Base64 Encoder
Convert plain text to Base64 format instantly with Unicode support
29 browser-based tools
Toolk converters transform structured data, measurements, dates, encodings, and files without sending the input to a conversion server. Use directional pages for precise tasks such as CSV to JSON, JSON to CSV, PX to REM, or REM to PX. Each page documents its parsing rules, rounding behavior, supported formats, and the edge cases most likely to change the result.
Tool inputs stay on your device. Page-view analytics never include tool input.
Featured starting points appear first, followed by the complete category in alphabetical order. Every card links to one canonical tool page with its own working interface, examples, limitations, sources, and related utilities.
Convert plain text to Base64 format instantly with Unicode support
Convert CSV to a clean JSON array of objects. Handles quoted fields, custom delimiters, headers, and optional type inference. Runs 100% in-browser.
Generate QR codes for URLs, text, and more
Convert between Unix timestamps and human-readable dates
Encode and decode URLs for web development
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
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
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.
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
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
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
This category groups tools by the job they complete, not by a search-keyword variation. Choose the smallest utility that matches the input and output you need.
These guides explain the standards, formulas, and failure cases behind the working tools. Use them when the conversion result needs more context than a one-line output.
Web Development
Convert CSV to JSON without corrupting data: how to handle quoting, delimiters, type inference, and nesting, plus a worked round-trip showing what survives.
Read guideSecurity
Learn how Base64 converts bytes to text, why it adds about 33% overhead, when URL-safe encoding matters, and why Base64 provides no encryption or secrecy.
Read guideWeb Development
A Unix timestamp counts seconds since 1970-01-01T00:00:00 UTC, ignoring leap seconds. Learn seconds vs milliseconds, the Year 2038 problem, and conversion.
Read guideEach direction has different inputs, output rules, examples, and failure cases. Separate pages make the intended transformation clear and avoid hiding behavior behind a query parameter or mode switch.
Each converter documents its own formula and rounding behavior. Exact integer tools use BigInt where needed, while measurement and finance tools state their precision and limitations beside the result.
No. File-based converters use browser APIs such as FileReader and Canvas. The selected file stays in the active browser tab unless a tool page explicitly states a different network behavior.
Last updated: . Category membership and tool counts come directly from the current Toolk catalogue.
Browse all 90 browser-based tools (90 currently marked free), or tell us what useful utility we should build next.