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SiteDiff CLI

Warning: SiteDiff 1.2.0 requires at least Ruby 3.1.2.

Warning: SiteDiff 1.0.0 introduces some backwards incompatible changes.

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SiteDiff makes it easy to see how a website changes. It can compare two similar sites or it can show how a single site changed over time. It helps identify undesirable changes to the site's HTML and it's a useful tool for conducting QA on re-deployments, site upgrades, and more!

When you run SiteDiff, it produces an HTML report showing whether pages on your site have changed or not. For pages that have changed, you can see a colorized diff exactly what changed, or compare the visual differences side-by-side in a browser.

SiteDiff supports a range of normalization / sanitization rules. These allow you to eliminate spurious differences, narrowing down differences to the ones that materially affect the site.


SiteDiff is fairly easy to install. Please refer to the installation docs.


After installing all dependencies including the bundle version 2 gem, you can quickly see what SiteDiff can do. Simply use the following commands:

git clone
cd sitediff
bundle install
bundle exec thor fixture:serve

Then visit http://localhost:13080/ to view the report.

SiteDiff shows you an overview of all the pages and clearly indicates which pages have changed and not changed. page report preview

When you click on a changed page, you see a colorized diff of the page's markup showing exactly what changed on the page. page report preview


Here are some instructions on getting started with SiteDiff. To see a list of commands that SiteDiff offers, you can run:

sitediff help

To get help for a particular command, say, diff, you can run:

sitediff help diff

Getting started

To use SiteDiff on your site, create a configuration for your site:

sitediff init

SiteDiff will generate a configuration file named sitediff.yaml by default.

You can open the configuration file sitediff/sitediff.yaml to see the default configuration generated by SiteDiff. The the configuration reference section explains the contents of this file and helps you customize it as per your requirements.

Then get SiteDiff to crawl your site by using:

sitediff crawl

SiteDiff will then crawl your site, finding pages and caching their contents. A list of discovered paths will be saved to a paths.txt file.

Now, you can make alterations to your site. For example, change a word on your site's front page. After you're done, you can check what actually changed:

sitediff diff

For each page, SiteDiff will report whether it did or did not change. For pages that changed, it will display a diff. You can also see an HTML version of the report using the following command:

sitediff serve

SiteDiff will start an internal web server and open a report page on your browser. For each page, you can see the diff and a side-by-side view of the old and new versions.

You can now see if the changes were as you expected, or if some things didn't quite work out as you hoped. If you noticed unexpected changes, congratulations: SiteDiff just helped you find an issue you would have otherwise missed!

As you fix any issues, you can continue to alter your site and run sitediff diff to check the changes against the old version. Once you're satisfied with the state of your site, you can inform SiteDiff that it should re-cache your site:

sitediff store

This takes a snapshot of your website and the next time you run sitediff diff, it will use this new version as the reference for comparison.

Happy diffing!

Comparing 2 sites

Sometimes you have two sites that you want to compare, for example a production site hosted on a public server and a development site hosted on your computer. SiteDiff can handle this situation, too! Just inform SiteDiff that there are two sites to compare:

sitediff init http://localhost/mysite

Then when you run sitediff diff, it will compare the cached version of the first site with the current version of the second site.

If both the first and second sites may be changing, you should tell SiteDiff not to cache either site:

sitediff diff --cached=none

Spurious diffs

Sometimes sites have spurious differences, that you don't want to show up in a comparison. For example, many sites protect against Cross-Site Request Forgery using a semi-random token. Since this token changes on each HTTP GET, you probably don't care about such a change.

To help with issues such as this, SiteDiff allows you to normalize the HTML it fetches as it compares pages. In the sitediff.yaml configuration file, you can add "sanitization rules", which specify either DOM transformations or regular expression substitutions.

Here's an example of a rule you might add to remove CSRF-protection tokens generated by Django:

  - title: Remove CSRF tokens
    type: remove
    selector: input[name=csrfmiddlewaretoken]

You can use one of the presets to apply framework-specific sanitization. Currently, SiteDiff only comes with Drupal-specific presets.

See the preset section for more details.

