01
Find the file and copy it
The hosts file is a plain text file without an extension. Windows protects it, so copy it to the desktop, edit the copy and write it back.
%SystemRoot%\ystem32\rivers\tc\ostsAdd lines of the form **0.0.0.0 domain.tld** to the hosts file in **drivers\tc**, keep a backup, and clear the DNS cache afterwards. It blocks by name only, so a hardcoded IP is unaffected.
Requirements
- Admin rights
- A text editor
- Twenty minutes
Instructions
02
Learn the format before adding lines
Each line starts with an address, then one or more names, separated by spaces. Comments start with a hash. A wrong separator turns the line into a comment or an error.
0.0.0.0 ads.example.comtipUse 0.0.0.0 rather than 127.0.0.1 for ad hosts. A local web server otherwise answers the request and the page waits.
03
Add only what you can explain
A curated list of a few dozen domains is maintainable. A downloaded list with a hundred thousand entries slows every name lookup and breaks services you use.
⚠ warningBlocking a shared content domain takes the whole site with it. When a page stops loading images, check the list before blaming the browser.
04
Save with the right encoding
Notepad saves UTF-8 by default, which is fine. The file must keep the name hosts with no extension; a hosts.txt file is ignored completely.
05
Flush the DNS cache
Windows caches resolved names. Without a flush the new entries apply only after the cache expires, which looks like the edit did nothing.
ipconfig /flushdns
06
Keep the backup next to the file
A hosts file that breaks a sign-in page is a five-second fix with a backup. Store the original as hosts.bak and swap it back when something misbehaves.
copy hosts hosts.bakCommon issues
The file will not save
The editor is not elevated. Open it as administrator or edit a copy and copy it back.
Nothing is blocked
The file has an extension, the cache was not flushed, or the site uses a different domain.
A website broke
A shared content domain is on the list. Remove that line and flush again.
Everything is slow
A very large list. Cut it down to what you actually need.
Frequently asked
Does this block ads inside apps?
Only if those apps use DNS names and do not fall back to hardcoded addresses.
Does it survive updates?
Yes. Windows does not reset the hosts file unless a third-party tool rewrites it.
How to undo this
Restore **hosts.bak** over the hosts file, or delete your added lines and run **ipconfig /flushdns**. All lookups return to normal.
Changelog · 1 entry
- 2026-10-31First version
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