Viewport Size Checker — JS Snippet
Generate a JavaScript snippet to detect viewport dimensions, scroll position, and Tailwind CSS breakpoint.
How it works
- 1Configure your options above
- 2Click "Generate Detection Script" — processing happens in your browser
- 3Copy or download the result
What to do next
About Viewport Size Checker
Viewport Size Checker handles a focused step in the modern web and productivity utility workflow. Generate a JavaScript snippet to detect viewport dimensions, scroll position, and Tailwind CSS breakpoint. The page loads with the upload area, controls and result panel all visible at once, so the path from "I have a file" to "I have the result" is one screen long.
From a technical standpoint, Viewport Size Checker is JavaScript and standard browser APIs running in your tab. The browser is the runtime; the page is the interface. Maximum input size: 0 MB per run.
Viewport Size Checker parses your file with standard browser APIs entirely inside the browser, applies the options you selected, and returns a download. The processing has no network step, which means a slow or intermittent connection does not slow down the work — once the page is loaded, only your CPU and RAM are involved.
The heaviest users of Viewport Size Checker tend to be marketers running campaigns, creators experimenting with formats and analysts pulling lightweight reports. Each group brings slightly different expectations to the tool, but the same single-page architecture serves every one of them with the same response time.
Reach for Viewport Size Checker when you need a predictable result on a single file. The page works on the first visit, the controls are visible without a menu, and the output is delivered the moment the engine finishes.
The only practical limit is the 0 MB per-file ceiling, which keeps the tool responsive across a wide range of devices. Run the tool ten times in a row, run it ten thousand times — it behaves the same way and produces the same quality of result.
If your task needs more than one step, chain Viewport Size Checker with Screen Resolution Checker, Device Pixel Ratio Checker, and Browser Info Detector. Each tool produces output that is a clean input to the next, so multi-step workflows are just a matter of opening the next tool in a new tab and continuing.
Viewport Size Checker keeps the control set focused. Every option on the page is there because a real workflow needs it, and the defaults aim at the most common case so a first-time user can get the right output without changing any settings.
Viewport Size Checker returns the result as a download. If you are running multiple jobs, the output names will not collide as long as the input names differ. You can re-run with different settings as many times as you like; each run produces a fresh file with no caching trickery in between.
Some background on the design choices behind Viewport Size Checker: every option you see on the page is there because a real workflow needs it, and every option that is not shown has been deliberately omitted to keep the common case fast. The bias is toward minimal-but-complete.
As a single-page tool, Viewport Size Checker stays focused on one web and productivity utility step. Multi-step workflows are composed by chaining adjacent tools — each tool produces a standard file the next one can read directly, so a longer pipeline is just a sequence of short tab-and-tab visits.
If you want to get the most out of Viewport Size Checker, three small habits help. Drag-and-drop is faster than the file picker once you get used to it. The keyboard shortcut for downloading the result is whatever your browser uses for "save link as," because the result is a normal download. And if you are working on a sensitive file, processing in an Incognito or Private window is a good extra layer — it leaves no trace in browser history when the tab closes.
If the result is not what you expected, the most common causes are easy to check. Confirm the input is under the 0 MB ceiling — files just above the cap fail silently because the engine refuses to allocate the buffer. Confirm the input is one of the supported formats. And if the page itself feels slow, try closing other heavy tabs to free up memory; the engine runs in your browser, so it competes for the same resources as everything else open.
Viewport Size Checker is intentionally narrow in scope so the common case is fast and the result is predictable. If you ever need a variation it does not cover, browse the rest of the catalog — there is a good chance an adjacent tool already exists, and switching between tools is just a matter of opening another tab.
How it works
- 1Open the Viewport Size Checker workspace above. The interface is a single page, so there is nothing to navigate.
- 2Add your web utility input by dropping it onto the page or browsing for it.
- 3Tweak the controls if the defaults are not quite right for your input. The options are kept short and labelled in plain language.
- 4Click to start the job. The engine (standard browser APIs) processes the input in the page; you can watch the progress indicator until it completes.
- 5Grab the output as soon as the run completes. You can also copy the result instead of downloading if the next tool in your workflow accepts pasted input.
