Free developer tools

These are the tools that are up. Each one opens as a page on this site.

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Units
Convert rem, em, px, and other CSS lengths in the browser.
CSSOpen
California SDI
Estimate 2026 CA SDI withholding at 1.3% with no wage cap.
PayrollOpen
Ireland PRSI
Class A employee PRSI from 1 October 2026 at 4.35%, with the prior 4.2% beside it.
PayrollOpen
South Africa PAYE
Estimate PAYE from SARS 2026/27 brackets and age rebates.
PayrollOpen
Spain Payslip
Worker social-security lines for an indefinite Spanish contract.
PayrollOpen
JavaScript regex tester
Test a JavaScript pattern in the browser. Matches, groups, a plain explanation, and a step-through.
DeveloperOpen
JavaScript regex builder
Build a JavaScript pattern from plain words. Copy the pattern and a sentence of what it matches.
DeveloperOpen
Text case converter
Paste once and see sentence, title, camelCase, snake_case, kebab-case, and more.
DeveloperOpen