All 373 Free Online Developer Tools
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11 categoriesAll Tools
AlphabeticalChess Move Validator - Free Legal Move Checker Online
Free chess move validator. Play chess on an interactive board with real-time legal move validation. No signup. Perfect for learning chess rules.
Click Speed Test - CPS & Reaction Time
Free click speed test (CPS) and reaction tester. Measure clicks per second over 1-100 seconds, right-click, spacebar or touch. No signup, 100% private.
Code Minifier & Beautifier - JS, CSS, HTML
Free online code minifier and beautifier. Minify JS, CSS, HTML for production or beautify for debugging. Size stats, copy, all in browser. No signup.
PopularCode to Image Converter - Create Beautiful Code Screenshots
Convert your source code into stunning syntax-highlighted PNG images. Choose from 7 themes, customize padding & fonts, and share beautiful code.
Color Blindness Simulator - CVD Test
Free color blindness simulator. Test how images and colors appear with 8 types of color vision deficiency (protanopia, deuteranopia, tritanopia). WCAG.
Color Contrast Checker - WCAG AA AAA
Free WCAG color contrast checker. Check if text and background colors meet AA and AAA accessibility standards. Real-time contrast ratio, pass/fail.
Color Palette Generator - Create Harmonious Color Schemes
Free color palette generator. Create harmonious schemes with 7 harmony rules. Export as CSS, Tailwind, SCSS, JSON. Lock colors, WCAG checker. No signup.
Color Picker - HEX RGB HSL Converter
Pick colors and convert between HEX, RGB, and HSL formats with live preview and copy buttons. Free, browser-based, 100% private.
Compound Interest Calculator - Free Investment Growth Tool
Free compound interest calculator. Calculate investment growth with monthly contributions, compounding frequency, and year-by-year breakdown. No signup.
Concrete Calculator - Free Slab, Footing & Bag Estimator
Free concrete calculator for slabs, footings, columns, and stairs. Get cubic yards, cubic meters, bag counts (40/60/80 lb), mix ratio breakdown, and waste.
Condom Size Calculator - Find Your Exact Fit
Free condom size calculator. Enter girth and length in mm, cm or inches to get your nominal width range and a fit verdict for any condom. 100% private.
PopularConnections Game - Free Word Puzzle Online
Play Connections word puzzle free. Group 16 words into 4 hidden categories. Unlimited puzzles, 4 difficulty levels, hints and a timer. No signup.
PopularCORS Header Generator - Allow-Origin Tool
Free CORS header generator. Configure Allow-Origin, methods, headers, credentials. Generate Nginx, Apache, Express, Flask, Workers snippets.
Cover Letter Generator - Free AI Builder
Free AI cover letter generator. Create professional, ATS-friendly cover letters in seconds. 4 tones, multiple templates, download as TXT. No signup, 100%.
Cron Expression Evaluator & Explainer
Paste a cron expression and get its plain-English meaning, the next 10 run times in your timezone, and the traps that break it silently.
NewCron Generator - Build Cron Expressions & Preview Runs
Generate cron expressions interactively. Pick minute, hour, day, month and weekday, then preview the next 5 runs your schedule will produce.
Cross Stitch Pattern Maker - Photo to DMC Chart
Free cross stitch pattern maker. Convert any photo to a printable DMC cross-stitch chart with thread color matching, symbols, Aida count, and PDF export.
Crossword Puzzle Maker - Free Printable Crossword
Free crossword maker. Turn answers and clues into a real interlocking crossword with answer key. Print or save PDF, export PNG, solve online. 100% private.
NewCrypto Price Tracker - Live Prices and Charts
Free crypto price tracker. Live prices for 17,000+ coins via CoinGecko, market cap, 24h volume, and trending list. AI cannot show real-time crypto prices.
CSS Animation Generator - Live Preview
Free CSS animation generator with live preview. Build custom @keyframes animations, 15 ready-made presets, fine-tune timing and easing, and copy CSS.
CSS Box Shadow Generator - Live Preview
Free CSS box shadow generator. Multi-layer shadows, depth presets, inset toggle, live preview. Copy production-ready CSS. No signup, 100% browser-based.
CSS Filter Generator - Visual CSS Filter Builder
Free CSS filter generator. Visually create CSS filter effects for images and elements. Blur, brightness, contrast, grayscale, sepia, hue-rotate and more.
CSS Flexbox Generator - Visual Flex Layout Builder
Free CSS flexbox generator with interactive visual builder. Create responsive flex layouts with direction, wrap, justify, align, gap. Copy CSS code.
CSS Formatter and Validator - Beautify or Minify CSS
Free online CSS formatter and validator. Beautify messy CSS, minify for production, fix syntax errors. Instant results, no signup required.
CSS Gradient Generator - Linear, Radial, Conic
Free CSS gradient generator. Linear, radial and conic gradients with live preview, an angle dial and multiple color stops. Copy CSS or export SVG.
