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Concurrency

Compare any two currencies. On the fly.

Compare currencies with a slide of your finger. Real rates, no accounts, works offline the moment you land.

Concurrency app screenshot

Built for the moment you land.

Small, fast, honest. Everything a converter should be — nothing it shouldn't.

Traveler-first

Built for the moment you're at a foreign ATM.

Offline-ready

All 154 currencies keep converting without a signal, using the last rates you downloaded.

Real rates

Daily-refreshed European Central Bank rates via Frankfurter, with ExchangeRate-API as backup. Tap the footer to refresh manually.

Slide or type

Slide the amount to feel it. Tap for the keypad.

No account

No sign-up. No tracking. All data stays on your device.

Install the web app

Add it to your home screen and it opens full screen, no browser chrome.

New · Editorial redesign

A new visual language.

Print-inspired typography, hairline rules, a two-slab paper & ink layout, and a new gold app icon. Same real rates. Same instant install.

Launch — new gold icon
Launch — new gold icon
Exchange
Exchange
Currency picker
Currency picker
Amount keypad
Amount keypad
Settings
Settings

Three taps. One number.

No menus to learn. No settings to fuss over. Just the answer.

1

Pick two currencies

Choose the pair you're comparing. Favorites and recents are always at the top.

2

Enter the amount

Slide to feel it, or tap for the keypad. Whichever way your thumb lands.

3

See the answer

A single, locale-formatted number. Real rate. No mental math.

Wherever you are.

Ship first on the web. Native apps later — same interface, same feel.

LIVE

Web

https://concurrency.rabid.co · Install as a PWA

COMING SOON

iOS

TestFlight beta later this year.

COMING SOON

Android

Play Store beta later this year.

Nothing leaves your phone.

Rates come in. Nothing about you goes out. Your device stays your device.

No account
No tracking
No cloud sync
Data stays local