- 6Run additional jobs as needed. The same controls and defaults apply on every run.
Common use cases
- Compare two product variations side by side using Viewport Size Checker.
- Generate a temporary asset for a social post.
- Pull a quick reference number for a status update.
- Audit a marketing page before launch.
- Create a placeholder image for a wireframe.
- Generate a campaign asset in seconds for a quick test.
- Plan content without paying for a SaaS dashboard.
- Run a one-off check during a meeting without context-switching.
FAQ
Viewport vs screen?
Viewport is the visible content area inside the browser window; screen is the full display resolution.
What is detected?
Inner width/height, document dimensions, scroll width/height, scroll position, and outer dimensions.
Tailwind breakpoints?
The script maps the viewport width to Tailwind CSS breakpoints (sm, md, lg, xl, 2xl).
Private?
Yes — runs locally.
Dynamic updates?
The script captures a snapshot. For real-time monitoring, add a resize event listener.
Mobile considerations?
Mobile browsers may report different viewport sizes due to toolbar visibility changes.
Is there a desktop version of Viewport Size Checker?
No installation is needed. Viewport Size Checker runs as a normal web page, with no browser extension, no native helper, and no separate desktop client to download. That is partly a privacy choice — extensions can request broad permissions, while a regular page is sandboxed by default — and partly a convenience one: you can use Viewport Size Checker on any computer you have temporary access to without leaving anything installed on it.
Are there any usage limits on Viewport Size Checker?
Inputs are capped at 0 MB per file, which keeps memory usage stable across phones, tablets and older laptops. You can run Viewport Size Checker as often as you need; every run produces a full-quality result.
Will Viewport Size Checker keep working in a year?
Viewport Size Checker is updated whenever the underlying engine releases an improvement or a bug fix. Because the tool is delivered as a static page, every visit fetches the latest version automatically — there is no "version" to manage on your end. If a particular release ever changes default behaviour, the change is documented on Favtoo's changelog so you can confirm what shifted.
Does Viewport Size Checker work in Safari, Firefox, Chrome and Edge?
Viewport Size Checker works in any modern browser released in the last few years — Chrome, Edge, Firefox, Safari, Brave, Arc and the major Chromium derivatives are all supported. The underlying engine relies on widely-supported web APIs, so there is nothing exotic to install. If you are on a very old browser version and the tool fails to load, updating to the latest release of your preferred browser is the only fix needed.
Can I process multiple files at once with Viewport Size Checker?
Viewport Size Checker processes one input at a time by design — it keeps memory usage predictable on lower-end devices and makes results easier to verify. To handle a folder, run the tool once per file; the page stays loaded between runs and remembers your last-used settings, so the second run is essentially instant.
How long does Favtoo retain my data after using Viewport Size Checker?
Favtoo keeps no copy of your file because Favtoo never receives your file. Viewport Size Checker runs entirely in your browser, the input is held only in your tab's memory, and closing the tab discards it. There is no opt-in cloud history, no "recent jobs" panel synced to an account, and no server-side retention to configure — the architecture simply has nowhere for your file to be stored.
Does Viewport Size Checker upload my file to a server?
Your file is processed inside your browser by standard browser APIs. The engine reads the file's bytes from your tab's memory, computes the result, and writes the result back into the tab. You can confirm what the page does by opening developer tools and watching the Network tab during a run — the requests you see are for the tool's static assets only.
How accessible is the Viewport Size Checker interface?
Viewport Size Checker uses native HTML controls wherever possible, which means keyboard navigation, focus rings, and screen-reader labels work the way the platform expects. The drop zone accepts files via the keyboard-accessible file picker as well as drag-and-drop, and result downloads use standard browser download flows. If you spot an accessibility gap, Favtoo treats it as a bug worth fixing.
Is the source for Viewport Size Checker available?
Viewport Size Checker is a static page running an open-source engine in your browser, so a typical corporate firewall does not get in the way as long as it allows JavaScript to load from Favtoo. For teams that need to host it themselves on an internal network, the underlying engine (standard browser APIs) is open-source and can be packaged into a private build with the same behaviour. Reach out via the Contact page if that is something you are exploring.