The Screen Resolution Simulator is a free online tool that lets you preview how any website looks at different screen sizes and resolutions — from mobile phones to 4K desktop monitors. With over half of all web traffic coming from mobile devices, testing responsive behavior across multiple screen sizes is essential for any web designer or developer.

Instead of physically owning multiple devices or resizing your browser window manually, this tool renders a live preview of any URL at the exact dimensions you specify.

How to Test at Different Resolutions

• Enter the website URL you want to test
• Choose a preset device size (iPhone, iPad, desktop, etc.) or enter custom dimensions
• Click Preview — the site renders inside a frame at the selected size
• Switch between sizes to compare the responsive layout

Common Screen Resolutions to Test

• 320x568 — iPhone SE (small mobile)
• 375x667 — iPhone 6/7/8
• 768x1024 — iPad (tablet)
• 1366x768 — Most common laptop display
• 1920x1080 — Full HD desktop

What to Look For

• Text remains readable at all sizes
• Buttons and links are tappable on mobile
• Images scale proportionally
• No horizontal scroll bar on mobile
• Navigation collapses to hamburger menu on small screens

Free, no login required.