Free tools
Nothing here wants an account.
Each one exists because a specific day of the path needed it and no good version was free. They run entirely in your browser, so the token or prompt you paste in stays on your machine.
8 tools2 explorers10 run on device0 uploads
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The Gap Check
24 graded questions, three from each phase. You get a wrong answer explained either way, a picture of which of the 358 concepts your answers cover, and one number: the day to start on.
Take the check- 24
- questions
- 7
- minutes
- 1
- day, at the end
Tools
Each of these acts on something you bring: your expression, your token, your document, your numbers.
- DAY 68RUNS ON DEVICEToken and cost calculatorWhat does this prompt cost me at a hundred thousand calls a day?Count exact tokens, then price them at any rate and any volume.OpenBefore you ship an LLM feature and someone asks what it costs to run.
- DAY 58RUNS ON DEVICECapacity calculatorHow many servers does a million users actually need?Turn daily users into peak QPS, storage, bandwidth, and servers.OpenThe estimation every system design interview opens with.
- DAY 74RUNS ON DEVICEChunking playgroundWhere exactly does my document get cut?See exactly where your document splits and what each chunk costs.OpenWhen retrieval returns something plausible and wrong.
- DAY 39RUNS ON DEVICEJWT decoderWhat is actually inside this token, and has it expired?Decode any token and read its claims in plain English.OpenWhen auth fails and the token is the only evidence you have.
- DAY 51RUNS ON DEVICECron explainerWhen does this actually run?Read any cron expression in English and see its next five runs.OpenBefore you commit a schedule you are not certain about.
- DAY 53RUNS ON DEVICEAvailability calculatorHow much downtime does that number actually allow?Turn nines into real downtime, and see what happens in series.OpenWhen someone promises four nines and nobody has checked the maths.
- DAY 09RUNS ON DEVICEStack readerWhat did I sign up to own when I installed that?See every concept your own dependencies assume you already understand.OpenWhen you inherited a codebase, or picked packages faster than you learned them.
Explorers
These two take no input. They are things to look at until a shape you had been guessing at becomes obvious, which is a different job from a calculator and it was dishonest to call them the same.
I am doing the ninety days too, in public.
The occasional email when I ship a free tool, or when a day does not survive contact with me.