Password Checker — Test Password Strength
Check how strong your password is with detailed feedback.
Your password is never sent anywhere — analysis runs entirely in your browser.
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developerAbout Password Strength Checker
Password Strength Checker is a single-page tool for the common web and productivity utility task it is named after. Check how strong your password is with detailed feedback. The interface keeps the input on one side, the configurable options in the middle, and the result on the other side. Most jobs start and finish without any scrolling.
Internally the tool runs on the zxcvbn password-strength estimator — the same processing stack used by professional desktop pipelines, just compiled for the browser. 0 MB is the practical ceiling, set so the tool stays responsive on phones and older laptops.
Reach for Password Strength 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.
Because everything runs in the page, the tool scales the same way for one user or a million — there is no per-user backend cost. The page is static, the engine is the same JavaScript bundle for every visitor, and the work happens on the visitor's own device. That keeps the tool free and keeps it fast on the first interaction.
Constraints worth knowing about: inputs are capped at 0 MB to keep memory usage in a sensible range, one input is processed per run, and the tool must be loaded over HTTPS for the in-browser engine to work. These are properties of the architecture.
If your task needs more than one step, chain Password Strength Checker with Password Generator, Hash Generator, and UUID Generator. 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.
Password Strength Checker sees the most use from researchers gathering quick references and community managers planning posts, but the design is intentionally generic enough that you do not need a specialist background to get a good result. The defaults aim at the most common case so a first-time user can get the right output without changing any settings.
Output handling is intentionally boring: Password Strength Checker produces a single output file and triggers your browser's standard "save" behaviour. If you have a default download folder configured, that is where it will land. There is no Favtoo-side history of jobs you have run.
Password Strength 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.
Password Strength Checker is one example of a broader pattern: utility software increasingly works as single-page, client-side experiences. Every page in the catalog is shaped that way, which keeps each tool fast to load and easy to recommend in a single link.
A few practical tips that experienced users of Password Strength Checker pick up over time. First, keep your default browser updated — the engine relies on standard web APIs and newer browser versions are noticeably faster than ones from a few years ago. Second, close other heavy tabs before processing a large input; the engine shares CPU and memory with whatever else is open. Third, if you re-run the same kind of job often, your last-used settings are remembered for the rest of the tab session, so subsequent runs are essentially one click.
Password Strength Checker runs as a regular web page, so there is no install step or permission grant before the first run. The page can be audited by viewing the source or by watching the developer-tools Network tab while a job runs.
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.
If Password Strength Checker solved your problem, sharing the page link with someone who has the same problem is the most useful thing you can do. The catalog grows mostly through word of mouth; visitors arriving through a recommendation tend to be the ones the tool serves best.
How it works
- 1Open Password Strength Checker in your browser. The page loads quickly and the tool is ready to use the moment it becomes interactive.
- 2Drop a web utility file onto the upload area, or click to pick one from your device.
- 3Adjust the options to match what you need. Sensible defaults cover the most common case, so you can usually skip this step.
- 4Click to start the job. The engine (the zxcvbn password-strength estimator) processes the input in the page; you can watch the progress indicator until it completes.
- 5Download the result. The file is generated in your browser and saved through your normal download flow.
- 6Run additional jobs as needed. The same controls and defaults apply on every run.
Common use cases
- Validate a setting before circulating it to a team using Password Strength Checker.
- Run a fast accessibility check before publishing.
- Sanity-check a webhook response while debugging.
- Pull a quick reference number for a status update.
- Create a placeholder image for a wireframe.
- Run a one-off check during a meeting without context-switching.
- Preview how a result looks before deploying it.
- Audit a marketing page before launch.
- Compare two product variations side by side.
- Generate a temporary asset for a social post.
FAQ
How is strength measured?
Using the zxcvbn library that checks for common patterns, dictionary words, and keyboard sequences.
Is my password stored?
No — your password is never sent anywhere. All analysis happens in your browser.
What does the crack time mean?
An estimate of how long it would take to guess your password using common attack methods.
Can I call Password Strength Checker from a script?
Password Strength Checker is a browser-only tool by design and does not expose a hosted API. The reason is the same as the privacy story: there is no Favtoo backend doing the work, so there is no service to call. If you need to script the same transformation, the underlying engine (the zxcvbn password-strength estimator) is open-source and can be used directly from your own code.
How often is Password Strength Checker updated?
Password Strength 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.
Will Password Strength Checker keep working if my Wi-Fi drops mid-task?
Once the page is loaded, Password Strength Checker can complete jobs without an active internet connection — the engine is bundled with the page, so there is no per-job network call. The initial page load does require a connection (to fetch the static assets), but after that you can disconnect entirely and the tool will still work. This is a side-effect of the local-first architecture, not a deliberate "offline mode" feature.
Does Password Strength Checker work in Safari, Firefox, Chrome and Edge?
Password Strength 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 Password Strength Checker?
Password Strength 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.
Will Password Strength Checker ask me to pay to download the result?
Password Strength Checker is free to use. The processing runs in your browser, which keeps the per-user cost low enough that the tool can be offered openly. The download is the same file the engine produced — you can use it for as many runs as you need.
Is Password Strength Checker licensed for business use?
Password Strength Checker can be used for personal and commercial work alike — there is no separate "business" licence to purchase. The output you generate is yours to use however you want, including in client deliverables, internal documents, or commercial products. Favtoo's only ask is fair, individual use; the tool is not designed to be embedded as a backend service or wrapped behind an API for resale.