Changing APT Mirrors

Switch Debian 13 to a faster APT mirror: deb822 .sources and the classic sources.list formats, a comparison of popular mirrors, the security line, and common errors.

Access to deb.debian.org can be slow depending on where you are; switching APT to a nearby mirror makes apt update an order of magnitude faster. Debian 13 uses the deb822 format (the installer writes /etc/apt/sources.list.d/debian.sources by default); the classic one-line-per-repo format (/etc/apt/sources.list) keeps working too. Pick one — don't mix both.

Popular mirrors

Mirror	URL
Debian official	`https://deb.debian.org/debian/`
MIT (US)	`https://mirrors.mit.edu/debian/`
Kernel.org (US)	`https://mirrors.kernel.org/debian/`
University of Waikato (NZ)	`https://debian.netcology.nz/debian/`

Not sure which? Our mirror picker generates the configuration for your location automatically.

Don't forget the security line

A common mistake is switching the main repo while trixie-security still points at the official source. Replace the security line in the examples below together with the main repo.

Option 1: deb822 format (Debian 13 default)

Edit /etc/apt/sources.list.d/debian.sources (using the official source, MIT as an example):

Types: deb
URIs: https://mirrors.mit.edu/debian/
Suites: trixie trixie-updates trixie-security
Components: main contrib non-free non-free-firmware
Signed-By: /usr/share/keyrings/debian-archive-keyring.gpg

Suites should include trixie, trixie-updates, and trixie-security. Security updates ship from the debian-security suite; keep an eye on whether your mirror also carries it (major mirrors do, under the same domain).

Option 2: classic sources.list format

Edit /etc/apt/sources.list:

deb https://deb.debian.org/debian/ trixie main contrib non-free non-free-firmware
deb https://deb.debian.org/debian/ trixie-updates main contrib non-free non-free-firmware
deb https://deb.debian.org/debian-security trixie-security main contrib non-free non-free-firmware

Note the security line lives under debian-security, not /debian/ trixie-security. If both /etc/apt/sources.list and /etc/apt/sources.list.d/debian.sources exist, rename the unused one (e.g. add a .bak suffix) — otherwise the same packages get defined twice.

Apply and verify

sudo apt update
apt policy firefox-esr | head -5

A clean apt update plus candidate versions pointing at the mirror means the switch worked. 404s during upgrade usually mean a typo in the suites or a mirror that hasn't finished syncing.

Common issues

Issue	Cause and fix
`404 Not Found`	Mirror still syncing, or wrong suite (trixie, not bookworm)
GPG signature errors	Wrong `Signed-By` path; Debian 13's keyring is `/usr/share/keyrings/debian-archive-keyring.gpg`
Slower after switching	DNS-related; prefer a direct HTTPS mirror over HTTP proxies
Need non-free software	Keep `contrib non-free non-free-firmware` in `Components`

Next steps

Mirror picker: generate either format for your location automatically
Package management: advanced apt and dpkg usage
Configuration: system settings after the initial setup