postgres:18 vs postgres:18-alpine

The short answer

• postgres:18-alpine is 157 MB smaller unpacked on amd64 (307 MB vs 464 MB, 34% less).
• As a download, postgres:18-alpine is 120 MB compressed against 162 MB for postgres:18: 1.4× less to pull.
• postgres:18-alpine has fewer known vulnerabilities: 86 (28 critical or high) against 378 (88 critical or high) in postgres:18.
• 61 of postgres:18's 378 findings have a fixed version available upstream.
• 86 of postgres:18-alpine's 86 findings have a fixed version available upstream.
• Base OS: postgres:18 is built on Debian 13.7 (trixie); postgres:18-alpine on Alpine Linux 3.24.3.
• Alpine images use musl libc instead of glibc. Most software runs unchanged; prebuilt binaries linked against glibc (some Python wheels, Node native modules, vendor agents) may not.
• Packages detected: 149 in postgres:18, 57 in postgres:18-alpine.
• Filesystem layers: 13 vs 9.
• Platforms: only postgres:18 ships arm/v5; only postgres:18-alpine ships arm/v6.