Client-side tools
Fast tools that run in your browser.
Mavis Tools is a growing collection of focused utilities for writers, developers, marketers, students, and operators. No account needed. No backend by default.
Tools
120 browser-only utilities, grouped by the jobs people actually repeat.
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Word Counter
Count words, characters, sentences, paragraphs, and reading time instantly.
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Character Counter
Count characters with and without spaces for bios, ads, titles, and posts.
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Case Converter
Convert text to uppercase, lowercase, title case, sentence case, and slug case.
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Reading Time Calculator
Estimate reading time from pasted text using adjustable words per minute.
Security
Password Generator
Generate strong random passwords locally with length and character options.
Developer
JSON Formatter
Format, minify, and validate JSON in the browser without uploading data.
Developer
URL Encoder Decoder
Encode or decode URL components safely in your browser.
Developer
Base64 Encoder Decoder
Encode text to Base64 or decode Base64 back to readable text.
Marketing
CPM Calculator
Calculate CPM, ad spend, or impressions for marketing campaigns.
Finance
Loan Payment Calculator
Estimate monthly loan payments from amount, interest rate, and term.
Health
Percentage Calculator
Calculate percentages, percentage change, and what percent one number is of another.
Finance
Tip Calculator
Calculate tip, total bill, and split amount per person.
Finance
BMI Calculator
Estimate body mass index from US or metric height and weight inputs.
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Age Calculator
Calculate exact age in years, months, and days from a birth date.
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Unit Converter
Convert common length and weight units instantly.
Developer
Color Converter
Convert HEX colors to RGB and HSL values with a live swatch.
Developer
Timestamp Converter
Convert Unix timestamps to local dates and dates back to timestamps.
Developer
Hash Generator
Generate SHA-256, SHA-384, and SHA-512 hashes from text in your browser.
Developer
UUID Generator
Generate random UUID v4 values for development and testing.
Developer
Aspect Ratio Calculator
Calculate missing width or height while preserving aspect ratio.
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Lorem Ipsum Generator
Generate placeholder words, sentences, and paragraphs for mockups and drafts.
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Random Number Generator
Generate random numbers within a custom range using browser crypto.
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List Sorter
Sort lines alphabetically, reverse them, or sort by length.
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Duplicate Line Remover
Remove duplicate lines while preserving or sorting the remaining items.
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Text Diff Checker
Compare two text blocks line by line and see added, removed, and changed lines.
Developer
Markdown Previewer
Preview common Markdown formatting as HTML in your browser.
Developer
Regex Tester
Test JavaScript regular expressions against sample text and view matches.
Developer
Cron Expression Explainer
Explain simple five-field cron expressions in plain English.
Security
JWT Decoder
Decode JWT header and payload locally without verifying signatures.
Developer
CSV JSON Converter
Convert simple CSV data to JSON arrays in your browser.
Developer
JSON CSV Converter
Convert JSON arrays of objects into CSV text locally.
Developer
HTML Entity Encoder Decoder
Encode or decode HTML entities for snippets, docs, and templates.
Developer
CSS Minifier
Minify CSS by removing comments, whitespace, and extra separators.
Developer
JavaScript Minifier
Lightly minify JavaScript snippets by removing comments and whitespace.
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Text Reverser
Reverse characters, words, or lines in pasted text.
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Slug Generator
Generate clean URL slugs from titles, headings, and filenames.
Marketing
UTM Builder
Build campaign URLs with source, medium, campaign, term, and content parameters.
Image
Image Resizer
Resize images in your browser and download the resized file.
Image
Image Format Converter
Convert images to PNG, JPEG, or WebP locally in your browser.
Image
Image Metadata Viewer
View basic image dimensions, type, size, and filename locally.
Finance
Mortgage Calculator
Estimate monthly mortgage payments from price, down payment, rate, and term.
Finance
Savings Calculator
Estimate future savings from starting balance, monthly deposits, rate, and years.
Finance
ROI Calculator
Calculate return on investment from cost and final value.
Finance
Sales Tax Calculator
Calculate tax amount and final price from subtotal and sales tax rate.
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GPA Calculator
Calculate GPA from course grades and credit hours.
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Grade Calculator
Calculate weighted course grade from scores and assignment weights.
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Time Duration Calculator
Calculate the duration between two dates and times.
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Countdown Timer
Run a simple countdown timer in your browser.
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Temperature Converter
Convert Celsius, Fahrenheit, and Kelvin instantly.
Developer
Data Storage Converter
Convert bytes, KB, MB, GB, and TB using decimal units.
Finance
Profit Margin Calculator
Calculate profit, margin, and markup from cost and selling price.
Finance
Markup Calculator
Calculate selling price and profit from cost and markup percentage.
Finance
Break Even Calculator
Calculate break-even units from fixed cost, unit price, and variable cost.
Finance
Unit Price Calculator
Compare price per unit for packages, groceries, and subscriptions.
Finance
Fuel Cost Calculator
Estimate trip fuel cost from distance, mileage, and gas price.
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Date Add Calculator
Add or subtract days, weeks, months, and years from a date.
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Days Between Dates Calculator
Calculate the number of days between two dates.
Health
Pace Calculator
Calculate pace per mile from distance and time.
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Speed Distance Time Calculator
Calculate speed from distance and time.
