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Check if urls are dead or alive.

• What is this?
• When should I use this?
• Install
• Use
• API
  • deadOrAlive(href[, options])
  • defaultAnchorAllowlist
  • defaultSleep(retries)
  • AnchorAllow
  • Options
  • Result
  • Sleep
• Errors
  • dead
  • fetch
  • lost-hash-with-meta-http-equiv
  • lost-hash-with-non-html
  • lost-hash-with-redirect
  • max-redirect
  • missing-anchor
  • shared-declarative-refresh
• Compatibility
• Security
• Contribute
• License

The main goal of this project is to make sure URLs in docs are okay.As in,“if I link to it and a user goes there,will it work,and will they be there or somewhere else?”It uses modern JavaScript that works everywhere,and it uses the DOM when available,so you can use it in browsers, Node.js, workers.

It is made to be used by other tools.Such as a markdown tool,remark-lint-no-dead-urls.

• works in browser, node, worker, etc
• checks if anchors (such as#readme) point to elements
• follows HTTP and HTML redirects
• supports DOM clobber prefix (user-content-)
• emits warnings

You can use this when you want to build a link checker.

If you want to support SPAs or other client-side JS,this doesn’t do that.

This package isESM only.In Node.js (version 18+),install withnpm:

npm install dead-or-alive

In Deno withesm.sh:

import{deadOrAlive}from'https://esm.sh/dead-or-alive@1'

In browsers withesm.sh:

<scripttype="module">import{deadOrAlive}from'https://esm.sh/dead-or-alive@1?bundle'</script>

import{deadOrAlive}from'dead-or-alive'console.log(awaitdeadOrAlive('https://something-that-is-dead.com'))console.log(awaitdeadOrAlive('https://github.com'))

…yields:

{  messages: [    [1:1: Unexpected error fetching `https://something-that-is-dead.com/`] { … }  ],  status: 'dead',  url: undefined,  urls: undefined}{  messages: [],  status: 'alive',  url: 'https://github.com/',  urls: Set(203) {    'https://github.githubassets.com/',    'https://avatars.githubusercontent.com/',    …  }}

This package exports the identifiersdeadOrAlive,defaultAnchorAllowlist,anddefaultSleep.It exports the TypeScript typesAnchorAllow,Options,Result,andSleep.There is no default export.

Check if a url is dead or alive.

• href (URL orstring)— URL
• options (Options, optional)— configuration

Result (Promise<Result>).

To improve performance,decreasemaxRetries and/or decrease the value usedforsleep.The normal behavior is to assume connections might be flakey and to sleep awhile and retry a couple times.

If you do not care about HTML redirects,whether anchors work,and what further URLs are used on,you can passcheckAnchor: false,findUrls: false,andfollowMetaHttpEquiv: false,which enables a fast path without parsing HTML.

Allow certain anchors (Array<AnchorAllow>).

This currently allows text fragments everywhere.

Calculate milliseconds to sleep between tries.

The function is defined asx ** 3 * 1000,so the first sleep is1 ** 3 * 1000 is 1s,2nd is 8s,3rd is 27s,etc.

• retries (number)— try

Milliseconds to sleep (number).

Allow extra anchors (TypeScript type).

The first item is a regular expression to match URLs (origin and path,so without search or hash),and the second item is a regular expression to match hashes (without#).When both match,the hash is allowed.

exporttypeAnchorAllow=[url:RegExp,anchor:RegExp]

Configuration (TypeScript type).

• anchorAllowlist (Array<AnchorAllow>, default:true)— allow anchors;each tuple is checked to match URLs (origin and path,so without search or hash),and then to match hashes (without#);when both match,the hash is allowed,and nomissing-anchor error is used
• checkAnchor (boolean, default:true)— check whether URL hashes point to elements
• followMetaHttpEquiv (boolean, default:true)— follow HTML redirects;a<meta content=0;to http-equiv=refresh> can be useful for static sitessuch as those on GH pages
• findUrls (boolean, default:true)— find URLs in the final resource;currently applies to HTML
• maxRedirects (number, default:5)— inclusive maximum redirects to follow
• maxRetries (number, default:1)— inclusive maximum number to try again on failures
• resolveClobberPrefix (boolean, default:true)— acceptuser-content- prefix inid on elements
• sleep (Sleep, default:defaultSleep)— calculate milliseconds to sleep between tries
• timeout (number, default:3000)— timeout for HTTP request in milliseconds
• userAgent (string, default:'Mozilla/5.0 … Safari/537.36',a modern Chrome on macOS user agent)— user agent

Result (TypeScript type).

• messages (Array<VFileMessage>)— messages where the first is a fatal error when dead
• permanent (boolean orundefined)— whether all redirects were permanent
• status ('alive' or'dead')— status
• url (string orundefined)— final URL if alive
• urls (Set<string> orundefined)— further URLs iffindUrls: true and the resource was HTML

Calculate milliseconds to sleep between tries (TypeScript type).

• retries (number)— try

Milliseconds to sleep (number).

Unexpected not ok response `$status` (`$statusText`) on `$url`

This error is used when a URL looks temporarily or permenantly dead.

Unexpected error fetching `$url`

This error is used when for some unknown reason the URL is dead.It might be that you are offline,or the URL is temporarily dead,or something else is wrong.But it looks dead.

Unexpected hash in URL `$url` thatredirects with `meta[http-equiv=refresh]` to `$url` losing the hash, remove the hash from the original URL

This warning is used when a URL with an anchor gets an HTML redirect,which looses that anchor.You can remove the hash from the original URL.Or find a similar section on the final URL.

Unexpected hash in URL `$url` to non-html ($contentType) losing the hash, remove the hash from the original URL

This warning is used when a URL with an anchor resolves to some non-HTML thing,which might be an error.Perhaps you can remove the hash from the original URL?

Unexpected hash in URL `$url` thatredirects to `$url` losing the hash, remove the hash from the original URL

This warning is used when a URL with an anchor gets an HTTP redirect,which looses that anchor.You can remove the hash from the original URL.Or find a similar section on the final URL.

Unexpected redirect to `$url`, too manyredirects

This error is used when there are more redirects thanoptions.maxRedirects.Increase this number or use your browser to see if the URL ends up redirectingto something that works.

Unexpected missing anchor element on `$url` for fragment `$fragment`, remove if unneeded or refer to an existing element

This error is used when a hash is used in a URL but no such element can befound.Elements can match hashes by theirid or by theirname (when<a>).The prefixuser-content- is ignored on elements as that’s what GitHub andrehype-sanitize use to solve DOM clobbering.

Remove the hash if unneeded or refer to a different,existing element.

Unexpected invalid URL `$url` in `content` on `meta[http-equiv=refresh] relative to `$url`

This error is used when an HTML redirect such as<meta content=0;xxx http-equiv=refresh> is used,butxxx does not parse as a URL.Use your browser to see if the URL ends up redirecting to something that works.

This projects is compatible with maintained versions of Node.js.

When we cut a new major release,we drop support for unmaintained versions of Node.This means we try to keep the current release line,dead-or-alive@1,compatible with Node.js 18.

This package is safe.

Yes please!SeeHow to Contribute to Open Source.

MIT ©Titus Wormer