Emulate or Test? There are emulators to show you how it will look without any judgement and there are tools online to tell you if there are any issues you might not see visually. It depends on your objective which you should use.

I want to test if the website is mobile responsive or not.

Now I use chrome and FFox dev tool, and then I check on my actual phone, and results are not consistent.

Both seeing results visually and errors are fine.

I don't believe there is an emulator that does all, especially with all the different screens and, of course, operating systems. Not everyone has the latest os installed, for varying reasons, and some have different flavours, depending upon the hardware manufacturer.

You can only get a best guess with the tools available.

Actually, best solution is too simply test on my mobile phone, it's archaic, but it works!

First I check with dev tools chrome, and then I check again on my mobile...!

Actually, best solution is too simply test on my mobile phone, it's archaic, but it works!

Absolutely. The only problem is having a selection of OS and screen sizes.

Additionally, you may have a harder time testing Android than iOS devices, because Android is a more open platform that has many different allowable levels of implementation, as well as different UIs. Apple, on the other hand, more strictly limits where the developer can go.

For each platform (or major variant) you're going to have compatibility issues, a range of security issues, perhaps a range of interface choices. There's also a range of device types, that's growing... including very large large-screen devices. and some with voice interfaces.

I was at a group presentation tonight at a private home, which included projection and sound, and an internet connection... and someone in the audience noticed that there was music playing softly, which was a distraction. As we figured out what to do to turn it off, the hostess quipped: "Don't talk to Alexa, whatever you do," which got a lot of laughter (except perhaps from the developers in the audience, who will be dealing with competing voice inputs before too long).

Best thing for testing is a range of actual mobile phones, pulled from members of the development group and friends... and perhaps some devices bought used as part of the testing arsenal.

Keep us posted on what you do. It would be a major help.

Have you tried the built in browser tools, such as Firefox'x "responsive design mode"? (Unsure by your original post as it refers to HTTP rather than layout)

I've used Genymotion (on Linux) to reasonable effect, not sure if it's essentially required for emulating browser layouts

For checking layout issues my 'when all else fails' tools are at the w3c validation sites:
HTML: [validator.w3.org...]
CSS: [jigsaw.w3.org...]
because their detailed reports can tell you what, why and what it should be. If it is standards compliant, it looks the way things should look on the device, even if it looks different on different devices.

And then there is Fetch as Google to see if their bot 'sees' the page as you expect.

I don't know of any website online that accurately offers versions of platforms and browsers that are more useful than the developer tools in FF and Chrome.

I want to test if the website is mobile responsive or not.

What do you need an emulator for, then? Resize your browser window and you can see if things rearrange themselves as desired. (Back when responsive @media rules first became popular, there was an amusing sample page that simply changed the background color based on window width. It illustrated the concept very neatly.)

I suspect you don’t actually mean “responsive”, though.

Code it simple (responsive) and deal with the fact that you cannot control all pixels. There are hardware based pixels between devices that no emulator can reproduce on YOUR hardware. Most of the time it is THAT CLOSE, but for some devices it is NO CIGAR.

Live with it.

You can't please EVERYBODY (and if you do, you just might not please everyone else!).

Pick your battles and go from there.

Err conservative in your designs. Keep it Simple, Simple!