PopularCSS Grid Generator - Visual Layout Builder
Free CSS grid generator with drag-and-drop builder. Create responsive grid layouts, columns, rows, gaps. Copy production CSS.
CSS Specificity Calculator - Compute Selector Weight
Free CSS specificity calculator. Compute a,b,c values for any selector instantly. Understand selector weight and cascade priority. No signup.
NewCSS to Tailwind Converter - Free Online Tool
Free CSS to Tailwind converter. Convert CSS properties to Tailwind utility classes instantly. 100+ properties supported.
CSV to SQL INSERT Generator - DDL, Batches, Upserts
CSV, Excel or JSON to CREATE TABLE plus batched INSERT statements for PostgreSQL, MySQL, SQLite, SQL Server and Oracle, with a data quality report first.
cURL to Code Converter - Python, Node, Go, PHP, C#
Convert curl commands to Python, Node, Go, PHP, or C# code. Deterministic parser, 100% in-browser, no upload, no signup, and free to use forever.
Daily Horoscope - Personalized Astrology and Charts
Free personalized daily horoscope. Sun sign, moon sign and 2026 forecasts computed from real planetary positions with astronomy-engine. 6 languages.
PopularDate Calculator - Days Between Dates & Date Arithmetic
Free online date calculator. Calculate days between dates, add or subtract days/weeks/months/years from any date, and compute business days. 100% private.
Days Until Calculator - Countdown to Any Date
Free days until calculator. Countdown to any date: Christmas, birthday, holiday, or event. See how many days, hours, minutes left. No signup required.
Debt Payoff Calculator - Snowball & Avalanche Free
Free debt payoff calculator. Compare avalanche vs snowball, see your debt-free date, total interest, and month-by-month payoff plan. No signup.
DNS & WHOIS Lookup - Check Domain Records
Free DNS lookup and WHOIS checker. Query DNS records (A, AAAA, MX, NS, SOA, TXT) and domain registration info instantly. No signup required.
Dog Age Calculator - Dog Years to Human Years
Free dog age calculator. Convert dog years to human years with AVMA + UCSD formulas. Breed presets, life stages, chart. No signup, private.
Domain Age Checker - Free WHOIS Domain Age Lookup
Free domain age checker. Check how old any domain is, creation date, expiry date, registrar, and nameservers. Instant WHOIS lookup, no signup required. AI.
Drawing Board - Free Online Whiteboard & Sketch Pad
Free online drawing board and whiteboard. Sketch, draw shapes, add text, and save as PNG. No signup, no upload, 100% private browser-based canvas tool. AI.
Due Date Calculator - Ovulation, LMP & IVF
Free due date calculator. Work out your due date from LMP, conception date or IVF transfer, with ovulation and fertile-window dates.
Electricity Cost Calculator - kWh Rate, Bill, Appliances
Price every appliance on your electric bill from your own kWh rate. Daily, monthly and yearly cost per device, in your browser, free.
NewEmail Authentication Checker - SPF DKIM DMARC Check Online
Free email authentication checker. Check SPF, DKIM, and DMARC DNS records for any domain. Fix email deliverability. We check real DNS records.
Email Header Analyzer - SPF, DKIM & DMARC Verdict
Read raw email headers: SPF, DKIM, DMARC and ARC verdicts, alignment against the From domain, delivery delay attributed to one hop, and spoofing signals.
NewEmail Spam Checker - Spam Score & Deliverability Test
Free email spam checker. Score subject, preheader and body against 552 weighted spam triggers, then get a fixed rewrite. 100% private.
NewEmail Verifier - Verify Email Addresses Instantly
Free email verifier. Check if email addresses are valid and can receive messages. Detect disposable emails and SMTP issues. No signup required.
Engagement Rate Calculator - Multi-Platform Social Media
Free engagement rate calculator. 6 platforms (IG/TikTok/YT/X/FB/LI), 3 formulas, 5 tier benchmarks, weighted engagement. No signup.
PopularEnglish Dictionary - Definition, Pronunciation, Synonyms
Free English dictionary with real-time definitions, US and UK audio pronunciation, phonetic transcription, synonyms, antonyms and examples. 100% private.
EPUB to PDF Converter - Free Online
Free EPUB to PDF converter in your browser. Real selectable text, cover page, table of contents with page numbers, page size and font controls. No upload.
Excel Formula Translator - #NAME? Fixer & Function Names
Translate an Excel formula between 17 spreadsheet languages and find the #NAME? cause. Function names, argument separators and a 490-function reference.
NewExcel to PDF Converter - Free Online XLSX to PDF
Free online Excel to PDF converter. Convert XLSX and XLS files to PDF directly in your browser. Preserves tables, multiple sheets, and formatting.
Excel Viewer - Free Online XLSX Viewer & Converter
Free online Excel viewer and converter. View XLSX, XLS, CSV files without Excel. Convert to JSON, CSV format. 100% private browser processing, no upload.