hyperlink

Very fast link checker for static sites.

• Supports traversing file-system paths only, no arbitrary URLs.

  • No support for the <base> tag.

  • No support for external links. It does not know how to speak HTTP.

• Does not honor robots.txt. A broken link is still broken for users even if not indexed by Google.

• Does not parse CSS files, as broken links in CSS have not been a practical concern for us. We are concerned about broken link in the page content, not the chrome around it.

• Only supports UTF-8 encoded HTML files.

• Fast. docs.sentry.io produces 1.1 GB of HTML files. All alternatives we tried were too slow for this.

  hyperlink handles this amount of data in 4 seconds on a MacBook Pro 2018.

• Pay for what you need. By default, hyperlink checks for hard 404s in internal links only. Anything beyond that is opt-in. See Options for a list of features to enable.

Usage

Install Rust, and:

cargo build --release ./target/release/hyperlink public/

Options

When invoked without options, hyperlink only checks for 404s of internal links. However, it can do more.

• -j/--jobs: How many threads to spawn for parsing HTML. By default hyperlink will attempt to saturate your CPU.

• --check-anchors: Opt-in, check for validity of anchors on pages. Broken anchors are considered warnings, meaning that hyperlink will exit 2 if there are only broken anchors but no hard 404s.

• --sources: A folder of markdown files that were the input for the HTML hyperlink has to check. This is used to provide better error messages that point at the actual file to edit. hyperlink does very simple content-based matching to figure out which markdown files may have been involved in the creation of a HTML file.

  Why not just crawl and validate links in Markdown at this point? Answer:

  • There are countless of proprietary extensions to markdown out there for creating intra-page links that are generally not supported by link checking tools.

  • The structure of your markdown content does not necessarily match the structure of your HTML (i.e. what the user actually sees). With this setup, hyperlink does not have to assume anything about your build pipeline.

• --github-actions: Emit GitHub actions errors. This only has an effect with --sources set.

Exit codes

• exit 1: There have been errors (hard 404s)
• exit 2: There have been only warnings (broken anchors)

Alternatives

• linkcheck has slightly above-average performance, great UX and a good set of features (more than hyperlink). Other than performance it worked really well for our usecase, and hyperlink takes some minor UX decisions from linkchecker here and there.

  We tried linkcheck together with http-server on localhost, although that does not seem to be the bottleneck.

• wummel/linkchecker seems to be the most feature rich out of all, but was a non-starter due to performance. This applies to other countless link checkers we tried that are not mentioned here.

• Legend of Link is a link checker in Rust. hyperlink takes the idea of directly using a html/xml tokenizer from there, but does not share any code with it. We haven't been able to get Legend of Link running at all.

• htmltest is one of the fastest linkcheckers we've tried (after disabling most checks to ensure feature parity with hyperlink), however is still slower than hyperlink in single-threaded mode (-j 1)

License

Licensed under the MIT, see ./LICENSE.