If your site serves multiple languages, hreflang is where SEO quietly breaks: page A links B, B never links back; someone writes en_US instead of en-US; an alternate points at a redirect; the target canonicalizes somewhere else. None of it is visible in the browser — all of it costs you in the SERPs.
hreflang-audit is a single-file Node.js 20+ CLI with zero npm dependencies. It crawls your site (or parses your XML sitemap, sitemap-index included), reads <link rel="alternate" hreflang> elements, HTTP Link: headers, and xhtml:link sitemap entries, and runs 11 checks — from invalid ISO codes (with hints like en-UK → en-GB) to missing return links and canonical conflicts.
Every finding comes with a fix hint. Output is a human-readable report, or --json for machines, with exit codes designed for CI. There's also a composite GitHub Action so you can run it on a weekly schedule and fail the build when hreflang regresses.
Try it in under a minute (no npm install)
git clone https://github.com/madahzadeh/hreflang-audit.git
