Will your page render at desktop width on phones?
Paste your page and we check for the mobile viewport meta tag - the one line that decides whether phones fit your page to the screen or shrink the whole desktop layout down. Free, no signup.
What we check
We check whether the page you submit declares a mobile viewport meta tag - the <meta name=viewport> line that tells a phone to render your page at the screen's width instead of shrinking a full desktop layout down to fit. Without it, mobile browsers fall back to a wide desktop viewport, and your page loads zoomed-out with tiny, unreadable text.
This is a presence check: we confirm the viewport tag is declared in the page's head. We don't grade the tag's settings or fully simulate every phone - a misconfigured viewport is its own thing - but a missing tag is the common, total break, and it's the one we catch.
Why it matters
The viewport tag is one line, and it's either there or it isn't. Most frameworks add it for you, which is exactly why it's easy to lose: a custom HTML template, a stripped-down landing page, a hand-rolled head, and suddenly the tag nobody thinks about is gone. On your desktop everything looks perfect.
Then more than half your visitors show up on phones and get a desktop layout crammed into a 6-inch screen - pinch-to-zoom, microscopic text, buttons too small to tap. They bounce, and you never see it because you built and tested on a laptop. A two-second check tells you whether mobile visitors are getting a page built for their screen or a shrunk-down desktop one.
Questions
What does the viewport tag actually do?
It tells mobile browsers to render your page at the device's width. With it, your layout adapts to the phone screen; without it, the browser assumes a desktop-width page and shrinks the whole thing down, so text and buttons come out tiny.
Is this a full mobile-friendly test?
No. We check one specific, high-impact thing: whether the viewport meta tag is present. A missing tag is the common total break. Full mobile-friendliness also depends on responsive CSS and tap-target sizing, which a tag check doesn't grade - this rules out the single most common cause.
My framework adds this automatically - do I still need to check?
Most do, which is why a missing tag usually means a custom template, a hand-built landing page, or a head that got overwritten. Those are exactly the cases worth a quick check, since the tag is gone without anything obvious telling you.
Is it really free?
Yes. Paste a URL and run it, no account needed. The same scan also runs all of CopyMosaic's other checks, and you can open the full report to see them.