
Polypane
Responsively
browserling
Browsershots
CrossBrowserTesting
Sauce Labs
Litmus
The browser for designers and developers

BrowserStack
TestMu AI (Formerly LambdaTest)
browserling
Browsershots
CrossBrowserTesting
Blisk
Can I use
Responsive Tool is a free responsive website checker — test your website on mobile, tablet, and desktop at once, no signup, no download.

Which is more popular?
Based on our record, Sizzy seems to be more popular. It has been mentioned 19 times since March 2021.
Website, pricing, platforms and company facts side by side.
|
|
|
|
|---|---|---|
| Website | sizzy.co | responsivetool.com |
| Pricing | ||
| Company | — | Startup from the United States · 1 - 9 employees · 2026 |
| Listed in |
In their own words, as submitted to SaaSHub.


No description of Sizzy yet.
Responsive Tool lets you paste a URL and preview it across real device viewport sizes — phone, tablet, desktop, or a custom width — side by side in live, interactive iframes you can scroll and click through, not static screenshots. It includes 20+ named device presets plus one-click jumps to...
What each product offers, as listed by its team.


Possible disadvantages
An editorial look at what each product does well and who it suits.


Overall verdict
Why this product is good
Recommended for
No analysis of Responsive Tool yet.
Walkthroughs and reviews on video.
Should every Frontend Developer own this software? Checking out 'Sizzy'
More videos
Responsive Tool — Test Your Website on Mobile, Tablet & Desktop Side by Side
How often each product is chosen within a category, 0–100% relative to the other.


As answered by people managing Sizzy and Responsive Tool.
Responsive Tool's answer:
Next.js, React, TypeScript, Tailwind CSS, deployed on Cloudflare Workers.
Responsive Tool's answer:
It renders live, interactive iframes side by side — not static screenshots — across real device viewport sizes, with one-click jumps to common CSS breakpoint boundaries (e.g. 767/768/769px) so you can test right at the edge, not just round numbers. You can also copy a link that reproduces your exact comparison (same URL, same devices, same custom widths) for anyone else to open.
Responsive Tool's answer:
Most cross-browser/device testing platforms (BrowserStack, LambdaTest, etc.) are built for QA teams running automated test suites across real device clouds — paid, feature-heavy, and overkill for a quick visual check. Responsive Tool is free, requires no signup, and is built specifically for one thing: seeing how a page looks across device sizes at a glance.
Responsive Tool's answer:
Indie developers, freelancers, and small teams who need a fast, free way to sanity-check a responsive layout without setting up a device lab or a paid testing platform.
Share your experience with using Sizzy and Responsive Tool. For example, how are they different and which one is better?
Recommendations tracked on public social media and blogs since March 2021.


Seems quite similar to https://sizzy.co/. - Source: Hacker News / over 1 year ago
Just so you know Sizzy exists as well and has been around for a while so you would competing with them as well. Source: almost 3 years ago
I would like to introduce you to Sizzy. Source: over 3 years ago
Tracking Responsive Tool since Oct 2026.
When comparing Sizzy and Responsive Tool, you can also consider the following products.

The browser for ambitious web developers that want to 5× their quality and efficiency.
Compare Polypane to Sizzy or Responsive Tool:

BrowserStack is a software testing platform for developers to comprehensively test websites and mobile applications for quality.
Compare BrowserStack to Sizzy or Responsive Tool:

Develop responsive web-apps 5x faster!
Compare Responsively to Sizzy or Responsive Tool:

World’s first full-stack Agentic AI Quality Engineering platform.
Compare TestMu AI (Formerly LambdaTest) to Sizzy or Responsive Tool:

Live interactive cross-browser testing from your browser.
Compare browserling to Sizzy or Responsive Tool:

Browsershots makes screenshots of your web design in different browsers.
Compare Browsershots to Sizzy or Responsive Tool: