The tools run entirely in your browser. Inputs are not uploaded, logged or stored because there is no backend to receive them.
They are free, require no account and work offline after the page loads. Calculator pages state the assumptions that affect their results.
Most used
Cloud Cost Calculator
Compare estimated monthly AWS, Azure and Google Cloud costs for compute, storage, outbound transfer, managed databases and load balancing.
Personal financeMortgage Payoff Calculator
Estimate how extra monthly, annual or lump-sum principal payments change mortgage interest and payoff time.
Developer toolJWT Decoder
Decode a JSON Web Token in your browser to inspect its header, payload, registered claims and expiry time.
Developer toolJSON Formatter and Validator
Format, validate, minify and sort JSON in your browser. Syntax errors include the line, column and nearby text.
Developer toolRegex Tester
Test JavaScript regular expressions in your browser. Highlight matches, inspect capture groups and load common pattern examples.
Everything else
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SaaS Seat Cost Calculator
Project per-seat software costs as headcount and prices change, then compare monthly and annual billing over one to ten years.
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Cron Expression Generator
Build or parse a standard five-field cron expression, read its schedule and calculate the next ten runs in local time.
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Color Contrast Checker
Check a foreground and background color against WCAG 2.2 AA and AAA contrast thresholds, with a preview and an adjusted foreground option.
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Base64 Encoder and Decoder
Encode UTF-8 text as Base64 or Base64url, or decode it locally in your browser. Emoji and accented characters are supported.
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UUID Generator
Generate UUID v4 or time-ordered UUID v7 values with the browser Web Crypto API, in batches of up to 1,000 and several output formats.