All Free Online Developer Tools & Utilities

Calendar-accurate age between any two dates — years, months, days plus total weeks, hours, seconds, and next-birthday countdown

Decode Base64 strings back to readable plain text safely

Convert plain text to Base64 format instantly with Unicode support

Decode Base64 strings back to downloadable image files

Body Mass Index with metric or imperial units, WHO categories, and healthy weight range for your height

Estimate body fat percentage from tape-measure values (neck, waist, hip, height) using the US Navy circumference method with ACE body-fat category lookup, lean and fat mass output, and metric or imperial units

Mifflin-St Jeor BMR + TDEE with five activity levels and per-goal daily calorie targets for maintenance, fat loss, and muscle gain

Future value of any savings or investment account with regular contributions and seven compounding frequencies

Bidirectional CSV ↔ JSON converter with RFC 4180 quoting, custom delimiters, and smart type inference

Convert CSV to a clean JSON array of objects. Handles quoted fields, custom delimiters, headers, and optional type inference. Runs 100% in-browser.

Exact difference between two dates in days, weeks, calendar Y/M/D, business days, hours, and minutes — plus a date-arithmetic mode for adding or subtracting years/months/weeks/days from a base date

Weighted and unweighted GPA across the 4.0 and 5.0 scales with full letter grades, P/NP/W exclusion, and per-course contribution breakdown

Bidirectional HTML entity encoder and decoder with four modes, decimal/hex numeric output, and full surrogate-pair Unicode support

Convert images to Base64 encoded strings (Data URI) instantly

Convert a JSON array of objects to CSV instantly. Flatten nested keys, choose a delimiter, and get RFC 4180-quoted output. 100% in your browser.

Auto, personal, student, and credit-card payoff loan calculator with side-by-side term-length comparison, monthly payment, total interest, and full month-by-month amortization schedule

Fixed-rate mortgage calculator with monthly payment, total interest, year-by-year schedule, and extra-payment savings comparison

Five percentage operations in one tool — X% of Y, X as % of Y, percent change, add/subtract a percent — with formula breakdown

Classic 25-minute focus and 5-minute break Pomodoro timer with long-break-every-fourth-session cycle, four built-in presets (Classic, Short Focus, Deep Work 90/20, 52/17), browser notifications, and configurable durations

Convert pixels to rem units instantly with a custom base font size, plus a px-to-rem reference table for responsive, accessible CSS.

Generate QR codes for URLs, text, and more

Convert rem units to pixels instantly with a custom root font size, plus a rem-to-px reference table for precise, predictable CSS sizing.

Encode SVG markup to a Base64 or URL-encoded data URI with a ready CSS snippet, and see which is smaller. Free, client-side, no uploads.

Convert any time between IANA timezones with a live world-clock board showing nine cities at once. DST-aware offsets, 12/24-hour toggle, ISO 8601 output, and full IANA timezone database

Convert between Unix timestamps and human-readable dates

Calculate tip and split the bill across any party size — pre-tax or post-tax mode, optional round-up, per-person breakdown

Universal unit converter across seven categories — length, weight, volume, temperature, area, speed, time — with NIST-exact factors

Encode and decode URLs for web development

Daily water requirement by body weight, activity level, and climate with output in liters, fluid ounces, cups, and 500 ml bottles plus a recommended hourly drinking schedule