Visual regression testing: an automated process for detecting unintended changes in the appearance of a user interface, by comparing a reference state (baseline) with a current state, making it possible to identify layout, color, typography, or spacing regressions before they reach production. A common definition in front-end QA engineering.
Diffy is one of the tools that agencies and web teams discover when they look for a way to check a site before going live. Its principle is simple to explain: capture the same pages on two environments, production and staging for example, and show what differs.
Delta-QA starts from somewhere else. Instead of comparing two environments, it replays a recorded journey (login, form, cart) and compares each step with its reference the way a human eye would: it spots the elements that changed and names them in the report.
Both tools answer the same worry: "did my update break something on screen?" This comparison explains what each one actually does as of 10/2026, where each excels, and which one fits the way you work.
All our comparisons, based on verifiable criteria: Alternatives and comparisons.
Your journeys checked step by step, without writing code? Delta-QA records the scenario in the browser and tells you which element changed, with a free account and no credit card. Try Delta-QA for free →
What Diffy Is: The Environment Comparison Approach
Diffy is an online visual regression testing service, designed primarily for agencies managing many sites, notably on WordPress and Drupal. Its central principle is comparison between environments.
The Concept: Prod vs Staging vs Dev
You have your site in production and a version on staging with the latest changes. Diffy captures the same pages on both and shows you the differences side by side. If staging looks like production, your changes broke nothing on screen; otherwise, Diffy shows you where to look.
Diffy also offers scheduled monitoring (comparisons run at regular intervals to spot an unexpected change) and a comparison between live pages and exported Figma mockups.
What Diffy Does Well
Diffy has tackled the classic sources of noise in image comparison. As of 10/2026, its home page highlights:
- freezing of dynamic elements and replacement of content that changes on every visit, rather than simple masks;
- handling of sticky elements (fixed headers) and detection of vertical shifts, so that a block inserted at the top of the page doesn't make everything below it "different";
- AI-generated difference summaries, which group changes by type (layout, content, style) and rank them by impact;
- a skill for Claude, which lets you launch a comparison from the code assistant;
- integration with local environments (DDEV, Lando, Docksal), with CI, and an on-premise installation.
Getting started is advertised as taking about twenty minutes. For an agency that must check dozens of sites after every CMS update, it's a tool tailored to the need.
What Diffy Requires
Comparing between environments assumes you have at least two comparable environments. If staging and production don't display the same data, part of the differences comes from the data and not from the code, and you have to neutralize it (freezing, simulated content) or sort it out by hand.
Diffy works in terms of captured pages. It is very effective for broadly covering a site page by page; it is less natural for checking what happens in the middle of a journey, after a login or through a multi-step form.
What Delta-QA Is: Regression Testing by Recorded Journey
Delta-QA is aimed at teams who want to check their critical journeys on every version, without writing tests.
A Recorded Scenario, Replayed on Every Version
You open your site in Delta-QA and walk through the scenario like a user: login, search, add to cart, payment. Each step becomes a checkpoint. On the next version, Delta-QA replays the journey in a real browser and compares each step with its reference.
There is no need for a second environment: the reference is the validated state of your own site. You can run the scenario on staging, on a pre-production environment, or on production.
A Comparison That Simulates the Human Eye
Delta-QA doesn't compare two images. It compares the elements of the page and tells you what actually moved: a button's color, a margin or padding, an element's position, a block that overflows or disappears. The report doesn't show a red area to interpret: it names the element and describes the change. You judge each difference, intended or bug, and the reference moves forward with you.
No-Code: Visual Testing Open to the Whole Team
The developer knows what they changed. But it's often the QA who checks that nothing is broken, the product owner who validates the rendering, the designer who judges adherence to the mockup. With Delta-QA, everyone records and replays their own journeys without depending on a developer.
Delta-QA runs as SaaS or, with the On-Premise offer, on your infrastructure; the On-Premise offer can be evaluated through a free one-month POC. The comparison is done on Chromium today; Firefox and WebKit are planned.
