuned for the median user.

If you use another blocker, check that its annoyances list is enabled. Most blockers ship it but leave it off by default.

Comparison

Why pop-unders are still around

Pop-unders are extremely cheap to serve and pay decent ad-network rates per impression because the user "saw" the ad even if they did not engage. Lower-quality publishers still use them because the alternative, less ad revenue, is worse for their business model.

The publishers running pop-unders in 2026 are mostly sites you would not visit deliberately: pirated content aggregators, low-quality content farms, certain torrent sites. Mainstream publishers have moved on. If you encounter a pop-under in 2026, it is a smell. Your blocker should silence it, but the site itself is worth inspecting.

Why overlay interstitials are everywhere

This one is not malice; it is conversion optimisation. Newsletter modals, "create a free account to continue", "download our app", autoplay video pop-ins. They exist because a small percentage of users click them, and that percentage justifies the experience for everyone else.

A good blocker treats these as annoyances and removes them. The site still works; the modal is just gone.

Pros and cons

Pros

• Cleaner browsing. You read the article you came to read.
• Less risk of accidental click-through to a malicious site.
• Less mobile data, less battery use, less cognitive load.

Cons

• A small number of paywalls hide their "subscribe" button behind a modal that gets hidden. You may need to pause the blocker on those sites if you want to subscribe.
• Some genuine in-app prompts (like "your file is ready to download" toasts) sometimes get caught by overzealous annoyance rules. Reporting these via the blocker's popup gets them fixed.

Troubleshooting

• Pop-up still appears. Update the blocker. If it persists, report the site via the popup so we can add the rule.
• A site you want to interact with has its modal hidden. Pause NovaBlock for that site; the modal returns.
• The browser's own pop-up blocker keeps triggering on a legitimate workflow (file downloads, login flows). Check the Chrome address bar for the "pop-up blocked" icon and allow the specific site once.

Conclusion

Pop-ups are a category, not a single thing. Browsers handle the simplest cases out of the box and leave the rest to the user. A dedicated blocker fills the gap and removes the in-page modals, overlay interstitials and pop-under variants that have replaced the classic 2005 pop-up. NovaBlock ships all of that on by default. Install from the Chrome Web Store and your browsing instantly gets quieter. For more on the related annoyances category, the remove cookie banners guide is a good follow-up.