How to fix E: Acquire::http::Proxy URL is invalid in APT

APT proxy settings are stored in configuration files under /etc/apt/apt.conf.d/. Search for any proxy-related configuration:

sudo grep -r "Acquire::.*Proxy" /etc/apt/apt.conf.d/

Also check the main configuration file:

sudo grep -r "Acquire::.*Proxy" /etc/apt/apt.conf

This will show you all lines where proxy settings are defined. Note the file names and line numbers where these appear.

The correct format for a proxy URL in apt configuration is:

scheme://[[user][:pass]@]host[:port]/

Valid examples:

Acquire::http::Proxy "http://proxy.example.com:8080/";
Acquire::https::Proxy "https://proxy.example.com:8443/";
Acquire::http::Proxy "http://username:[email protected]:8080/";
Acquire::http::Proxy "socks5h://127.0.0.1:1080/";

Common mistakes to avoid:
- Missing "http://" or other scheme prefix
- Using "http:/proxy" instead of "http://proxy" (missing one slash)
- Writing "Acquire_http" instead of "Acquire::http"
- Forgetting the trailing slash after the port
- Missing quotes around the URL
- Missing the semicolon at the end

If your proxy password contains special characters like @ # % & = +, they must be URL-encoded:

# Example: password is "p@ss=word#123"
# URL-encode: p%40ss%3Dword%23123

Acquire::http::Proxy "http://username:p%40ss%3Dword%[email protected]:8080/";

Common URL encodings:
- @ becomes %40
- # becomes %23
- % becomes %25
- & becomes %26
- = becomes %3D
- : becomes %3A (only encode in password, not in scheme://)

To safely encode your password, use this command:

echo -n "your-password" | jq -sRr @uri

Open your proxy configuration file with a text editor:

sudo nano /etc/apt/apt.conf.d/70debconf

Or create a new proxy-specific file:

sudo nano /etc/apt/apt.conf.d/proxy.conf

Update the proxy lines with correct formatting. Example valid configuration:

Acquire::http::Proxy "http://192.168.1.100:3128/";
Acquire::https::Proxy "https://192.168.1.100:3128/";
Acquire::ftp::Proxy "ftp://192.168.1.100:3128/";

Make sure each line:
1. Uses correct scheme (http://, https://, socks5h://)
2. Has proper host:port separator
3. Ends with a trailing slash
4. Has quotes around the entire URL
5. Ends with a semicolon

Save the file (Ctrl+O, Enter, Ctrl+X in nano).

After fixing the configuration, test if apt accepts it:

sudo apt update

If you still see "URL is invalid", check the exact error message for which line has the problem:

sudo apt -o Debug::Acquire::http=true update 2>&1 | grep -i proxy

If the error persists, verify syntax by checking what apt loaded:

sudo apt-config dump | grep -i proxy

This shows exactly how apt parsed your configuration. Compare it to your intended proxy URL.

If you cannot get the proxy working, you can temporarily disable it to resume normal apt operations:

sudo nano /etc/apt/apt.conf.d/proxy.conf

Comment out or delete the proxy lines:

# Acquire::http::Proxy "http://proxy:8080/";
# Acquire::https::Proxy "https://proxy:8080/";

Or use the special value DIRECT to disable proxy:

Acquire::http::Proxy "DIRECT";
Acquire::https::Proxy "DIRECT";

Save and test:

sudo apt update