Alt+cmd+m FTW Rated 5 out of 5 stars

For those having trouble: try alt+cmd+m instead - that worked for me. Default presets are kinda limited, but looks easy enough to add your own. Very handy extension as it also manages height, not just width. Thanks Carlos!

Unable to get this work work either... Rated 1 out of 5 stars

Sorry Carlos. I'm unable to get this to work either.

Clicking "Install Presets" does nothing, nor does CTRL + SHIFT + M. I would have sent you an email to trouble-shoot prior to leaving a 1-start review, but the email link on your homepage is a 404 (not working either).

Hopefully you can get this working. Looks promising!

Mac OS 10.7.5, Firefox 36.0.1

Rated 5 out of 5 stars

The low reviews are from people who don't necessarily know what they're doing! Works great! Steps to use:

1) Install Add-on
2) Go to Tools > Add-ons in FF
3) Click the Install Presets button
4) Find a site, and press CTRL+SHIFT+M to switch to the responsive UI tester

Awesome!

Just what I needed Rated 5 out of 5 stars

thanks

How do I use this? Rated 1 out of 5 stars

I couldn't find how to use this extension, uninstall

doesn't work Rated 1 out of 5 stars

at all