Command Line Options

Finding configuration files

By default SiteDiff will put everything in the sitediff folder. You can use the --directory flag to specify a different directory.

sitediff init -C my_project_folder
sitediff diff -C my_project_folder
sitediff serve -C my_project_folder

Specifying paths

When you run sitediff diff, you can specify which pages to look at in 2 ways:

  1. The option --paths /foo /bar ....

    If you're trying to fix one page in particular, specifying just that one path will make sitediff diff run quickly!

  2. The option --paths-file FILE with a newline-delimited text file.

This is particularly useful when you're trying to eliminate all diffs. SiteDiff creates a file output/failures.txt containing all paths which had differences, so as you try to fix differences, you can run:

sitediff diff --paths-file sitediff/failures.txt

Debugging rules

When a sanitization rule isn't working quite right for you, you might run sitediff diff many times over. If fetching all the pages is taking too long, try adding the option --cached=all. This tells SiteDiff not to re-fetch the content, but just compare previously cached versions — it's a lot faster!

Including and Excluding URLs

By default sitediff crawls pages that are indicated with an HTML anchor using the <A HREF syntax. Most pages linked will be HTML pages, but some links will contain binaries such as PDF documents and images.

Using the option --exclude='.*\.pdf' ensures the crawler skips links for document with a .pdf extension. Note that the regular expression is applied to the path of the URL, not the base of the URL.

For example --include='.*\.com' will not match, because the path of that URL is / while the base is

paths / paths-file

SiteDiff allows you to specify a list of paths that you want it to work with. Alternatively, it can crawl the entire site and detect all paths.

  • Running sitediff init configures SiteDiff for crawling and seeing differences.

  • Running sitediff crawl makes sitediff crawl your site and detect available paths. These paths are written to a paths.txt file which you can modify according to your needs.

  • You can also compute diffs only for paths specified in a custom paths file using the --paths-file parameter. This file should contain paths starting with a /, having one path per line.

    sitediff diff --paths-file=/path/to/paths.txt
  • You can also compute diffs for a handful of specific paths by specifying them directly on the command line using the --paths parameter. Each path should be separated by a space.

    sitediff diff --paths=/home /about /contact


Generate a gzipped tar file containing the HTML report instead of generating and serving live web pages, this option overrides --report-format, forcing HTML.

sitediff diff --export
sitediff diff -e

This will perform the diff and export the results in a gzipped tar file.

Running inside containers

If you run SiteDiff inside a container or virtual machine, the URLs in its report might not work from your host, such as localhost. You can fix this by using the --before-url-report and --after-url-report options, to tell SiteDiff to use a different URL in the report than the one it uses for fetching.

For example, if you ran sitediff init http://localhost inside a Vagrant VM, you might then run something like:

sitediff diff --after-url-report=http://vagrant:8080


SiteDiff relies on a YAML configuration file, usually called sitediff.yaml. You can create a reasonable one using sitediff init, but there are many useful things you may want to add or change manually.

In the sitediff.yaml, SiteDiff recognizes the keys described below. The config directory contains some example sitediff.yaml files. For example, sitediff.example.yaml.

before_url / after_url

after_url: http://localhost:8080/subsite

They can also be paths to directories on the local filesystem.

The after_url MUST provided either at the command-line or in the sitediff.yaml. If the before_url is provided, SiteDiff will compare the two sites. Otherwise, it will compare the current version of the after site with the stored version of that site, as created by sitediff init or sitediff store.


Chooses the sections of HTML we wish to compare, if you don't want to compare the entire page. For example if you only want to compare breadcrumbs between your two sites, you might specify:

selector: '#breadcrumb'


A list of regular expression rules to normalize your HTML for comparison.

Each rule should have a pattern regex, which is used to search the HTML. Each found instance is replaced with the provided substitute or deleted if no substitute is provided. A rule may also have a selector, which constrains it to operate only on HTML fragments which match that CSS selector.

For example, forms on Drupal sites have a randomly generated form_build_id on form pages:

<input type="hidden" name="form_build_id" value="form-1cac6b5b6141a72b2382928249605fb1"/>

We're not interested in comparing random content, so we could use the following rule to fix this:

# Remove form build IDs
  - pattern: '<input type="hidden" name="form_build_id" value="form-[a-zA-Z0-9_-]+" *\/?>'
    selector: 'input'
    substitute: '<input type="hidden" name="form_build_id" value="__form_build_id__">'

Sanitization rules may also have a path attribute, whose value is a regular expression. If present, the rule will only apply to matching paths.


