Jekyll::URLMetadata

A jekyll plugin to extract meta information from urls and expose them to liquid variables.

This gem was originally authored to be used as a custom plugin for the static site of genicsblog.com

Installation

Add this line to your application's Gemfile inside the jekyll_plugins group:

group :jekyll_plugins do
    # other gems
    gem "jekyll-url-metadata"
end

Then, enable the plugin by adding it to the plugins section in the _config.yml file:

plugins:
    # - other plugins
    - jekyll-url-metadata

And then execute:

bundle install

Usage

This plugin is essentially a filter and works on any valid URL string provided inside a liquid tag. Use it as below:

{% assign meta = "https://wikipedia.org" | metadata %}

The metadata filter extracts the meta data from the given url string and returns the data as a Hash.

These are the values that are extracted:

• The <title> tag.
• The <meta> tags that have a name, property or charset fields.
• The <link> tags with a rel attribute.

The expected output for {{ meta }} from the above example would be:

{
  "title" => "Wikipedia",
  "charset" => "utf-8",
  "description" => "Wikipedia is a free online encyclopedia, created and edited by volunteers around the world and hosted by the Wikimedia Foundation.",
  "viewport" => "initial-scale=1,user-scalable=yes",
  "apple-touch-icon" => "/static/apple-touch/wikipedia.png",
  "shortcut icon" => "/static/favicon/wikipedia.ico",
  "license" => "//creativecommons.org/licenses/by-sa/3.0/",
  "preconnect" => "//upload.wikimedia.org"
}

Connection time-outs

By default, the connection request to the specified domain closes after about 1 second if there is an error.

To override the default behavior, add this block to the _config.yml file:

url_metadata:
  open_timeout: 5 # timeout after 5 second if connection doesn't open
  read_timeout: 3 # timeout after 3 second if there's no data returned

Note: You may use any number for the timeout seconds, but generally a number less than 10 is ideal for better performance because the processing of the static pages is blocked until some data is returned from a website.

Caching

Once the initial data is returned from the website, the extracted parameters are stored in the .jekyll-cache folder under Jekyll--URLMetadata plugin cache folder.

The cache improves subsequent build times in the local development environment.

If you wish to purge the cache, simple delete the Jekyll--URLMetadata folder and the plugin will re-generate the cache in the next run.

Use cases

• Creating beautiful social previews for links by fetching meta data for URLs at build time.
• Determining meta data from a website at jekyll build time to evaluate and perform certain action.

License

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