You open the hosts file, change one line, hit save, and get Permission denied.
That is normal. The system hosts file is protected on purpose.
Why it happens
On macOS and Linux, /etc/hosts is owned by root.
On Windows, C:\Windows\System32\drivers\etc\hosts needs Administrator rights.
A normal editor process cannot overwrite it.
macOS / Linux fix
Edit with elevated rights:
sudo nano /etc/hosts
Or open your editor as root:
sudo code /etc/hosts
# or
sudo vim /etc/hosts
Safer pattern: edit a copy you own, then install it:
cp /etc/hosts ~/hosts.work
# edit ~/hosts.work
sudo cp /etc/hosts "/etc/hosts.bak.$(date +%Y%m%d-%H%M%S)"
sudo cp ~/hosts.work /etc/hosts
Then flush DNS.
Windows fix
- Start Notepad as Administrator
- File → Open
- Go to
C:\Windows\System32\drivers\etc\
- Set the filter to All Files
- Open
hosts
- Save
If Notepad was not elevated, Windows often lets you open the file and then fails on save.
PowerShell alternative:
Start-Process notepad C:\Windows\System32\drivers\etc\hosts -Verb RunAs
Then:
ipconfig /flushdns
"I can edit but nothing changes"
That is a different bug:
- you saved a copy in Downloads / Desktop
- the line is still commented with
#
- DNS cache was not flushed
- another line for the same hostname wins
Verify the live file:
grep -n "myapp.test" /etc/hosts
Avoid fighting permissions every day
Keep project hosts snippets in your repo or home folder. Copy them into place with one sudo command when needed.
That keeps the protected system file boring, and your editable copy easy to version.
Quick recovery if you break hosts
You should still be able to reach the machine by IP and local loopback. Restore from your backup:
sudo cp /etc/hosts.bak.YYYYMMDD-HHMMSS /etc/hosts
If you did not make a backup, most OS installs still have a minimal localhost block you can recreate. Do that before you go hunting for network bugs.
If you switch hosts a lot, a small desktop manager helps keep profiles and DNS flush in one place: Locahl.