The Developer's
Utility Toolkit
Format JSON, convert string cases, compare code diffs, and process data in milliseconds. Lightning-fast, beautifully designed, and entirely free.
Handcrafted Developer Tools
Every tool is built with an obsession for speed, privacy, and beautiful design.
JSON Formatter & Validator
Format, prettify, and validate massive JSON strings instantly. No server round-trips — entirely client-side.
API Client — Postman Alternative
Test REST APIs directly in your browser. Supports all HTTP methods, headers, auth, collections, history, and environment variables.
JSON ↔ XML Converter
Convert JSON to XML and XML to JSON instantly. Two-way conversion with formatting, validation, and 100% browser-based privacy — no data ever leaves your device.
JSON ↔ YAML Converter
Convert JSON to YAML and YAML to JSON instantly. Perfect for Kubernetes, Docker Compose, CI/CD configs, and API specs. 100% browser-based — private and free.
CSV ↔ JSON Converter
Convert CSV to JSON and JSON to CSV instantly. Handles headers, nested objects, and custom delimiters. Perfect for data migration and API work. 100% browser-based.
Text Case Converter
Instantly convert strings between camelCase, snake_case, PascalCase, UPPER CASE, and more.
Diff Checker
Compare two strings or code blocks to find exact differences line by line with color highlighting.
Regex Tester
Test your regular expressions against sample text in real-time with live match highlighting.
Markdown Preview
Write and preview Markdown in real time. Convert Markdown to HTML with a live editor, toolbar, and instant rendering.
Word & Character Counter
Count words, characters, sentences, and paragraphs. See reading time, speaking time, and keyword density.
URL Parser
Break down complex URLs into individual components — query params, protocol, host, and more.
Base64 Encode / Decode
Securely encode or decode strings to and from Base64 directly in your browser.
Hash Generator
Generate MD5, SHA-1, SHA-256, SHA-384, and SHA-512 hashes for text and files. Verify file integrity instantly.
Password Generator
Generate cryptographically secure passwords, passphrases, and PINs with strength scoring and crack-time estimates.
Amount to Words Converter
Convert amounts to words for cheques, invoices, and legal documents. Supports USD, INR, EUR, GBP with Lakhs and Crores.
Time Format Converter
Convert between 24-hour and 12-hour time formats instantly. Supports bulk conversion and military time.
EMI Calculator with Prepayment
Calculate home loan, car loan, or personal loan EMI with full repayment schedule. Add part payments to see interest saved and tenure reduced. 100% browser-based.
GST Calculator (India)
Calculate GST instantly — add GST or extract GST from inclusive amounts. Supports 5%, 12%, 18%, 28% slabs with CGST/SGST/IGST split. Free and Indian-business friendly.
Income Tax Calculator FY 2025-26
Calculate income tax for FY 2025-26 (AY 2026-27). Compare old vs new tax regime instantly. Includes standard deduction, 80C, HRA, and all major deductions for salaried Indians.
Age Calculator
Calculate exact age in years, months, and days from any date. See total months, weeks, days, hours, and minutes lived. Perfect for documents, birthdays, and milestones.
Date Difference Calculator
Calculate days, weeks, months, and years between two dates. Add or subtract days from a date. Perfect for project planning, deadlines, and event countdowns.
BMI Calculator
Calculate your Body Mass Index instantly. Supports metric (kg/cm) and imperial (lbs/ft) units. See BMI category, healthy weight range, and ideal weight for your height.
Image Compressor
Compress JPG, PNG, and WebP images up to 95% smaller without visible quality loss. Reduce file size for WhatsApp, email, and websites — 100% browser-based, your photos stay private.
PDF Tools — Merge, Split, Compress
Merge multiple PDFs into one, split a PDF into pages, or compress PDF size — all in your browser. No uploads, no signups, completely private and free.
Color Picker & Converter
Pick colors and convert between HEX, RGB, HSL, and CMYK formats. Check contrast ratios for accessibility.
QR Code Generator
Generate QR codes for URLs, text, WiFi, email, and phone numbers. Customize colors and size, then download as PNG.
Embroidery File Viewer
Preview DST embroidery design files online. View stitch patterns, colors, dimensions, and download as PNG or PDF.
Lightning Fast
All processing happens client-side using optimized JavaScript. No server round-trips, no latency — just pure speed.
Private & Secure
Your data never leaves your browser. Zero tracking, zero server storage. What you paste stays on your machine.
Beautiful Design
A meticulously crafted dark & light theme interface with smooth animations. Tools should be a joy to use.
Why Use StringToolsApp?
As software developers, we frequently need to quickly format a JSON payload, convert text cases for a variable, or compare two blocks of code. While there are thousands of online tools available, the vast majority are slow, cluttered with intrusive pop-up ads, or worse — they require you to send your sensitive data to external servers.
StringToolsApp is engineered differently. We leverage modern web technologies to process your data entirely client-side. This means when you paste a JSON file or encode a password to Base64, your data never leaves your browser. It is secure by default.
Beyond privacy, client-side processing makes our tools lightning fast. Paired with a meticulously designed, dark-mode-first user interface, StringToolsApp is built to be the premium utility suite you bookmark and use every single day to supercharge your developer workflow.