How to fix W: Failed to fetch URL Connection timed out in APT

First, verify that your system has basic network connectivity:

# Test connectivity to a public DNS
ping -c 3 8.8.8.8

# Test connectivity to a major site
ping -c 3 google.com

# Test HTTPS connectivity to a repository
curl -v https://archive.ubuntu.com/ubuntu/dists/jammy/Release

If these basic tests fail, the issue is with your network connection rather than APT specifically.

Corrupted or partial cache files can cause fetch failures. Start with the gentle, non-destructive cleanup and re-run the update:

# Remove cached .deb files (safe, packages re-download as needed)
sudo apt clean

# Refresh package lists
sudo apt update

If apt update still fails after apt clean, escalate to clearing the downloaded package lists so APT re-fetches all metadata from scratch:

# Remove cached package lists (forces a full metadata refresh)
sudo rm -rf /var/lib/apt/lists/*
sudo mkdir -p /var/lib/apt/lists/partial

sudo apt update

Delete the lists directory only as a second step; apt clean alone resolves most cache-related fetch problems.

The default mirror may be slow or geographically distant. Select a mirror closer to your location:

# Edit sources.list
sudo nano /etc/apt/sources.list

Replace the mirror domain with a faster alternative. For example, if using Ubuntu:

- Change archive.ubuntu.com to your country code mirror: us.archive.ubuntu.com, eu.archive.ubuntu.com, etc.
- Or try a mirror from your ISP or local mirror service

For Debian, check https://www.debian.org/mirror/list for nearby mirrors.

Save and try updating:

sudo apt update

If you're unsure which mirror to choose, test connectivity first:

# Test a specific mirror
curl -I https://us.archive.ubuntu.com/ubuntu/

Configure APT to wait longer before timing out connections:

# Create a timeout configuration
sudo nano /etc/apt/apt.conf.d/99timeout

Add these lines to increase timeout values:

Acquire::http::Timeout "300";
Acquire::https::Timeout "300";
Acquire::ftp::Timeout "300";
Acquire::Retries "3";

These settings give APT 5 minutes (300 seconds) to establish connections and retry up to 3 times. Save and test:

sudo apt update

Adjust the timeout value (in seconds) based on your network speed. For slow connections, 600 seconds (10 minutes) may be appropriate.

Slow or unreliable DNS can cause timeout errors. On modern Ubuntu and Debian systems, /etc/resolv.conf is usually a managed symlink (to systemd-resolved or NetworkManager) that gets regenerated on the next reboot or network change. Editing it directly is non-persistent, so configure DNS through the resolver service first.

Persistent fix (systemd-resolved):

# Edit the systemd-resolved configuration
sudo nano /etc/systemd/resolved.conf

Under the [Resolve] section, set:

DNS=8.8.8.8 8.8.4.4 1.1.1.1 1.0.0.1
FallbackDNS=9.9.9.9

Restart the service so the change takes effect, then test:

sudo systemctl restart systemd-resolved
sudo apt update

Verify the active resolvers with resolvectl status.

If your system manages DNS through NetworkManager, set the DNS on the active connection instead so it survives reboots:

sudo nmcli connection modify "<connection-name>" ipv4.dns "8.8.8.8 1.1.1.1"
sudo nmcli connection modify "<connection-name>" ipv4.ignore-auto-dns yes
sudo nmcli connection up "<connection-name>"

Temporary test only (non-persistent): On a system without a DNS manager (or just to confirm DNS is the culprit before applying a persistent fix), you can edit /etc/resolv.conf directly. Be aware this is overwritten on the next reboot or network change:

sudo nano /etc/resolv.conf

nameserver 8.8.8.8
nameserver 1.1.1.1

If this resolves the timeouts, apply the persistent method above to make it stick.

In some environments, IPv6 connectivity is broken or slower than IPv4. Force APT to use only IPv4:

# One-time IPv4-only update
sudo apt -o Acquire::ForceIPv4=true update

To make this permanent:

# Create APT configuration
sudo nano /etc/apt/apt.conf.d/99force-ipv4

Add:

Acquire::ForceIPv4 "true";

Save and test:

sudo apt update

If you're behind a corporate firewall or proxy, ensure APT can connect:

# Test connection to repository directly
curl -v http://archive.ubuntu.com/ubuntu/dists/jammy/Release

If connections are blocked, configure your proxy:

# Create proxy configuration
sudo nano /etc/apt/apt.conf.d/99proxy

Add your proxy settings:

Acquire::http::Proxy "http://proxy.example.com:8080";
Acquire::https::Proxy "http://proxy.example.com:8080";

Then test:

sudo apt update

For authenticated proxies, embedding credentials in the URL writes them in plaintext to a world-readable config file. Prefer to keep credentials out of the URL where possible; if you must use them, restrict permissions on the file (sudo chmod 600 /etc/apt/apt.conf.d/99proxy):

Acquire::http::Proxy "http://username:password@proxy.example.com:8080";

Check that your sources.list contains valid repository URLs that haven't been deprecated:

# View current sources
cat /etc/apt/sources.list
ls -la /etc/apt/sources.list.d/

Look for:
- Outdated domain names (e.g., old Ubuntu release mirrors)
- Typos in URLs
- Repositories that no longer exist

For Ubuntu LTS releases that have reached end-of-life, archive mirrors may be required:

# For end-of-life Ubuntu releases
sudo sed -i 's/archive.ubuntu.com/old-releases.ubuntu.com/g' /etc/apt/sources.list
sudo sed -i 's/security.ubuntu.com/old-releases.ubuntu.com/g' /etc/apt/sources.list

sudo apt update

For currently supported releases, verify you're using the correct mirror URLs from the official Ubuntu or Debian mirror lists.

Enable verbose logging to see exactly where the timeout is occurring:

# Run apt update with debug output
sudo apt update -V

# Or with even more verbose output
sudo apt -o Debug::Acquire::http=true update

The verbose output shows:
- Which specific URLs are timing out
- How long each connection attempt takes
- Which mirrors succeed and which fail

This helps identify if the issue is with a specific mirror or all mirrors. If only one mirror times out while others work, consider removing that mirror from your sources.list.