Ignore whitespace when doing the diff. This passes the -w option to the native OS diff command.

ignore_whitespace: true

On the command line, use -w or --ignore-whitespace.

sitediff diff -w

before / after

Applies rules to just one side of the comparison.

These blocks can contain any of the following sections: selector, sanitization, dom_transform. Such a section placed in before will be applied just to the before side of the comparison and similarly for after.

For example, if you wanted to let different date formatting not create diff failures, you might use the following:

    - pattern: '[1-2][0-9]{3}/[0-1][0-9]/[0-9]{2}'
      substitute: '__date__'
    - pattern:  '[A-Z][a-z]{2} [0-9]{1,2}(st|nd|rd|th) [1-2][0-9]{3}'
      substitute: '__date__'

The above rule will replace dates of the form 2004/12/05 in before and dates of the form May 12th 2004 in after with __date__.


The names of other configuration YAML files to merge with this one.

  - config/sanitize_domains.yaml
  - config/strip_css_js.yaml


A list of transformations to apply to the HTML before comparing.

This is similar to sanitization, but it applies transformations to the structure of the HTML, instead of to the text. Each transformation has a type, and potentially other attributes. The following types are available:


Given a selector, removes all elements that match it.

For example, say we have a block containing the current time, which is expected to change. To ignore that, we might choose to delete the block before comparison:

# Remove current time block
  - type: remove
    selector: div#block-time


Strip leading and trailing whitespace from the contents of a tag.

Uses the Ruby string strip() method. Whitespace is defined as any of the following characters: null, horizontal tab, line feed, vertical tab, form feed, carriage return, space.

To transform <h1> Foo and Bar\n </h1> to <h1>Foo and Bar<\h1>:

# Strip H1 tags
  - type: strip
    selector: h1


Given a selector, replaces all matching elements with their children. For example, your content on one side of the comparison might look like this:

<p>This is some text</p>
<img src="lola.png" alt="Lola is a cute kitten." />

But on the other side, it might be wrapped in an article tag:

  <p>This is some text</p>
  <img src="test.png"/>

You could fix it with the following configuration:

  - type: unwrap
    selector: article


Given a selector and a class, removes that class from each element that matches the selector. It can also take a list of classes, instead of just one.

For example, here are two sample rules for removing a single class and removing multiple classes from all div elements:

  # Remove class foo from div elements
  - type: remove_class
    selector: div
    class: class-foo
  # Remove class bar and class baz from div elements
  - type: remove_class
    selector: div
      - class-bar
      - class-baz


Replaces the entire root element with its children.


The settings under the report key allow you to display helpful details on the report.

  title: "Updates to"
  details: "This report verifies updates to"
  before_note: "The old site"
  after_note: "The new site"


Display a title string at the top of the report.


Text displays as a paragraph at the top of the report, below the title.


Display a brief explanatory note next to before URL.


Display a brief explanatory note next to after URL.

before_url_report / after_url_report

Changes how SiteDiff reports which URLs it is comparing, but don't change what it actually compares.

Suppose you are serving your 'after' website on a virtual machine with IP, and you are also running SiteDiff inside that VM. To make links in the report accessible from outside the VM, you might provide:

after_url: http://localhost

If you don't wish to have the "Before" or "After" links in the report, set to false:

  after_url_report: false



Presets are stored in the /lib/sitediff/presets directory of this gem. You can select a preset as follows:

  preset: drupal

Include/Exclude Paths

exclude paths

A RegEx indicating the paths that should not be crawled.

include paths

A RegEx indicating the paths that should be crawled.

Organizing configuration files

If your configuration file starts getting really big, SiteDiff lets you separate it out into multiple files. Just have one base file that includes other files:

  - sanitization.yaml
  - paths.yaml

This allows you to separate your configuration into logical groups. For example, generic rules for your site could live in a generic.yaml file, while rules pertaining to a particular update you're conducting could live in update-8.2.yaml.

