Online tools that just work.
Free, no signup, no ads in your face. Everything runs in your browser when it can.
CalculatorsConvertersText & writingDesignProgrammingGenerators
Popular tools
Word Counter
Count words, characters, sentences and reading time.
Character Counter
Count characters with and without spaces, in real time.
Case Converter
Convert text to UPPER, lower, Title, camelCase, snake_case, kebab-case and more.
Slug Generator
Turn any title into a clean, URL-safe slug.
Lorem Ipsum Generator
Generate placeholder text by paragraphs, sentences or words.
Password Generator
Generate strong, random passwords right in your browser.
QR Code Generator
Create QR codes for URLs, Wi-Fi, contacts and plain text.
JSON Formatter & Validator
Format, minify and validate JSON instantly.
Calculators19
Age Calculator
Your exact age in years, months, days and live seconds - plus zodiac and next birthday.
BMI Calculator
Calculate your Body Mass Index in metric or imperial units.
Loan & Mortgage Calculator
Estimate monthly payments, total interest and amortization.
Tip Calculator
Calculate the tip and split the bill between any number of people.
Mortgage vs Rent Calculator
Find your buy-vs-rent break-even point in months.
Income Tax Estimator (US Federal)
Estimate your US federal income tax with progressive brackets.
Salary After Tax Calculator
Net annual, monthly and weekly take-home pay across 5 countries.
Percentage Calculator
Five percent modes in one tool: X% of Y, percent change, reverse percentage, plus add or subtract a percent.
Date Calculator
Days between dates, add or subtract years/months/days, business-day count.
Compound Interest Calculator
Project savings growth with a chart, any currency and inflation-adjusted value.
Discount Calculator
Compute sale price, savings and effective discount.
GPA Calculator
Compute your GPA on the US 4.0 scale, weighted by credits.
TDEE Calculator
Daily calorie needs using Mifflin-St Jeor BMR and activity multiplier.
Recipe Scaler
Scale a recipe up or down by servings or a multiplier.
Microwave Time Converter
Recipe written for an 800 W microwave but yours is 700 W? Get the right cooking time in one tap.
Rule of Three Calculator
Solve a proportion: if A is to B, then C is to ? - leave any box empty and we'll fill it in.
Time Duration Calculator
How many hours, minutes or seconds between two times - or two full datetimes - in your browser.
Pace Calculator
Running pace, distance and time - any two, get the third. Splits in km and miles.
Hourly to Salary Calculator
Convert between hourly wage, weekly, monthly and annual salary - configurable hours/week.
Converters10
Unit Converter
Convert length, weight, temperature, volume and more.
Timezone Converter
Convert a time between any two IANA timezones.
Currency Converter
Convert between 46 currencies at mid-market rates, see a multi-currency table at a glance, and check your bank's spread.
Number Base Converter
Convert numbers between binary, octal, decimal and hexadecimal.
Roman Numeral Converter
Convert decimal numbers to Roman numerals and back.
Oven Temperature Converter
Convert between Celsius, Fahrenheit and UK gas marks.
Unix Timestamp Converter
Convert between Unix epoch (seconds or milliseconds) and human-readable date / time, in UTC and local.
Morse Code Translator
Encode and decode Morse code with audio playback - in your browser, no upload.
Crypto Converter
Convert Bitcoin, Ethereum, 18 more coins, satoshis and 10 fiat currencies - with live prices.
Weather Forecast
Search any city for current conditions, an hourly view for today, and a 7-day forecast - free, no signup.
Text & writing9
Word Counter
Count words, characters, sentences and reading time.
Character Counter
Count characters with and without spaces, in real time.
Case Converter
Convert text to UPPER, lower, Title, camelCase, snake_case, kebab-case and more.
Slug Generator
Turn any title into a clean, URL-safe slug.
Text Diff
Compare two texts line by line or word by word, with a similarity score.
Word Frequency Counter
Count how often each word appears, with stop-word filter.
Remove Duplicate Lines
Strip duplicate lines or words from any list - case-sensitive or not, order preserved or sorted.
Sort Lines
Sort any list A-Z, Z-A, by length, reverse or shuffle - dedupe and trim as you go.
Find and Replace
Find and replace text - one rule or many, plain or regex, with a live match count.
Design18
Color Converter (HEX, RGB, HSL)
Convert colors between HEX, RGB, HSL, HSV, CMYK and OKLCH.
CSS Gradient Generator
Linear, radial and conic CSS gradients with a live preview, presets and one-click copy.
CSS Box-Shadow Generator
Layer multiple CSS box-shadows with live preview, presets and a copy-ready declaration.
Favicon Generator
Drop a square image, download PNG favicons in every standard size.
Contrast Checker
WCAG colour-contrast checker with live ratio, AA/AAA pass-fail badges and sample text.
