Perceptual diffs of responsive screenshots made simple.
Ruby HTML JavaScript CSS
Latest commit 8990f68 May 6, 2016 1 @trotzig trotzig Show warning about project not being maintained
We don't actively work on this project anymore, and we shouldn't let people think it it. Adding a warning at the top of README should help explain this.

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Please note that this project is not actively maintained. Consider using diffux_ci instead.

Build Status Code Climate Coverage Status Dependency Status

Are you worried that your CSS changes will break the current design in unexpected ways? Do you want to show a designer a page you've been working on, before and after your changes? Do you want to be able to quickly look back at how things looked a month or a year ago?

Diffux [dɪˈfjuːz] is a tool that generates and manages visual diffs of web pages, so that you can easily see even the subtlest effects of your code modifications.



Diffux requires:

  • Redis
  • Ruby 2.0.0+
  • ImageMagick (only as part of generating thumbnails, not for creating the diffs)

Optional requirements:

  • PostgreSQL (SQLite is used by default)

Mac OS X (Using Homebrew)

Below are some example installation instructions that might help you get Diffux up and running on Mac OS X using Homebrew.

# clone repo
git clone
cd diffux

# install dependencies
brew update
brew doctor
brew install imagemagick redis

# optionally install and start PostgreSQL (you can leave this step out if you
# are ok with using SQLite)
brew install postgresql
pg_ctl -D /usr/local/var/postgres -l /usr/local/var/postgres/server.log start

# install gems
bundle install

# start redis

Initialize database configuration

Before you start the server for the first time, you need to tell Diffux about your database setup. This is done by copying config/database.yml.example to config/database.yml and editing to fit your environment.

cp config/database.yml.example config/database.yml

When you are done with that, it's time to setup the database schema.

# create tables, load the schema, and run migrations
bundle exec rake db:setup

Running the server

Diffux is a Rails app, so if you are familiar with that web framework the following should be fairly straightforward.

bundle exec rails s

Rails runs on port 3000 by default, so you should be able to fire up your browser with the following URL:


Running a worker

Snapshot creation and comparing is handled asynchronously, through Sidekiq workers. To start a worker, run:

bundle exec sidekiq

Running Diffux on Heroku

Diffux can run on Heroku.

Diffux stores snapshots in Amazon Web Services (AWS) S3, so you will need to configure diffux with a Secret Key and a Access Key Id from Amazon. The best way to do this is to create IAM user for diffux and assign it to a group with the policy template "Amazon S3 Full Access". (This will help prevent large AWS bills in case your diffux credentials are compromised.)

Once you have your AWS credentials, you're all set!

Follow these steps:

# clone repo
git clone
cd diffux

# create and configure the heroku application
heroku create [your-diffux-app-name]
heroku addons:add heroku-postgresql
heroku addons:add rediscloud
heroku config:set PHANTOMJS_PATH=/app/vendor/phantomjs/bin/phantomjs \
  AWS_SECRET_KEY=[secret-key] \

# deploy!
git push heroku master

# initialize the database
heroku run rake db:migrate

# add a worker thread to take snapshots and generate compared images:
# This will cost you money if you leave it running!
heroku ps:scale worker=1

# done! you should now be able to access your application at
# http://[your-diffux-app-name]

Triggering sweeps

A sweep is a full set of snapshots taken for a project. You can trigger sweeps from a project in the web UI or through making a simple API call to /projects/{project_id}/sweeps/trigger. The API endpoint sends back a JSON object containing a url to a page showing the results of the newly created sweep. Remember: snapshotting is done asynchronously, so don't expect immediate results.

# Example of triggering a sweep using curl for a project with id=1
curl --header "Accept: application/json" \
     --header "Content-Type: application/json" \
     --data '{
               "title": "Deploy 1",
               "description": "Release Notes: Fixed layout bug",
               "delay_seconds": 20,
               "email": ""
             }' \

More about the JSON data:

key required description
title Yes A name/short description of the sweep, e.g. the name of the release/deploy.
description No A longer description, e.g. the full release notes.
delay_seconds No Number of seconds to delay the sweep with. This could be useful if you have an async release process.
email No An email address to send a message to when the sweep is ready (all snapshots taken and compared).


Released under the MIT License.