One reference per journey, not a second environment to keep in sync. Delta-QA replays your scenarios and names each element that changed, no-code and no credit card. Try Delta-QA for free →
Direct Comparison: Diffy vs Delta-QA
What Is Compared
Diffy compares page captures: between two environments, with a previous capture, or with a Figma mockup. It combines image comparison with processing that reduces noise (freezing dynamic elements, detecting shifts) and AI summaries.
Delta-QA compares the steps of a journey with their reference, as a human eye would. The result is a list of changes tied to elements of the page.
What You Read in the Report
With Diffy, you see the captures side by side and the areas that differ, with a summary that groups and prioritizes the changes.
With Delta-QA, you read a description of each changed element: "the Pay button went from blue to green", "the container margin went from 24 to 16 pixels". It can be passed directly to the developer concerned.
Prerequisites
Diffy works best with two comparable environments, or with a reference capture taken earlier.
Delta-QA works with a single environment: you record the journey, the first run serves as the reference, then each version is compared with that reference.
Who Uses It
Diffy targets developers, QA people, and project managers in agencies. Its web interface and its integration with local tooling or Claude suit technical profiles who manage many sites.
Delta-QA targets the whole product team, including people who don't code: manual QA testers, product owners, project managers.
Test and CI Integration
Diffy offers CI automation in its paid plan.
Delta-QA now has an SDK, Vision, for Playwright (TypeScript/JavaScript). One line per page to check is enough: an unreviewed difference makes the test fail, and the CI log gives the link to the report. Tests written in code and no-code scenarios live in the same space. Delta-QA also offers an MCP server to drive your scenarios from a code assistant.
Pricing
As of 10/2026, Diffy's pricing page shows a free plan of 500 captures per month (two environments, one month of history), then a Pro plan from $67 per month billed annually for 2,000 captures, with CI, multiple environments, and six months of history.
Delta-QA starts with a free account, no credit card; the paid plans are detailed on the product's pricing page.
When to Choose Diffy
Diffy is a very good choice if you are an agency or a web team managing many sites, notably on WordPress or Drupal, and you want to quickly check lists of pages between staging and production after every update.
It is also relevant if you want to monitor a site at regular intervals, compare pages with Figma mockups, or launch comparisons from Claude or your local environment.
When to Choose Delta-QA
Delta-QA is the right choice when what matters is not a list of pages but journeys: a checkout funnel, a sign-up, a back-office behind a login. Each step is verified, in the order the user experiences it.
It's also the right choice when the people verifying the application don't code, and when you want a report that names the modified element rather than an area to interpret. To go further on the approach, see our guide to regression testing.
Ready to check your critical journeys on every version? Record your first scenario with Delta-QA, free and without a credit card. Try Delta-QA for free →
FAQ
Is Diffy open source?
No. Diffy is an online service with a free plan and a paid Pro plan; its home page also mentions an on-premise installation. It shouldn't be confused with open source tools like BackstopJS, which you install and maintain yourself.
Can Diffy and Delta-QA be used together?
Yes, they complement each other: Diffy to sweep many pages between environments or monitor a site, Delta-QA to verify critical journeys step by step. If you want to evaluate Delta-QA, you can also run both in parallel on the same pages for the time it takes to compare the reports.
Does Delta-QA detect color changes?
Yes, for the elements of the page (background, text, border): the report indicates which element changed color. A change inside an image (a logo, a photo) falls under the image's content and is not described in the same way.
How long does each tool take to set up?
Diffy advertises getting started in about twenty minutes. Delta-QA is operational in a few minutes for a first scenario: you create an account, record a journey, and replay it.
How do I switch from Diffy to Delta-QA?
There is no data to convert: Diffy's captures and Delta-QA's references are of a different nature. You record in Delta-QA the journeys that match the pages you were monitoring, the first run serves as the reference, and you're up and running.
Which tool for a WordPress or Drupal site?
Both work on any site accessible in a browser. Diffy highlights its use by WordPress and Drupal agencies and its integrations with the local environments of those ecosystems. Delta-QA is independent of the CMS: it records and replays what the user sees.