Where apps hide your files

The hosts file: location, editing, DNS flush

Updated 2026-10-28 · 5 min read

The hosts file is /etc/hosts, a small text file that maps names to addresses before DNS is asked. It needs administrator rights to change, so back it up first, and a changed entry may not apply until you flush the DNS cache.

The location

/etc/hosts

/etc is a link to /private/etc, so /private/etc/hosts is the same file. On the Mac used for this guide it is owned by root, readable by everyone and writable only by root.

Finder hides /etc. To open its folder, choose Go > Go to Folder (⇧⌘G), type /etc and press Return, or reveal the file from Terminal:

open -R /etc/hosts

To read it, which changes nothing:

cat /etc/hosts

What the stock file contains

On a Mac that nobody has edited, the file is a short comment header (it starts # Host Database and warns not to change the localhost entry) followed by three working lines:

127.0.0.1	localhost
255.255.255.255	broadcasthost
::1             localhost

Leave those three lines alone; software on your Mac relies on localhost reaching the loopback address. Each line is an address, whitespace, then one or more names. A # starts a comment.

Back it up first

Before any edit, copy the current file into your home folder. This needs no administrator rights and changes nothing in /etc:

cp /etc/hosts ~/hosts.backup

Edit it

TextEdit cannot save to /etc directly, so use Terminal and sudo:

sudo nano /etc/hosts

Enter your Mac password (nothing appears as you type). On recent macOS nano is a link to the pico editor that ships with the system, which uses the same keys. Use the arrow keys to go to the bottom, add your line, press ⌃O then Return to save, and ⌃X to exit. Examples:

127.0.0.1   example-site.test
10.0.0.25   staging.internal
0.0.0.0     ads.example.com

The first points a name at your own Mac for local development, the second maps a name to a server, and the third blocks a domain by sending it to an address that goes nowhere. Use your own names, one entry per line, and put a comment above each block you add (# dev sites) so you can find it later.

Flush the DNS cache

macOS caches name lookups, so an edit may seem to do nothing at first. The reset used across recent macOS versions is:

sudo dscacheutil -flushcache; sudo killall -HUP mDNSResponder

It prints nothing when it works. Apple does not publish this as an official command for each release, but the pair is the standard answer for Sonoma and Sequoia, and running it is harmless. Browsers keep their own cache too: Chrome's can be cleared from its chrome://net-internals/#dns page, and quitting and reopening a browser clears the rest. A VPN, or DNS over HTTPS in a browser's settings, can bypass the hosts file entirely.

Check that it worked

To list only the active lines, skipping comments and blank lines:

grep -v '^#' /etc/hosts | grep .

To see how your Mac now resolves a name, ask the system resolver, which reads the hosts file:

dscacheutil -q host -a name example-site.test

ping also goes through the system resolver. dig and nslookup query a DNS server directly and ignore the hosts file, so they will not show your entry even when it works.

Common problems

• "Permission denied" or a save that fails: you opened the file without sudo. Exit and use the sudo nano command above.
• Your edit seems ignored: flush the cache, then try the site in a private window. Look for a typo, such as a missing space between address and name.
• Wildcards do not work: the hosts file matches exact names only. *.example.com has no effect, so list each subdomain, including www. if the site uses it.
• Ports: the file maps names, not ports. 127.0.0.1 myapp.test still needs the port in the URL.
• Pasted lines: curly quotes or non-breaking spaces copied from a web page can break a line. Type the line yourself.

Undo your changes

To go back to your backup:

sudo cp ~/hosts.backup /etc/hosts

That overwrites the current file, so run it only when you mean to, then flush the cache. With no backup, remove your own lines with sudo nano /etc/hosts until only the comment header and the three stock lines above remain.

When to use it

The hosts file suits a handful of fixed entries: pointing a development domain at your own Mac, testing a site on a new server before DNS changes, or blocking a few known domains. For many entries, or for blocking across a whole network, a DNS-level or router setting is easier to maintain than a long hand-edited file.

Backups and a new Mac

The file belongs to the Mac, not to your user account. After moving to a new Mac or reinstalling macOS, check /etc/hosts and add back any lines you rely on. Keeping them in a note, or in the hosts.backup copy in your home folder, makes that a two-minute job.

Why a normal search misses it

/etc is a hidden system folder, and the file has no extension. Finder searches skip it, and Spotlight does not show system files in normal results.

Finding it again

Type hosts into Everywhere to find the file in /private/etc, the real folder behind /etc, next to copies such as hosts.backup. The word hosts also matches plenty of unrelated names, so check the folder column before you choose, then press ⌘T to open a Terminal there. It searches file names only, not the lines inside the file.

Common questions

Where is the hosts file on a Mac?

At /etc/hosts, which is the same file as /private/etc/hosts. Reveal it in Finder with open -R /etc/hosts.

How do I edit /etc/hosts on macOS?

Back it up with cp /etc/hosts ~/hosts.backup, then run sudo nano /etc/hosts, add a line such as 127.0.0.1 example.test, save with ⌃O and exit with ⌃X.

How do I flush DNS on a Mac?

Run sudo dscacheutil -flushcache; sudo killall -HUP mDNSResponder in Terminal. It prints nothing on success.

Why is my hosts file edit not working?

The DNS cache, a browser's own cache, a VPN or browser DNS over HTTPS can all get in the way. Flush the cache, check for typos, and test in a private window.