Every tool you need for the daily work
Calculators, converters, developer utilities, and text tools — all running locally in your browser. Fast, private, and free.
Popular tools
View all →JSON to TypeScript
Generate TypeScript interfaces and types from any sample JSON. Handles nested objects, arrays, optional fields, and mixed types. Paste JSON, copy the interface.
Token Counter for GPT, Claude, Llama
Count tokens for ChatGPT, GPT-4o, Claude, Llama, and Gemini before hitting context limits. Shows per-model token count, character count, and approximate API cost.
Regex Tester
Test JavaScript regular expressions live with instant match highlighting. Supports all JS regex flags (g, i, m, s, u) and shows match groups, indices, and global matches.
URL Encoder/Decoder
Percent-encode and decode URLs and query string values. Handles full URLs or individual components — paste any URL to encode special characters or decode percent-encoded strings.
Text Diff
Side-by-side diff comparison of two text blocks with line-by-line highlighting. Shows added, removed, and changed lines — useful for comparing document versions or config files.
List Set Operations
Perform set operations on two lists: union, intersection, difference, A-only, B-only, and symmetric difference. Paste two lists and choose the operation — results update instantly.
Days Between Dates — How Many Days Calculator
Find how many days are between two dates — plus weeks, months, and years. Counts calendar days inclusive or exclusive. Free, runs in your browser, no signup.
Percentage Calculator
Calculate what percent of a number is, find percent change, and reverse-calculate any percentage. Three modes — pick the one that matches your problem, get the answer instantly.
Browse by category
Developer Tools
Tools every web developer needs.
Text & String
Manipulate, count, compare, and clean text.
List Tools
Set operations, filtering, and clipboard transforms for lists.
Date & Time
Date math, age, and timezone tools.
Math
Calculators for everyday and advanced math.
Unit Converters
Convert between units of length, weight, temperature, and more.
Number & Code
Binary, hex, ASCII, and base converters.
Generators
Passwords, IDs, QR codes, and more.
Design & CSS
Color, typography, spacing, and CSS generators.
Network & Security
Networking, certificates, hashing, and security utilities.
Personal Finance
Loans, taxes, salary, and everyday money decisions.
Investing & Corporate Finance
Valuation, options, fixed income, and risk metrics for analysts.
Marketing & SEO
Ad math, conversion, A/B testing, and SEO helpers.
PDF Tools
Merge, split, convert, and edit PDF files — all in your browser.
Electrical & Electronics
Practical calculators for circuits and electronics.