Check the links you send people to

How to do it

Read the links from the built site or its machine-readable index, not from a hand-kept list. Drop the # part and fetch each address once, a few at a time. Send a user agent that names the check. Some sites answer HEAD with an error, so use GET and cancel the body. Retry once before you count a failure, because many failures last only a minute. Replace a dead link with the new address of the same text, or remove it. Run the check outside the deploy, because another site's outage must never block a release.

Examples

Using these examples: they show one way to follow this rule. Keep the behaviour and the check, not the syntax. Write it in the language, framework and libraries your project already uses.

JavaScript example

async function isLinkAlive(url, attempts = 2) {
  for (let attempt = 1; attempt <= attempts; attempt++) {
    const res = await fetch(url, { headers: { 'user-agent': 'example-link-check' }, signal: AbortSignal.timeout(20_000) }).catch(() => null);
    await res?.body?.cancel();
    if (res?.ok) return true;
  }
  return false;
}

Python example

import urllib.request

def is_link_alive(url: str, attempts: int = 2) -> bool:
    request = urllib.request.Request(url, headers={"User-Agent": "example-link-check"})
    for _ in range(attempts):
        try:
            with urllib.request.urlopen(request, timeout=20) as response:
                return 200 <= response.status < 300
        except Exception:
            continue
    return False

How to check

Point one link at an address that answers 404. The next run alerts with that address.

Related rules

• Watch cited sources in code in Engineering
• Link only to final addresses in Website