In bug 1172309 we're tracking using the device catalogf for RDV. For Android devices we can't / don't want to track all devices. As a developer I should be able to somehow define custom device definitions with arbitrary values of the correct type for the supported properties, for example: { name: "Geeksphone Keon", // String width: 320, // int height: 480, // int pixelRatio: 1, // float userAgent: "Mozilla/5.0 (Mobile; rv:28.0) Gecko/28.0 Firefox/28.0", // string touch: true, // boolean }, We should store these and allow import / export of them.

Additionally - as a developer I should be able to clone an existing device definition and 'save as' a new one.

This is possible via about:config

(In reply to Tim Nguyen [:ntim] from comment #2) > This is possible via about:config Yup - just want to offer a better user experience for that. Here's a use case: I have a weird android phone I want to emulate - say one that is popular in some countries but doesn't make the global top list. I'd really like to be able to load a similar device, click 'copy', Give it a name and adjust the parameters as needed, then hit 'save'.

The device list is now stored in IndexedDB, so it's a bit harder to tweak the actual data just from about:config. If you are in dire need of a customized device set before a UI is added here, you could change the pref "devtools.devices.url" to point at your own JSON file.

Another related thing that is lost with the new RDM are the previously user defined devices (well, not exactly devices but just dimensions plus a name). It was strange that just an update forgot my presets, I think they must be imported from the previous settings. thanks

In bug 1321675, the "minimal" UI turned into enough of a UI to create a complete device, so be sufficient to cover the needs here as well. For the moment, it doesn't convert data from old RDM. Currently, this doesn't seem like a major issue to me, as it's just a few names and numbers, plus the new version has additional fields that would need to be set anyway. Feel free to file a separate bug if it's important to you.

Doc updated here: https://developer.mozilla.org/en-US/docs/Tools/Responsive_Design_Mode