Format currency for any locale
Lean on Intl.NumberFormat to render numbers as currency, decimal, or percent — for any of 18 locales and 20 currencies. All in-browser.
How currency formatting works
Intl.NumberFormat resolves locale, currency, and notation into the right grouping, symbol, and digits — no manual rules needed.
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Type a number
Any numeric value, positive or negative.
Inputs are treated as UTF-8 throughout the pipeline and validated client-side as you type — nothing dispatches until the value is well-formed.
inpututf-8client-sidevalidatedn · text1234567.89 · set1234567.89
loaded · parsedclient-side - 02
Choose locale
Locales pick grouping, decimal mark, currency placement.
Each toggle re-computes through a memoised hook, so flipping options never resets your input and the UI stays snappy on large inputs.
localeoptionslivememoisedtogglesloc · memoisedde-DE · live1.234.567,89 €
options set · memoisedlive - 03
Pick style
currency, decimal, percent.
Randomness — where used — comes from
crypto.getRandomValues, neverMath.random. Heavy work sits inuseMemo.stylecomputeinstantlocaldeterministicstyle · instantcurrency · computed$1,234,567.89
computed · instantinstant - 04
Set notation & digits
compact gives 1.2M, scientific 1.23E6.
Copy writes through
navigator.clipboardand downloads use aBlob— zero network traffic. Same input plus same options always yield the same bytes.notationcopydownloadzero-networkreproducibleok · copiedready · copied$1.2M
shipped · ready to shipsuccess
Pro tips for everyday utilities
Reach for crypto.getRandomValues
Cryptographically random for IDs, tokens, salts. Math.random is for animation and games, not security.
Mock data with seeds
Faker-style libraries can be seeded so tests are reproducible. Embed the seed in the fixture file.
Reference cards beat memory
Cheatsheets for Vim, Git, Docker, Linux signals are faster than man pages when you’re mid-flow.
Browser APIs vary
Touch events, gamepads, and clipboard differ across vendors. Feature-detect before use.
Persist in the right place
localStorage for user preferences, sessionStorage for transient state, IndexedDB for structured data.
When you need locale-aware formatting
Invoices, dashboards, i18n, receipts.
Invoices
Currency symbol exactly where the locale expects. Random values come from crypto.getRandomValues — cryptographically secure for tokens, salts, and session IDs. Math.random is deterministic enough for animations but predictable enough to be a security bug.
CSPRNG-backedDashboards
Compact notation keeps cards tidy (1.2M, 4.5K). Pair with hashids, ULID, or UUID v7 when you need both random and sortable — useful for primary keys, public-facing IDs, and event log ordering without a sequence column.
reproduciblei18n
Same number, eighteen different formats. Output is deterministic given the same seed, so fixtures and tests stay reproducible across CI runs and contributor machines. Embed the seed in the fixture file for full replay.
snappyReceipts
Two decimals for USD, none for JPY. Heavy work runs through useMemo so the UI stays snappy on large inputs. Same input + same options yields identical bytes — the kind of stability snapshot tests rely on.
feature-detectedForecasts
Scientific notation for very large numbers. Storage tools persist to the right backend: localStorage for user preferences, sessionStorage for transient state, IndexedDB for structured data. Pick the right shelf and quota worries disappear.
deterministicCross-region apps
Render the same value correctly for every user. Browser feature detection: clipboard, fullscreen, gamepad, and Web Bluetooth APIs gracefully fall back when unavailable. No surprise white screens on Safari or older Firefox.
production-readyFrequently asked questions
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