Configure Visual Diffs

Prerequisite: Use Base Previews

In order to configure Tugboat’s visual diffs, you must be using at least one Base Preview. For more info, see: How Visual Diffs work.

How to configure visual diffs

Simple visualdiff configuration

To configure which pages have Visual Diffs generated, specify the relative URLs of the pages in a urls key in the service definition. In this format, each URL can be a string, and you can list multiple urls.

services:
  apache:
    urls:
      # Create visual diffs of the these URLs using the default options
      - /
      - /blog
      - /about

Group visualdiffs via service alias

You can also group URLs by service alias, which is convenient when aliases have different URL structures.

services:
  apache:
    aliases:
      - foo

    urls:
      # Create visualdiffs for the default alias
      :default:
        - /
        - /blog

      # Create visualdiffs for the "foo" alias
      foo:
        - /
        - /about

If you’re not running an apache service on your Preview, but you are running php, set up Visual Diffs under the php service.

Use advanced visualdiff configuration options

You can also use advanced visualdiff configuration options to specify additional criteria for Tugboat to use when generating visual diffs. When you want to specify configuration options beyond the default, you’ll need to use an additional visualdiff key.

You can set visualdiff options for all URLs in the list under the urls key, or under an individual url key to apply the settings to a specific URL. For more information on the configuration options available for visual diffs, see: Tugboat Configuration -> visualdiff and Tugboat Configuration -> urls.

services:
  apache:
    urls:
      # Create a visualdiff of the home page using the default options
      - url: /

      # Create a visualdiff of /blog, but override the default timeout option
      - url: /blog
        visualdiff:
          timeout: 10

      # Create a visualdiff of /about, but override the default waitUntil option
      - url: /about
        visualdiff:
          waitUntil: domcontentloaded

Specify screenshot and visualdiff settings explicitly

Tugboat’s visual diffs depend on an underlying screenshot functionality. Tugboat’s screenshot engine uses Puppeteer to take screenshots of URLs in your Tugboat Preview.

Tugboat’s config.yml gives you the option to specify settings explicitly for both screenshot and visualdiff.

When you specify settings for screenshot, those configuration options determine the screenshots taken of the Preview for which you’re generating visual diffs.

When you specify settings for visualdiff, those configuration options determine the screenshots taken of the Base Preview that Tugboat compares against to generate visual diffs.

For a full list of the configuration options you can use when setting both screenshot and visualdiff options, see: Tugboat Configuration -> screenshot and Tugboat Configuration -> visualdiff.

For example, explicitly setting both of these options in a config.yml might look something like this:

services:
  apache:
    # Screenshot settings that affect all of the defined service URLs.
    # These override our defaults, and can also be overridden per-URL
    screenshot:
      enabled: true

      # The following options are used when taking a screenshot of
      # the URL for _this_ preview
      timeout: 30
      waitUntil:
        - load
      fullPage: true

    # Visual Diff settings that affect all of the defined service URLs.
    # These override our defaults, and can also be overridden per-URL
    visualdiff:
      # Visual Diffs depend on Screenshots being enabled. If Screenshots
      # are disabled for this Service, Visual Diffs are also disabled,
      # and this setting has no effect.
      enabled: true
      # The following options are used when taking a screenshot of
      # the URL for the _base_ preview
      timeout: 30
      waitUntil:
        - load
      fullPage: true

Turn off visual diffs

By default, Tugboat’s URL configuration enables screenshot, visualdiff, and lighthouse functionality. If you only want to view Lighthouse audits for a URL or group of URLs, but want to explicitly turn visual diffs off for one or all pages, you can do that by setting enabled: false. In a config.yml, this might look like:

services:
  apache:
    # Turn off screenshots for all of the defined service URLs.
    # Visual Diffs depend on Screenshots being enabled. If Screenshots
    # are disabled for this Service, Visual Diffs are also disabled.
    # This overrides our defaults, and can also be overridden per-URL
    screenshot:
      enabled: false

    urls:
      # Lighthouse reports will be generated for all URLs. However,
      # with screenshot disabled at the Service level, these pages will
      # not generate visual diffs.
      - /
      - /about
      # Create a visual diff of /blog, overriding the Service-level
      # disabling of screenshots & visual diffs
      - url: /blog
        screenshot:
          enabled: true
        visualdiff:
          enabled: true