Color Palette Generator
Generate complementary, analogous, triadic, tetradic and monochromatic palettes from any base colour.
Color Shade Generator
Generate 10 shades and 10 tints of any colour - ready as a hex list or CSS variables.
CSS Clip-Path Generator
Build polygon clip-paths visually - triangle, hexagon, star, message bubble and more - with a live preview and copy-ready CSS.
Border-Radius Generator
Asymmetric border-radius with all 8 corner values, live preview and shape presets (pill, blob, leaf, ticket).
Cubic-Bezier Generator
Visual cubic-bezier editor with animated preview and 12 industry-standard easing presets.
CSS Filter Generator
Live CSS filter playground with sliders for blur, brightness, contrast, saturate, sepia, grayscale, invert, hue-rotate and opacity.
Glassmorphism Generator
Frosted-glass CSS with live preview - tune background colour, backdrop blur, border and shadow over a busy backdrop.
Image Converter
Convert PNG, JPG, WebP and AVIF in your browser - no upload, no signup.
Image Resizer
Resize images by pixels or percentage in your browser - no upload.
Image Compressor
Shrink JPG and WebP file size with a quality slider and live before/after preview.
Image to Base64
Convert an image to a Data URI (base64) with ready-to-paste CSS and HTML snippets - or paste a Data URI to preview the image.
Image Cropper
Crop images by dragging a selection - free or fixed aspect ratios (1:1, 4:3, 16:9, 9:16).
Image Color Picker
Drop an image, click any pixel, get its hex, RGB and HSL - and build a swatch palette as you go.
Programming16
JSON Formatter & Validator
Format, minify and validate JSON instantly.
Base64 Encoder / Decoder
Encode and decode Base64 strings (text and files).
URL Encoder / Decoder
Percent-encode and decode URLs and query strings.
Hash Generator (SHA-1, SHA-256, SHA-384, SHA-512)
Compute cryptographic hashes of text in your browser.
JWT Decoder
Decode and inspect JSON Web Tokens locally.
Regex Tester
Test and debug regular expressions with live highlights.
Markdown to HTML Converter
Convert Markdown to HTML and back, with a live preview.
YAML to JSON Converter
Convert YAML to JSON and back, in your browser.
CSV to JSON Converter
Convert CSV to JSON and back, with custom delimiter.
SQL Formatter
Pretty-print SQL with consistent keyword casing and line breaks.
HTML Entity Encoder / Decoder
Encode and decode HTML entities, named and numeric.
Cron Expression Reader
Decode a cron expression into plain English plus the next 5 run times.
XML Formatter
Pretty-print or minify XML with proper indentation - in your browser, no upload.
HTML Minifier
Strip whitespace, comments and quotes from HTML - in your browser, with a before/after size report.
Mock Data Generator
Generate fake user records - name, email, phone, address - as JSON or CSV. No signup, no API call.
Markdown Table Generator
Build a Markdown table from rows and columns with column alignment - or paste CSV / TSV and get the table back.
Generators8
Lorem Ipsum Generator
Generate placeholder text by paragraphs, sentences or words.
Password Generator
Generate strong, random passwords right in your browser.
QR Code Generator
Create QR codes for URLs, Wi-Fi, contacts and plain text.
UUID Generator
Generate v4 (random) and v7 (time-sorted) UUIDs in bulk.
Random Number Generator
Cryptographically secure random integers, with range, count and uniqueness.
List Randomizer
Shuffle a list, pick N random items, or draw a single winner - cryptographically fair.
Dice Roller
Roll N dice with M sides (d4 / d6 / d20 / custom) - cryptographically random, in your browser.
Username Generator
Generate random usernames - adjective + noun + number, or pick a theme. All client-side.
Why Arnaud.app?
Private by default
Most tools run entirely in your browser. Your data never leaves your device.
Fast
Static pages, instant results. No spinners, no upsells, no popups.
Free, no signup
No account, no paywall, no watermark. Just tools.
Free online tools, built for speed and privacy
Arnaud.app is a curated collection of 80 free online tools spanning calculators, converters, text utilities, design helpers, developer tools and generators. From everyday tasks - converting kilometres to miles, counting words in an essay, calculating BMI or a mortgage payment - to developer chores like decoding a JWT token or formatting JSON, the right tool is one click away.
Every tool is free, no signup required, no ads injected into the interface, no paywall after a handful of uses. Most run entirely in your browser, so the text, files, passwords or JSON you paste never leave your device. The site is statically generated, weighs less than 200 KB per page, and opens instantly even on a slow connection.
New tools are added regularly. The catalogue grows in response to what people actually search for - quick unit and currency conversions, no-fuss generators, common calculators, and the developer utilities that don't deserve a desktop app.