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Wraith — A responsive screenshot comparison tool
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Branch: master

Merge pull request #289 from marciovicente/fix_casper_js

Using not operator instead double equal, to avoid error in casperjs
latest commit 7193717e9e
@ChrisBAshton ChrisBAshton authored

Wraith is a screenshot comparison tool, created by developers at BBC News.

What is it?

Wraith uses either PhantomJS, CasperJS or SlimerJS to create screen-shots of webpages on different environments and then creates a diff of the two images, the affected areas are highlighted in blue

Photo of BBC News with a


The main documentation can be found here, this will cover all the features and options for Wraith as well as sample configs.


Imagemagick and PhantomJS are required to use Wraith, install via your favourite package manager. You can also use SlimerJS and CasperJS, CasperJS can be used to target specific selectors. To read our detailed instructions for setup and install, as well as example configs, visit wraith docs

brew install phantomjs
brew install imagemagick


Open terminal and run

gem install wraith

You can then run the following to create a template snap.js and config file:

wraith setup

Using Wraith

You can type wraith into terminal to bring up the list of commands, but the one to start Wraith is

wraith capture config_name

This assumes that your snap.js and config.yaml are in the folders that were created on setup. To run the setup, create a folder and inside run

wraith setup


There are other commands also available, these all expect a config_name to be passed as an option. Wraith will look for the config file at configs/[config_name].yaml.

  wraith capture [config_name]              # A full Wraith job
  wraith compare_images [config_name]       # compares images to generate diffs
  wraith crop_images [config_name]          # crops images to the same height
  wraith generate_gallery [config_name]     # create page for viewing images
  wraith generate_thumbnails [config_name]  # create thumbnails for gallery
  wraith history [config_name]              # Setup a baseline set of shots
  wraith latest [config_name]               # Capture new shots to compare with baseline
  wraith multi_capture [filelist]           # A Batch of Wraith Jobs
  wraith reset_shots [config_name]          # removes all the files in the shots folder
  wraith save_images [config_name]          # captures screenshots
  wraith setup                              # creates config folder and default config
  wraith setup_casper                       # creates config folder and default config for casper
  wraith setup_folders [config_name]        # create folders for images


After each screenshot is captured, the compare task will run, this will output a diff.png and a data.txt. The data.txt for each file will show the number of pixels that have changed. There is a main data.txt which is in the root of the output folder that will combine all of these values to easier view all the pixel changes.


A gallery is available to view each of the images and the respective diff images located in the shots folder once all the images have been compared. You can set thresholds in the config file, if above this value, the gallery will indicate the shots above the threshold.

Changelog - updated 2014-12-09

In the latest release I have implemented thresholds for Wraith, this makes finding failed shots easier. Set the threshold value in the config to a value you want, by default it is 0. When a failure is detected, the terminal will show a failure message and the gallery will have a red cross next to the set of shots.


If you want to add functionality to this project, pull requests are welcome.

  • Create a branch based off master and do all of your changes with in it.
  • If you have to pause to add a 'and' anywhere in the title, it should be two pull requests.
  • Make commits of logical units and describe them properly
  • Check for unnecessary whitespace with git diff --check before committing.
  • If possible, submit tests to your patch / new feature so it can be tested easily.
  • Assure nothing is broken by running all the test
  • Please ensure that it complies with coding standards.

Please raise any issues with this project as a GitHub issue.


Wraith is available to everyone under the terms of the Apache 2.0 open source license. Take a look at the LICENSE file in the code.



Anyone interested in integrating selenium capability with Wraith should check out Selenium-Wraith by Andrew Tekle-Cadman of Future Visible.

Selenium-Wraith was forked from the BBC repo on 16/04/14 and adds the following capabilities to Wraith

  1. Selenium integration, both running locally on a desktop or on a selenium grid
  2. Browser to browser screenshot comparison
  3. Page component-based comparison

You can check out Andrew's Project on GitHub here:

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