A surprising number of free programs, particularly ones distributed through third-party download sites, arrive wrapped in an installer that also tries to install browser toolbars, changes your default search engine, or bundles entirely unrelated "optional" software. This is bundled adware, and it's one of the most common ways an otherwise healthy PC ends up slow and cluttered with pop-ups.
Key takeaway: Bundled adware almost always arrives through the installer itself, hidden behind pre-ticked checkboxes on "Custom" or "Advanced" install screens — reading every screen carefully is the single most effective defence.
How bundled adware actually gets installed
It's rarely hidden or forced on you outright; it's usually offered legally, buried in the installer's terms, with a checkbox pre-ticked to opt you in by default. Clicking through an installer quickly, accepting every default, is exactly how a browser toolbar or a "PC optimiser" you never wanted ends up installed alongside the program you actually meant to get.
How to spot it during installation
- Always choose "Custom" or "Advanced" install rather than "Express" or "Quick" when an installer offers the choice — it reveals what else is bundled.
- Read every screen of the installer, not just the first, since bundled offers often appear on a later screen after the main licence agreement.
- Untick any checkbox for a second program, browser extension, toolbar, or "recommended" tool you did not specifically go looking for.
- Watch for pre-checked boxes to change your default browser, search engine, or homepage — these are almost never things you actually want.
- If an installer seems unusually pushy or has several extra screens trying to install unrelated software, consider cancelling and finding the program from a more reputable source instead.
Tip: Tools like Ninite (covered in our Open-Source Basics section) sidestep this problem entirely by fetching clean, standard installers directly from developers, with no bundled offers at all.
Where you're most likely to encounter it
Bundled adware is most common on general "download free software" websites that host installers for many different programs, rather than linking to the developer's own site. It's much less common — though not impossible — when downloading directly from a program's official website, the Microsoft Store, or a well-known open-source project's own release page.
Before you start: Search for "[program name] official download" rather than just "[program name] download" — this makes it far more likely the first search result is the developer's own site rather than a third-party aggregator.
What to do if you've already installed something unwanted
Go to Windows Settings > Apps > Installed apps, sort by install date, and uninstall anything unfamiliar that appeared around the same time as the program you actually wanted. Then check your browser's extensions list and reset your default search engine and homepage if they've changed. A free malware scanner (see our related article on free second-opinion scanners) can also catch adware that a standard antivirus sometimes misses.
Reputable sources for common free software
- The software developer's own official website, whenever you can identify it directly.
- Microsoft Store, for Windows-native apps.
- Ninite.com, for one-click clean installs of dozens of popular free programs.
- GitHub's official "Releases" page, for open-source software distributed there.
| Warning sign | What it usually means |
|---|---|
| "Express" install pre-selected | Hides what's actually being installed |
| Pre-ticked checkbox for another app | Bundled software, opt-out required |
| Offer to change default browser/search | Adware-adjacent behaviour, always decline |
Frequently asked questions
- Is bundled adware actually harmful, or just annoying?
- Often it's more intrusive than dangerous — extra toolbars and pop-ups — but some bundled tools track browsing behaviour or make your PC noticeably slower, so it's worth avoiding either way.
- Does antivirus software stop bundled adware automatically?
- Not always. Because it's technically installed with a form of consent (the ticked checkbox), many antivirus tools classify it as a "potentially unwanted program" rather than a threat, and won't block it outright.
- Is it safe to download from well-known sites like CNET's Download.com or Softonic?
- These sites have had bundling issues in the past; going straight to the developer's own official site is generally safer whenever that's practical.