New
Multi-device comparison
Display multiple devices side by side and test them simultaneously. Single navigation, all breakpoints checked at once.
- Multiple devices in the same tab
- Shared navigation between devices
- Capture the whole in one image
Chrome, Firefox, and Edge extension
Smartphone and tablet simulator on computer
Test the mobile version of any site, check your responsive web design on 77 devices, and prepare your client demos in one click. Without leaving your browser.
1,000,000+ installations · 4.9/5 on the Chrome Web Store
Free installation in seconds · computer only
- 77preconfigured devices
- 14 brandsfrom Apple to Xiaomi
- 5 yearsadopted by devs and designers
- 162 → 2048 pxfrom smartwatch to desktop screen
Everything you need to test a responsive site, in a single panel
One click to switch to mobile view, one click to return to desktop. The rest behaves like on a real phone: touch gestures, zoom, landscape mode, PWA.
One-click video capture
WEBM, GIF, or MP4 for your demos and tutorials, recorded directly from the simulator, with or without a camera.
Transparent PNG captures
High-definition screenshots with a transparent background, ready for a presentation, mockup, or client email.
Realistic touch scrolling
Finger gestures are natively simulated: inertia, bounce, zoom. Navigation behaves like on a mobile.
Custom devices
Create and save your own devices with the exact screen resolution and viewport of your target.
Exact viewport and pixel density
Each model applies its real CSS resolution, pixel ratio, and User-Agent: media queries and breakpoints trigger like on the device.
Localhost, preproduction, all frameworks
Works on any URL, including a local server, and with React, Vue, Angular, WordPress, or a static site.
Dark mode and 10+ options
PWA mode, full screen, native keyboard, instant landscape toggle, dark theme for visual comfort.
Free PNG mockups
74 device mockups with transparent background, downloadable for free for your deliverables. View mockups
More than 77 ready-to-use devices
62 smartphones · 5 tablets · 9 desktop screens · 1 smartwatch
Old and new models, updated with each release. Each device includes its exact CSS viewport, pixel density, and User-Agent. Includes smartwatches, kiosks, and desktop screens.
Three ways to use it daily
Front-end development
Check your breakpoints without leaving the code
Switch from 320 px to 1280 px in one click during integration, with the touch gestures and zoom of a real mobile.
Agencies & freelancers
Client demos that make an impact
Show the site in a realistic device, then export the video or cropped capture for the report.
Project managers & QA
Test on the entire device fleet
Compare multiple models side by side, document anomalies with captures, and save hours of testing.
Mobile FIRST or the responsive mode of DevTools?
DevTools resize a window. Mobile FIRST replicates a device, and everything that comes with it.
| Feature |  | DevTools responsive mode |
|---|---|---|
| Preconfigured devices | 77, updated with each release | Short list |
| Realistic device display | Yes (browser & mockup) | No |
| Multiple simultaneous devices | Yes, side by side | No |
| Realistic touch gestures and zoom | Native simulation | Partial |
| WEBM, GIF, MP4 video capture | In one click | No |
| Captures with transparent mockup | Cropped PNG | Raw capture |
| Ready to show to a client | Yes | Debug tool |
Adopted for over 5 years by developers and designers
Our rating on the Chrome Web Store speaks for itself.
4.9/5 on 5,100 reviews
The best responsive testing extension on the market!
Super intuitive, lightweight, and packed with features. The touch scrolling is incredibly realistic, and having over 70 ready-to-use devices is fantastic. If you're a front-end developer or UI/UX designer, it's an essential tool. 5 stars all the way!
The cut-out captures go directly into client reports or my PowerPoints. It replaces hours of manual editing 😊. Very satisfied!
It's a really underrated extension. It does the job and even a bit more. I would even like to try the Pro version to enjoy their cool features, but the free version is already great.
It's not just for web developers: I would say it would be useful for anyone who owns a site and wants to know at any time what it looks like on different devices.
How to test your mobile site
Three steps, about thirty seconds, no account to create.
- 01 Install the extension On Chrome or Firefox, from the official store. Free, no account needed.
- 02 Open the page to test Production, preproduction, or localhost: one click on the icon and the page switches to mobile view.
- 03 Switch devices, capture Switch from one model to another, compare them side by side, export a capture or a video.
What is a mobile simulator?
A mobile simulator replicates, in your computer browser, the display conditions of a smartphone or tablet: CSS viewport, pixel density, User-Agent, and orientation. This allows you to see the mobile version of a site as a user would, without having to pull out a phone for every change.
Mobile FIRST covers 77 preconfigured models: iPhone simulator, Android emulator, iPad simulator, Samsung Galaxy tablets, and laptop screens. Each device applies its real resolution, so your media queries and breakpoints trigger exactly as on the hardware. Portrait/landscape toggle, zoom, and touch scrolling are simulated to mimic native behavior.
The extension applies to the open tab, regardless of the URL: production site, preproduction environment, or local server during development. It works with React, Vue, Angular, WordPress, and static sites, without configuration. Designed for front-end developers, designers, and QA teams, it is used to validate responsive web design and prepare client demos.
Frequently asked questions
Does the simulator replace testing on a real phone?
No. Mobile FIRST is very accurate for daily development, but a final test on a real device is still necessary for complete validation.
Which browsers does the extension work on?
Chrome, Firefox, Edge, Opera, Brave and any Chromium-based browser. Installation takes seconds and requires no account.
How many devices are available?
77 preconfigured devices: 62 smartphones, 5 tablets, and 10 desktop screens and smartwatches. You can also create your own devices with the resolution and viewport of your choice.
Can I record a video of mobile navigation?
Yes, in one click, in WEBM, GIF, and MP4 formats. PNG screenshots are exported with a transparent background.
Can we test a site on localhost or preproduction?
Yes. The extension applies to the current tab, regardless of the URL: production, preproduction, or a local server during development.
What is the difference with the DevTools responsive mode?
DevTools resize a window for technical inspection. Mobile FIRST replicates the device: realistic frame, touch gestures, zoom, multiple models side by side, export capture and video.
Are new models added?
Yes, the list is regularly updated as manufacturers release new screens.
Test your site on 77 devices, directly in your browser
Without buying a single phone, without creating an account.
- 77 devices available upon installation
- Real viewport, User-Agent, and touch events
- Also works on localhost and in pre-production
- Exportable screenshots and videos
Free · 4.9/5 on 5,100 reviews
1,000,000+ users