Free tools / Mobile preview tool
Mobile preview tool
Paste a URL, pick a device. Where the site allows it, you get a live, interactive preview at that exact viewport — iPhone, Android, iPad or a custom size. Where it doesn't (most sites that block embedding do it on purpose), this falls back to a real screenshot automatically.
Why a resized browser window isn't the same test
Dragging your desktop browser narrow shrinks the viewport, which is
enough to trigger CSS media queries — but it doesn't change what site
your visitor's user-agent reports, and some sites, especially
older ones, still serve a genuinely different mobile template or
redirect to an m. subdomain based on that. The live
preview here has the same limitation a resized window does — it's
still your own browser's user-agent, since a page can't override that
for a frame it's embedded in. The screenshot fallback doesn't have
that gap: it sends a real mobile Safari user-agent for mobile
viewports, so between the two, this tool catches both kinds of
"different on mobile" — the responsive-CSS kind and the
branches-on-user-agent kind — even though only one of them does it on
every single check.
What to actually look for
The obvious checks are text wrapping, images overflowing their container, and navigation collapsing into a menu that actually works. Less obvious, and worth the "Full page" toggle for on pages where it renders cleanly: tap targets close enough together to mis-tap, a hero section so tall it pushes everything else below the fold, and forms where a label and its input end up on different lines in a way that reads fine on desktop and confusing on a 375px-wide screen.
Seeing the moment it actually breaks
A screenshot shows you the end state — it won't show you a user fumbling a mis-sized tap target three times before giving up, or rage-tapping a button that visually looks clickable but isn't. Session replay shows you that: the actual session, on the actual device, as video and as a transcript your agent can read. This tool tells you what mobile looks like; session replay tells you what happened when a real person used it.
FAQ
How is this different from resizing my browser window?
Resizing your desktop browser only changes the viewport width — it doesn't change the user-agent, so a site that branches on user-agent (not just CSS media queries) can look different to it than to a real phone. The live preview here still uses your own browser's user-agent (that's a real browser limitation, not something a page can override for an embedded frame); the screenshot fallback uses a real mobile Safari user-agent instead, so between the two, both kinds of "different on mobile" get covered.
Why do some sites show a live preview and others a screenshot?
Most sites can be embedded in an iframe, which gives a genuinely live, interactive preview — real scrolling, real hover states, no rendering lag. Some sites block that on purpose, via an X-Frame-Options or Content-Security-Policy header, usually as a clickjacking defense. This tool checks for that upfront and falls back to a real headless-browser screenshot automatically when it detects a block, rather than showing you a blank frame.
Is the screenshot fallback a full-page capture or just what's visible on load?
Above-the-fold by default — the first screenful at your chosen viewport, which is the most reliable capture across arbitrary sites. There's an optional "Full page" toggle for the screenshot fallback that scrolls the whole page into one image, but pages built with scroll-driven or sticky-positioned animations can render that badly (the captured height reflects the scroll track, not the visible content), so it's opt-in rather than the default. It doesn't apply to the live preview, which scrolls normally since it's a real page.
Which devices can I preview?
A set of common presets — iPhone, Android (Pixel/Galaxy), iPad, and standard laptop/desktop sizes — plus a custom width and height for anything else you need to check.
Does this work on password-protected or localhost pages?
No — it can only load pages your site serves publicly, the same as any visitor without an account. It also can't reach internal/private addresses, including your own machine's localhost, by design.