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Free online calculators and unit converters for finance, health, math, science, home improvement and…
Fast, private developer utilities — JSON, encoding, hashing, color, CSS, generators, formatters and …
Text tools for writers, students and social media — case converters, font and Unicode generators, co…
Edit, convert and generate images and PDFs right in your browser. Resize, compress, convert formats,…
Handy little browser apps — generators, trackers, planners, timers and references that solve an ever…
Free, private AI utilities — prompt builders and testers, token & cost calculators, model comparison…
Learn AI from zero — clear explainers, a full glossary, step-by-step tutorials, roadmaps, model comp…
Free, private validators and format checkers — VAT and tax IDs, IBAN and bank codes, national identi…
Free tax, payroll and take-home calculators by country and region — income tax, VAT/GST, payroll and…
Featured tools
Hand-picked highlights from each category — open a category hub for its full collection.
Percentage Calculator
Handles every form of percentage question — X% of Y, percent change, difference and reverse percentages — and shows the working.
Calculators & ConvertersCompound Interest & Savings Calculator
Projects savings growth with regular deposits and compounding, so you can see what a habit is worth over years.
Developer ToolsJSON Formatter & Validator
Pretty-print, minify and validate JSON — the everyday workhorse, safe for production payloads because nothing is uploaded.
Developer ToolsRegex Tester with Plain-English Explainer
Live regex matching with a plain-English explanation of what your pattern actually does.
Text & Writing ToolsWord & Character Counter
Instant word, character, sentence and reading-time counts, updated as you type.
Text & Writing ToolsSocial Media Character Counter
Live character count checked against every major social platform's limit at once.
Image & PDF ToolsImage Compressor
Shrinks JPG, PNG and WebP files with a quality slider — without uploading them anywhere.
Image & PDF ToolsHEIC to JPG / PNG / WebP Converter
Converts iPhone HEIC photos to JPG, PNG or WebP locally — the most common 'why won't this photo open' fix.
Everyday & Quick-Help AppsPomodoro Timer
25/5 focus cycles with automatic breaks and a session counter.
Everyday & Quick-Help AppsHabit Tracker
Streaks on a weekly and monthly grid, saved privately in your browser.
AI ToolsToken Counter (Multi-model)
Token estimates for GPT-4, Claude, Llama and Mistral, computed entirely client-side.
AI ToolsLLM API Cost Calculator
The cost of any GPT, Claude or Gemini API call — per request and per month.
Learn AIHow to Build a Chatbot with the OpenAI API
Step-by-step: connect to GPT-4, handle context and deploy a working chatbot in 30 minutes.
Learn AIWhat Is BERT? Google's Bidirectional Transformer Explained
Masked language modelling and the encoder model that dominated NLP before GPT.
Validators & CheckersIBAN Validator
Checks any IBAN with the ISO 13616 mod-97 algorithm — catches typos before a payment bounces.
Validators & CheckersEU VAT Number Validator
Format checks covering all 27 EU member-state VAT patterns in one tool.
Tax & PayrollTake-Home Pay & Salary Tax Calculator
Net salary after income tax and social contributions — covers the UK, US and Germany.
Tax & PayrollVAT & Sales Tax Calculator
Add or remove VAT, GST or sales tax for any country.