Free tools for builders
7 toolsSmall, focused utilities that calculate, inspect, convert and generate. They run in your browser, need no account, and explain how they work.
JWT Inspector
Decode a JSON Web Token's header and payload and check its time claims.
Cron Expression Builder
Build a cron schedule and read it back in plain English with the next run times.
JSON to TypeScript Converter
Turn a JSON sample into TypeScript types you can paste into a project.
Prompt Formatter
Structure a prompt into clear, labeled sections or tidy an existing one.
LLM API Cost Calculator
Estimate what an LLM-powered feature will cost per request, day, month and year.
Token Calculator
Count the tokens in a piece of text and see how much of a context window it uses.
SaaS Pricing Calculator
Model your own SaaS plan: revenue, fees, costs, margin and break-even.
Runs in your browser
Your input isn't sent to our servers.
Shows its method
Each tool explains its formula or rules, its assumptions and its limits.
Dated where it matters
Tools that rely on prices or model data show when that data was last checked and where it came from.