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JLineup is a tool which is useful for automated visual regression tests of web pages, especially in continuous delivery pipelines. It can be used as a simple command line tool or as a small web service which is controlled via REST API.

JLineup shoots and compares screenshots of a web page at two consecutive points in time. It does a pixel by pixel comparison of both runs and generates a HTML and a JSON report. Behind the scenes, it uses Selenium and a browser of choice (currently Chrome, Chromium and Firefox are supported).

JLineup has no other dependencies than web browser (Firefox or Chrome/Chromium) and a JVM. Experimental: There's also a self-contained Linux AMD64 build of the CLI version that doesn't even require a JVM.


Let's take this little example config for a check of during a deployment:

  "urls": {
    "": {
      "paths": [ 
      "devices" : [ {
        "width" : 850,
        "height" : 600,
        "pixel-ratio" : 1.0,
        "device-name" : "DESKTOP",
        "touch" : false
      }, {
        "width" : 1000,
        "height" : 850,
        "pixel-ratio" : 1.0,
        "device-name" : "DESKTOP",
        "touch" : false
      }, {
        "width" : 1200,
        "height" : 1000,
        "pixel-ratio" : 1.0,
        "device-name" : "DESKTOP",
        "touch" : false
      } ]
  "wait-after-page-load" : 0.5,
  "browser" : "chrome-headless"

JLineup runs before and after the deployment and generates a report like this:

Screenshot of HTML report

There's also a JSON report, which is great if you want to check things by script:

Example JLineup JSON Report

Quick Howto

JLineup CLI comes as executable Java Archive. Java 17 or higher has to be available to run it.

Open a terminal and download it like this:

wget -O jlineup.jar

Then type

java -jar jlineup.jar --help

to see the command line help.

See the CLI documentation for more details and a small tutorial.

Integration example

This is an example, how JLineup can be helpful in your automated build and deploy pipeline. Let's assume, this is part of a continuous integration pipeline:

Pipeline exampe

Browser Compatibility

JLineup 4.11 was tested successfully with

  • Chrome 124.x
  • Firefox 126.x

Chrome or Firefox have to be installed on the system if you want to use one of them.


JLineup as CLI tool

JLineup as web server

JLineup Job Configuration

Third Party Libraries

JLineup uses some third party tools and libraries

Edison Microservice
Spring Boot
GraalVM Community Edition
Image Compare Viewer
Google Fonts

Some code from Pixelmatch was ported to Java for JLineup.


Some code from Looks-same was ported to Java for JLineup.

Historic Facts

JLineup is a configuration compatible replacement for Lineup, implemented in Java. The original Lineup was a Ruby tool, but is not maintained any more.

Credit for original Lineup goes to Finn Lorbeer.


If you have questions or proposals, please open an issue or write an email to marco DOT geweke AT