Responsive tool recommendations needed

[Gilead]

I had been using firesizer, responsive layout for firefox to make sure my responsive sites worked properly. The new web developer responsive design mode in firefox doen't work as well as the previous version. After weeks of tweaking a site to get it to look right locally, when I put it on the server and looked at it, it was completely messed up. Is there a proven responsive site plug in or standalone that anyone can recommend?
Would prefer firefox compatibility. Thanks!

[c4cyber]

I check using Chrome web development tool to test my site in responsive and mobile view. Its free to use and no need of any extra plugin.

[not2easy]

The only tool available for Firefox current version is the Web Developer Toolbar and it does offer a responsive viewer. I'm very unhappy about many of the useful tools that no longer function with FF's move toward imitating Chrome. All their add-ons or extensions seem to be aimed at image and content copying, ad blocking and so-called privacy tools that only seem to automate settings changes. It is not nearly as useful as it once was imho.

[pavanear]

LambdaTest: This is a cross-browser testing tool which enables users to test more than 22,000 browser, mobile, and OS combinations. You see a separate tab for Responsive testing below Visual UI Test, where you can see the responsiveness of your website on various devices and screen sizes.

[keyplyr]

@Gilead - I certainly wouldn't use anything Firefox based for testing display. Besides the diehard tech crowd (many here at WW) the Firefox browser is not used much by the average user.

Firefox also has spacing issues the way it displays CSS2 & CSS3. Both Chrome & Edge do a much better job of displaying web standards.

Also since most users choose the default browser that comes with their device, as a web developer it's wise to see your pages the way they do... that's using Chrome, Edge and Safari.