Open a new Firefox tab or window, and type about:config (If a warning message comes up, just click OK).
Create a new entry devtools.responsiveUI.presets - right click and chose 'new' then 'string' - under enter the preference name type devtools.responsiveUI.presets then hit OK. When the enter string box appears simply add the presets.
Restart Firefox.
Obs: It's devtools.responsiveUI.presets, not devtools.responsive.UI.presets.
| [{ | |
| "name": "CGA: 320x200", | |
| "width": 320, | |
| "height": 200 | |
| }, { | |
| "name": "QVGA: 320x240", | |
| "width": 320, | |
| "height": 240 | |
| }, { | |
| "name": "CIF: 352x288", | |
| "width": 352, | |
| "height": 288 | |
| }, { | |
| "name": "SIF: 384x288", | |
| "width": 384, | |
| "height": 288 | |
| }, { | |
| "name": "HVGA: 480x320", | |
| "width": 480, | |
| "height": 320 | |
| }, { | |
| "name": "VGA (NTSC): 640x480", | |
| "width": 640, | |
| "height": 480 | |
| }, { | |
| "name": "PAL: 768x576", | |
| "width": 768, | |
| "height": 576 | |
| }, { | |
| "name": "WVGA: 800x480", | |
| "width": 800, | |
| "height": 480 | |
| }, { | |
| "name": "SVGA: 800x600", | |
| "width": 800, | |
| "height": 600 | |
| }, { | |
| "name": "WVGA (NTSC): 854x480", | |
| "width": 854, | |
| "height": 480 | |
| }, { | |
| "name": "PAL: 1024x576", | |
| "width": 1024, | |
| "height": 576 | |
| }, { | |
| "name": "WSVGA", | |
| "width": 1024, | |
| "height": 600 | |
| }, { | |
| "name": "XGA: 1024x768", | |
| "width": 1024, | |
| "height": 768 | |
| }, { | |
| "name": "1152x768", | |
| "width": 1152, | |
| "height": 768 | |
| }, { | |
| "name": "XGA: 1152x864", | |
| "width": 1152, | |
| "height": 864 | |
| }, { | |
| "name": "WXGA: 1280x600", | |
| "width": 1280, | |
| "height": 600 | |
| }, { | |
| "name": "HD 720: 1280x720", | |
| "width": 1280, | |
| "height": 720 | |
| }, { | |
| "name": "WXGA: 1280x768", | |
| "width": 1280, | |
| "height": 768 | |
| }, { | |
| "name": "WXGA: 1280x800", | |
| "width": 1280, | |
| "height": 800 | |
| }, { | |
| "name": "SXGA: 1280x1024", | |
| "width": 1280, | |
| "height": 1024 | |
| }, { | |
| "name": "980x1280", | |
| "width": 980, | |
| "height": 1280 | |
| }, { | |
| "name": "Microsoft Surface RT: 320x240", | |
| "width": 1366, | |
| "height": 768 | |
| }, { | |
| "name": "1400x900", | |
| "width": 1400, | |
| "height": 900 | |
| }, { | |
| "name": "1400x960", | |
| "width": 1400, | |
| "height": 960 | |
| }, { | |
| "name": "SXGA+: 1400x1050", | |
| "width": 1400, | |
| "height": 1050 | |
| }, { | |
| "name": "1400x1080", | |
| "width": 1400, | |
| "height": 1080 | |
| }, { | |
| "name": "1600x900", | |
| "width": 1600, | |
| "height": 900 | |
| }, { | |
| "name": "UXGA: 1600x1200", | |
| "width": 1600, | |
| "height": 1200 | |
| }, { | |
| "name": "WSXGA+: 1680x1050", | |
| "width": 1680, | |
| "height": 1050 | |
| }, { | |
| "name": "1920x900", | |
| "width": 1920, | |
| "height": 900 | |
| }, { | |
| "name": "HD 1080: 1920x1080", | |
| "width": 1920, | |
| "height": 1080 | |
| }, { | |
| "name": "WUXGA: 1920x1200", | |
| "width": 1920, | |
| "height": 1200 | |
| }, { | |
| "name": "2K: 2048x1080", | |
| "width": 2048, | |
| "height": 1080 | |
| }, { | |
| "name": "QXGA: 2048x1536", | |
| "width": 2048, | |
| "height": 1536 | |
| }, { | |
| "name": "WQHD: 2560x1440", | |
| "width": 2560, | |
| "height": 1440 | |
| }, { | |
| "name": "WQXGA: 2560x1600", | |
| "width": 2560, | |
| "height": 1600 | |
| }, { | |
| "name": "QSXGA: 2560x2048", | |
| "width": 2560, | |
| "height": 2048 | |
| }, { | |
| "name": "2160p: 3840x2160", | |
| "width": 3840, | |
| "height": 2160 | |
| }, { | |
| "name": "4k: 4096x2160", | |
| "width": 4096, | |
| "height": 2160 | |
| }, { | |
| "name": "4320p: 7680x4320", | |
| "width": 7680, | |
| "height": 4320 | |
| }, { | |
| "name": "8k: 8192x4608", | |
| "width": 8192, | |
| "height": 4608 | |
| }, { | |
| "name": "8640p: 15360x8340", | |
| "width": 15360, | |
| "height": 8640 | |
| }] |