- Web app
- Tools
- SEO
A library of 144 client-side web tools and calculators
A static, search-friendly site of finance, developer, health and business tools that run entirely in the browser, built from one reusable pattern.
- Industry
- Utilities / online calculators
- Our role
- Design, development and release
- Stack
- ReactTypeScriptViteTailwind CSSRadix UIVitestPWA
The challenge
Online calculators and converters are searched for constantly, but most are slow, ad-heavy or send your numbers to a server. The goal was a large, fast library of tools that could be added one at a time without the codebase turning into a pile of one-off pages.
Screenshots
Screenshots show demo data.
What we built
One pattern for every tool
Each tool is three pieces: a pure calculation function, a UI, and a registry entry. Adding a tool follows the same steps every time.
144 tools in 13 categories
Finance is the largest group at 42 tools, followed by developer, health, business and text tools.
Runs in the browser
Almost every tool works fully on the device, with no backend, and works offline as an installable web app. Only a few tools, such as ones that look up live data, use the network.
SEO built from the registry
Titles, descriptions, FAQs and structured data are generated from each tool's registry entry, and pages are pre-rendered as static HTML.
Switchable tools
A flag file turns individual tools on or off, so unfinished or unverified tools never ship.
Engineering decisions
- Calculation logic lives in pure functions with their own unit tests, separate from the interface, so figures can be checked without a browser.
- Static site generation instead of a server, so pages load fast, cost almost nothing to host and are easy for search engines to read.
- A single registry as the source of truth for navigation, search, SEO and structured data, so a new tool needs no changes elsewhere.
- Finance and tax tools were reviewed for accuracy before being enabled, because wrong numbers cost users money.
The result
A fast, installable library of 144 tools that can grow one tool at a time, with no server to run and users' inputs staying on their own device.
Built by our lead developer as our own product.