SXG Checker

A library and command-line tool for checking the Google Signed Exchanges (SXG) cache for the presence of a document and its subresources.

It verifies if your web page and its resources are properly available in Google's SXG cache, helping you troubleshoot SXG implementation issues with detailed status reporting for each resource.

SXG enables websites to optimize Largest Contentful Paint (LCP) by allowing prefetching directly from the Google search results page. For a step-by-step guide, see my SXG tutorial.

Status indicators

Symbol	Status	Description
✓	ok	Resource exists and is valid
?	missing	Resource not found in SXG cache
x	invalid	Resource exists but its signature is invalid
!	parsing_error	Unable to parse the SXG resource
~	links_mismatch	The subresources specified in SXG don't match subresources to be prefetched from SXG cache
≠	integrity_mismatch	Subresource integrity hash mismatch

Installation

Make sure to install dump-signedexchange.

If you intend to use it as a library for your app, add to your Gemfile:

gem "sxg_checker"

Otherwise, to make the command-line tool available to all users in the system, run:

sudo gem install sxg_checker

If you prefer to make it available to yourself only, execute instead:

gem install --user-install sxg_checker

In case of user-specific installation, make sure to add the directory containing the executable to your $PATH. You can find the executable location by running:

gem contents sxg_checker | grep sxg-checker

Usage

Command line

To check a URL in Google's SXG cache:

sxg-checker validate https://www.yourwebsite.com/your-page

To get full usage instructions, run:

sxg-checker --help

In Ruby applications

You can also use SXG Checker as a library in your Ruby applications:

require 'sxg_checker'

checker = SxgChecker::Checker.new(tool: '/usr/local/bin/dump-signedexchange') # The `tool` parameter is optional
document = checker.validate(url)

# Access the results
puts document.url    # The URL of the cached document
puts document.status # The status symbol (:ok, :missing, etc.)

# Iterate through subresources
document.subresources.each do |subresource|
  puts "#{subresource.url}: #{subresource.status}"
end

# If you want to skip validating subresources
result = checker.validate(url, subresources: false)

# If you want to only warm the SXG cache for a given URL
checker.warm_cache(url)

Development

After checking out the repo, run bundle install to install dependencies. Then, run bundle exec rake spec to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To build the gem, run bundle exec rake build. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and the created tag, and push the .gem file to rubygems.org.

Contributing

Bug reports and pull requests are welcome on GitHub at [https://github.com/pepawel/sxg_checker]. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the code of conduct.

Author

My name is Paweł Pokrywka and I'm the author of SXG Checker.

If you want to contact me or get to know me better, check out my blog.

License

The software is available as open source under the terms of the MIT License.

sxg_checker

Runtime