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Use Firefox’s Responsive Design Mode (RDM) to emulate an iPhone-sized viewport and capture it: open the page, press Ctrl+Shift+M on Windows or Linux, or Cmd+Opt+M on macOS, choose or create an iPhone 14 device profile, set its CSS viewport dimensions, and click the camera button. The result is a screenshot of an emulated responsive view—not proof of pixel-identical rendering on an actual iPhone.
Set up the iPhone 14 viewport in Firefox
- Open the page in desktop Firefox. Navigate to the page you want to test.
- Open Responsive Design Mode. Press Ctrl+Shift+M on Windows or Linux, or Cmd+Opt+M on macOS. You can also open it from the Developer Tools toolbar. Firefox documents an initial responsive content area of 320 × 480 CSS pixels.
- Choose a device profile. Open the device selector and look for iPhone 14. Presets can change, so do not assume it is installed. Mozilla’s device guidance includes iPhone 14 among previous-generation devices relevant to the RDM list, but that does not guarantee a preset is available. If it is missing, use Edit list if available, or create a custom device profile.
- Set the dimensions and device behavior. Enter the intended width and height in CSS pixels, choose portrait or landscape, and set DPR, user agent, and touch simulation as needed. Firefox lets you edit the displayed dimensions or drag the viewport. Save a custom profile if you will reuse these settings.
- Reload after changing emulation when needed. Some page handlers are attached only at load time. If a user-agent or touch-dependent behavior does not change, reload the page after changing the relevant RDM setting.
- Inspect the layout and capture it. Check the page at the selected viewport, then click RDM’s camera button. Firefox saves the viewport screenshot to its default download location unless its clipboard behavior is configured.
Use CSS viewport dimensions, not the phone’s panel resolution
Apple lists the iPhone 14 display as 2532 × 1170 pixels at 460 ppi. Those are physical display specifications, not the CSS viewport width and height to enter in RDM (Apple iPhone 14 technical specifications). CSS viewport dimensions determine responsive layout; device pixel ratio (DPR) describes the relationship between CSS pixels and device pixels and can affect density-sensitive rendering and image selection.
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The sources here do not establish an exact iPhone 14 CSS viewport and DPR value to use as a universal preset. Read the properties shown for the selected device in Firefox, or verify the values on hardware. Do not infer CSS dimensions from the panel resolution or treat an unverified DPR value as authoritative. Mozilla documents that a specific DPR can be set with a custom device (Firefox Responsive Design Mode documentation).
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- Responsive layout or a screenshot: Prioritize the CSS viewport width and height, then choose the required orientation.
- Density-sensitive images or rendering: Set the intended DPR as well as the viewport dimensions.
- Touch-conditioned interface: Enable touch simulation. Firefox translates mouse events into touch events while it is enabled; this is useful for checking touch-specific UI, but does not reproduce every detail of a real device.
- User-agent-dependent behavior: Consider the emulated user agent, then reload if the page does not react to the change. Mozilla notes that when an iPhone is selected, Firefox identifies itself as Safari. This is user-agent emulation, not Safari running on iOS (Mozilla’s RDM documentation).
- Actual iOS behavior: Check on an iPhone or an iOS simulator if the result depends on iOS rendering, browser chrome, input behavior, or safe-area details. Desktop Firefox RDM is a responsive-testing aid, not a full iOS simulator. Apple also documents differences between iOS-family rendering and macOS in its Responsive Design Mode guidance.
Check the page’s viewport metadata
If a layout does not switch to its narrow-screen breakpoints, inspect the page’s viewport meta element before assuming the selected RDM dimensions are wrong. MDN recommends <meta name="viewport" content="width=device-width, initial-scale=1"> so the layout viewport matches the device width. Without suitable viewport metadata, a mobile layout may be evaluated against a wider virtual viewport (MDN: The viewport meta element; MDN: Responsive web design).
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Capture a viewport or the whole page
Use the RDM camera button for the emulated viewport currently displayed. It is the right choice when the artifact should show the page at the selected iPhone-sized dimensions. If you need the entire document rather than the visible test viewport, use Firefox’s separate screenshot interface and select Save full page; Mozilla documents that workflow separately (Mozilla Support: Take screenshots in Firefox).
Or skip the browser setup
For a one-request screenshot instead of configuring a local browser, ScreenshotNeo accepts a URL and returns an image or PDF. See the ScreenshotNeo API documentation for parameters and options.
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curl -G "https://api.screenshotneo.com/v1/shot" -d access_key=YOUR_API_KEY --data-urlencode url=https://stripe.com -o shot.webpScreenshotNeo removes cookie and consent banners, newsletter popups, and chat widgets before capture; bot checks, blank pages, failed loads, timeouts, and cache hits are not billed. Its MCP server lets AI agents take screenshots, and the Free plan includes 1,000 shots a month with no card; paid plans start at $5 for 3,000 shots. See ScreenshotNeo and sign up for 1,000 free screenshots a month, with no card required.
Troubleshooting
- iPhone 14 is not in the selector: Create a custom device or edit the device list if that option is available. Set the viewport and DPR from verified device properties rather than guessing from screen resolution.
- The page still looks like a desktop layout: Check the CSS viewport dimensions and the page’s viewport meta element. Then reload after changing emulation settings if the page may have bound its handlers at load time.
- Touch controls do not respond as expected: Confirm touch simulation is enabled and reload. Treat it as an emulation of touch events, not as a substitute for testing on the target platform.
- The saved image shows only part of the document: The RDM camera captures the viewport. Use Firefox’s screenshot interface and Save full page for the whole document.
- The screenshot differs from a real iPhone: Confirm that the viewport, orientation, DPR, and any needed touch or user-agent settings match your test. For platform-specific rendering or behavior, validate on an iPhone or iOS simulator.
Frequently Asked Questions
Do I need an iPhone 14 to test this viewport in Firefox?
No. Responsive Design Mode can emulate a viewport on desktop Firefox; a physical phone is optional for validating actual iOS behavior.
Does Firefox’s iPhone selection run Safari?
No. Mozilla says Firefox can identify itself as Safari when an iPhone is selected, but that is user-agent emulation, not Safari running on iOS.
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