OTP Generator — One-Time Password Codes
Generate cryptographically random one-time passwords (OTP) with configurable digit length for testing and prototyping.
How it works
- 1Configure your options above
- 2Click "Generate OTP" — processing happens in your browser
- 3Copy or download the result
What to do next
About OTP Generator
OTP Generator performs otp generator as a focused single-page utility. Generate cryptographically random one-time passwords (OTP) with configurable digit length for testing and prototyping. Defaults are tuned for the common case so the first run is one click, with every option that matters exposed for the moments you need to fine-tune the result.
Internally the tool runs on standard browser APIs — 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.
The right moment to reach for OTP Generator is when you have a focused developer utility job that fits inside a browser tab. Open the page, drop in the file or paste your input, choose the options that matter, and the tool returns the result.
The browser sandbox isolates the page's JavaScript from the rest of the system, the same way it isolates every other tab you have open. OTP Generator works inside that sandbox: it reads the file you give it, processes it with standard browser APIs, and writes the result back. Nothing leaves the page's memory unless you choose to download or copy it.
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.
Even on its own, OTP Generator composes well with the rest of your toolkit. The output is a standard developer file that opens in any program that handles the format, so the result of one run can become the input to whatever step you use next.
OTP Generator sees the most use from students learning new languages and frontend developers prepping fixtures, 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: OTP Generator 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.
OTP Generator 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.
OTP Generator is structured around the idea that a useful tool should be its own page. Open the page, do the work, close the tab — the page is the entire product. There is no onboarding flow because there is nothing to onboard into.
Useful patterns when working with OTP Generator: keep the input file open in another tab so you can compare against the result; give the output file a descriptive name when saving so you can find it later (the default name is sensible but generic); and treat each run as independent — the tool has no concept of "history", which means you cannot accidentally pollute one job with leftovers from another.
OTP Generator 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 OTP Generator appears to hang, the engine is almost certainly still working — large inputs simply take longer to process inside a browser than they would on a server with multi-core scheduling. For inputs near the 0 MB cap, give it up to a minute on a typical laptop before assuming something is stuck.
That is the whole tool. Use OTP Generator for as long as it stays useful to you, and if it does, the catalog has many more tools built the same way. Each applies the same single-purpose discipline, so the way you used this page transfers to the next one you try.
How it works
- 1Open OTP Generator in your browser. The page loads quickly and the tool is ready to use the moment it becomes interactive.
- 2Select the developer file you want to process — drag-and-drop and the file picker both work.
- 3Adjust the options to match what you need. Sensible defaults cover the most common case, so you can usually skip this step.
- 4Hit the run button. standard browser APIs does the work in your browser tab.
- 5Save the output when it is ready.
- 6Re-run with different settings as often as you want. Each run produces a fresh output and the original file on disk is never modified.
Common use cases
- Hash a string for a quick reproducibility check using OTP Generator.
- Format a noisy log line into something a teammate can read.
- Validate a config blob before pushing to staging.
- Pretty-print a minified blob during incident triage.
- Generate boilerplate from a single specification line.
- Compare two API responses to spot a regression.
- Inspect a payload during local development without writing a script.
- Inspect a regex against a test string before committing it.
FAQ
Are these real OTPs?
These are random numeric codes suitable for testing and prototyping. Real OTP systems use time-based (TOTP) or counter-based (HOTP) algorithms with shared secrets.
What length should I use?
6 digits is the most common for SMS and authenticator apps. 4 digits is used for simpler verification. 8 digits provides extra security.
Are the codes secure?
Yes — the tool uses crypto.getRandomValues for uniform random generation, avoiding modulo bias.
Can I use these in production?
These random codes work for testing. Production OTPs should use TOTP/HOTP algorithms (RFC 6238/4226) tied to user secrets.
Is anything stored?
No — codes are generated in your browser and never sent anywhere.
Can I generate multiple OTPs?
Yes — set the count to generate up to 50 OTPs at once.
Does OTP Generator need an internet connection to run?
Once the page is loaded, OTP Generator 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.
Can OTP Generator run inside a corporate firewall?
OTP Generator 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.
Will OTP Generator ask me to pay to download the result?
OTP Generator 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.
How often is OTP Generator updated?
OTP Generator 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.
Do I need a specific browser to use OTP Generator?
OTP Generator 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.
Does OTP Generator support batch processing?
OTP Generator 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.
Can I use OTP Generator for commercial work?
OTP Generator 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.
How accessible is the OTP Generator interface?
OTP Generator 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.