Finance
Simple Interest Calculator
Calculate simple interest from principal, rate, and time.
Marketing
Meta Length Checker
Check title and meta description length for SEO snippets.
Marketing
Title Preview Tool
Preview a simple search result snippet from title, URL, and description.
Developer
Robots.txt Generator
Generate a simple robots.txt file with sitemap and disallow rules.
Developer
Sitemap URL Generator
Turn a list of paths into absolute sitemap-ready URLs.
Developer
Redirect Generator
Generate simple redirect rules for common static hosting formats.
Developer
Color Contrast Checker
Check contrast ratio between foreground and background HEX colors.
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Character Frequency Counter
Count how often each character appears in text.
Marketing
Keyword Density Checker
Calculate how often a keyword appears in pasted text.
Finance
Invoice Total Calculator
Calculate subtotal, discount, tax, and final invoice total.
Finance
Discount Calculator
Calculate sale price and savings from original price and discount percent.
Finance
Compound Interest Calculator
Estimate compound interest from principal, rate, time, and contribution.
Finance
Paycheck Calculator
Estimate net pay from gross pay, taxes, deductions, and pay frequency.
Finance
Hourly Salary Calculator
Convert hourly wage to weekly, monthly, and annual salary estimates.
Finance
Currency Format Converter
Format numbers as USD, EUR, GBP, INR, or JPY currency strings.
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Roman Numeral Converter
Convert numbers to Roman numerals and Roman numerals back to numbers.
Developer
Binary Decimal Converter
Convert binary numbers to decimal and decimal numbers to binary.
Developer
IP Subnet Calculator
Calculate IPv4 network, broadcast, mask, and usable host range from CIDR.
Developer
DNS Lookup Helper
Generate DNS lookup commands for A, AAAA, CNAME, MX, TXT, and NS records.
Developer
HTTP Status Code Lookup
Look up common HTTP status codes and their meaning.
Developer
HTML Table Generator
Generate simple HTML tables from CSV-style rows.
Developer
CSV Table Generator
Generate a Markdown table from CSV-style rows.
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Whitespace Cleaner
Trim lines, collapse spaces, remove blank lines, and normalize text spacing.
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Line Number Adder
Add line numbers to pasted text with configurable start and separator.
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Text Alphabetizer
Sort words or comma-separated items alphabetically.
Marketing
Open Graph Generator
Generate Open Graph and Twitter card meta tags for a webpage.
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Word Frequency Counter
Count how often each word appears in pasted text.
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Sentence Counter
Count sentences, words, characters, and estimated reading time.
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Paragraph Counter
Count paragraphs, words, sentences, characters, and reading time.
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Letter Counter
Count letter and character frequency in pasted text.
Developer
JSON String Escape
Escape and unescape text for use inside JSON strings.
Developer
URL Parser
Break a URL into protocol, host, path, query, and hash parts.
Marketing
Email Subject Line Tester
Check email subject and preview text length.
Marketing
YouTube Title Length Checker
Check title and description length for YouTube drafts.
Finance
Rent Split Calculator
Split rent, utilities, and shared costs between roommates.
Finance
Credit Card Payoff Calculator
Estimate months and interest to pay off a credit card balance.
Finance
VAT Calculator
Add or remove VAT from a price.
Health
Calorie Deficit Calculator
Estimate daily calorie target from maintenance calories and desired deficit.
Health
Macro Calculator
Split daily calories into protein, carbs, and fat grams.
Health
Body Fat Calculator
Estimate body fat percentage from BMI, age, and sex.
Health
Water Intake Calculator
Estimate daily water intake from body weight and activity.
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Number to Words
Convert numbers into English words.
Developer
ASCII Converter
Convert text to character codes and codes back to text.
Finance
Average Calculator
Calculate the mean average from a list of numbers.
Finance
Median Calculator
Find the median value from a list of numbers.
Finance
Standard Deviation Calculator
Calculate population and sample standard deviation from numbers.
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Recipe Scaler
Scale ingredient amounts from original servings to target servings.
Developer
REM PX Converter
Convert CSS rem values to pixels and pixels back to rem.
Developer
CSS Clamp Calculator
Generate a responsive CSS clamp value from min and max sizes.
Developer
Screen PPI Calculator
Calculate screen pixel density from resolution and diagonal size.
Developer
Color Palette Generator
Generate tints and shades from a base HEX color.
Marketing
Keyword Idea Generator
Generate long-tail keyword ideas from a seed topic.
Marketing
Search Intent Classifier
Classify keywords as informational, commercial, transactional, or navigational.
Marketing
Meta Robots Generator
Generate meta robots tags for index, follow, snippet, and archive controls.
Marketing
Hreflang Generator
Generate hreflang link tags from language and URL pairs.
Marketing
Schema Markup Generator
Generate simple JSON-LD schema for article, product, local business, or FAQ pages.
Marketing
YouTube Tag Generator
Generate video tag ideas from a topic and modifiers.
Marketing
Hashtag Generator
Generate clean social hashtags from keywords or a caption.
Finance
Amortization Calculator
Estimate loan payment, total interest, and first-year principal/interest split.
Finance
Inflation Calculator
Estimate future value after inflation over time.
Finance
Retirement Savings Calculator
Estimate retirement savings growth from starting balance, monthly contribution, and return.