Named regions

In major upgrades and migrations where there are significant changes to the markup, simple diffs will not be of much value. To assist in these cases, named regions let you define regions in the page markup and the specify order in which they should be compared. Specifying the order helps in cases where the fields are not in the same order on the new site.

For example, if you have a CMS displaying title, author, and body fields, you could define the named regions and the selectors for the three fields as follows:

    - name: title
      selector: h1.title
    - name: author
      selector: .field-name-attribution
    - name: body
      selector: .field-name-body

(You need to define regions for both the before and after sections.)

You must then define the order that the fields should be compared, using the output key.

  - title
  - author
  - body

Before the two versions are compared, SiteDiff generates markup with <region> tags and each region contains the markup matching the corresponding selector.


<region id="title">
  <h1 class="title">My Blog Post</h1>
<region id="author">
  <div class="field-name-attribution">
    <span class="label">By:</span> Alfred E. Neuman
<region id="body">
  <div class="field-name-attribution">
    <p>Lorem ipsum...

The regions are processed first, so you can reference the <region> tags to be more specific in your selectors for dom_transform and sanitization sections.


  - name: Remove body div wrapper
    type: unwrap
    selector: region#body .field-name-attribution

Curl Options

Many options can be passed to the underlying curl library. Add --curl_options=name1:value1 name2:value2 to the command line (such as --curl_options=max_recv_speed_large:100000 (remove the CURLOPT_ prefix and write the name in lowercase) or add them to your configuration file.

    max_recv_speed_large: 10000
    ssl_verifypeer: false

These CURL options can be put under the settings section of sitediff.yaml as demonstrated above.


A few options are also available to control how aggressively SiteDiff crawls.

  • There's a command line option --concurrency=N for sitediff init which controls the maximum number of simultaneous connections made. Lower N mean less aggressive. The default is 3. You can specify this in the sitediff.yaml file under the settings key.

  • The underlying curl library has many options such as max_recv_speed_large which can be helpful.

  • There is a special command line option --interval=T for sitediff init. This option and allows the fetcher to delay for T milliseconds between fetching pages. You can specify this in the sitediff.yaml file under the settings key.


By default, no timeout is set but one can be added --curl_options=timeout:60 or in your configuration file.

    timeout: 60 # In seconds; or...
    timeout_ms: 60000 # In milliseconds.

Handling security

Often development or staging sites are protected by HTTP Authentication. SiteDiff allows you to specify a username and password, by using a URL like or by adding a userpwd setting to your file.

SiteDiff ignores untrusted certificates by default. This is equivalent to the following settings:

    ssl_verifypeer: false
    ssl_verifyhost: 0
    userpwd: "username:password"

This contains various parameters which affect the way SiteDiff works. You can have the following keys under settings.


An integer indicating the number of milliseconds SiteDiff should wait for between requests.


The maximum number of simultaneous requests that SiteDiff should make.


The depth to which SiteDiff should crawl the website. Defaults to 3, which means, 3 levels deep.


Options to pass to the underlying curl library. Remove the CURLOPT_ prefix in this full list of options and write in lowercase. Useful for throttling.

    connecttimeout: 3
    followlocation: true
    max_recv_speed_large: 10000

Tips and Tricks

Here are some tips and tricks that we've learned using SiteDiff:

  • Use single quotes or double quotes around selectors. Remember that the # is a comment in YAML.
  • Be specific enough with selectors to not affect elements on other pages.

Removing Empty Elements

If you have an empty <p/> tag appearing in the diff, you can write the following in your sanitization lists:

  - name: remove_empty_p
    pattern: '<p/>'
    substitute: ''

HTML Tag Formatting

There are times when the HTML tags do not have newlines between them on one of the sites you wish to compare. In this case, these sanitzation rules are useful:

  - name: remove_space_before
    pattern: '\s*(\n)<'
    substitute: '\1<'

  - name: remove_space_after
    pattern: '>(\n)\s*'
    substitute: '>\1'

Empty Attributes

After writing rules, you may end up with empty attributes, like width="". Here's a sanitization rule:

  - name: remove_empty_class
    pattern: ' class=""'
    substitute: ''


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