Harshil Shah
Developer & Founder
Ahmedabad, India
Harshil Shah
Developer & Founder · Stax
Harshil is the developer and founder of stax.tools — a collection of 300+ free, privacy-first tools that run entirely in your browser. No uploads, no accounts, no data leaving your device. Built with Next.js, TypeScript, and Tailwind CSS.
He writes about developer tools, browser APIs, privacy-first architecture, and practical engineering patterns for web applications. Based in Ahmedabad, India.
ARTICLES
Posts by Harshil
Does an Online Tool Upload Your File? A 2-Minute Test
Does an online tool upload your file? Use the browser's Network tab and an offline test to check any video, PDF or image tool in two minutes.
Resistor Color Code Chart: How to Read 4, 5 and 6 Bands
Resistor color code chart with worked examples: read 4, 5 and 6-band resistors, find which end to start from, and decode 8.2k vs 82k correctly.
Regex in 8 Steps: Patterns Every Developer Actually Uses
Learn regex patterns step by step, from literal characters to lookaheads, with 12 real-world patterns to copy into production and the mistakes that break them.
From Login to Dashboard: How JWTs Work, Step by Step
How JWTs work, request by request: how the token is created, what each part holds, how servers validate it without a database call, and the security pitfalls.
Git Rebase vs Merge: 8 Questions That Settle the Debate
Git rebase vs merge: when to merge, when to rebase, when interactive rebase fits, and why 'never rebase public branches' is cited but rarely understood.
Mobile Screen Sizes in Pixels: What Developers Need to Know
Mobile screen sizes in pixels: standard phone dimensions, iPhone and Android widths, device pixel ratio and the CSS breakpoints that matter in 2026.
Compress a Video Without Uploading It (2026 Guide)
Compress video without uploading it: shrink a video by 50–80% for WhatsApp, email or the web, right in your browser. Step-by-step guide with presets.
Diff Checker Guide: How It Works and 6 Use Cases
How diff algorithms work, unified vs split diff formats, why character-level diffs matter and practical diff checker uses beyond version control.
UTF-8, Unicode and Character Encoding: A Developer Guide
Why mojibake happens, how Unicode code points map to UTF-8 bytes, how ASCII, Unicode and UTF-8 differ and why 'just use UTF-8' still needs understanding.
CSS Grid in 2026: How to Actually Use Subgrid
CSS subgrid has had full cross-browser support since 2023. Learn the Grid basics, how subgrid solves alignment problems and when Grid beats Flexbox.
JSON vs XML vs YAML: Choosing the Right Data Format
JSON vs XML vs YAML: a scenario-first comparison of syntax, use cases, performance, readability and schema validation, and where each format wins.
How to Read and Write a Cron Expression: The Complete Guide
Understand cron syntax step by step: the five fields, special characters, common patterns, timezone pitfalls and how to validate expressions before deploying.
URL Encoding Explained: Why Links Break and How to Fix Them
What percent-encoding is, which URL characters must be encoded, encodeURI vs encodeURIComponent in JavaScript and the production bugs it causes.
IP Address, Subnet Mask and CIDR Explained Simply
IP address and subnet mask CIDR notation (/24, /16) explained: what the octets mean, how to find the broadcast address and host range, and when to use a tool.
CORS Errors Explained: Why Browsers Block and How to Fix
CORS errors explained: why the Same-Origin Policy exists, what each error means, how preflight requests work and which server headers fix the problem.
UUID vs ULID vs NanoID: Which ID Format in 2026?
UUID vs ULID vs NanoID compared on format, length, sortability, collision odds and database performance, with a decision guide for your next project.
How to Generate a Strong Password (and Skip Memorizing)
How to create a strong password: how entropy works, why 'P@ssw0rd' loses to 'correct-horse-battery-staple', and using a private in-browser generator.
Create a QR Code for a URL, WiFi, Contact or WhatsApp
Create a QR code for URLs, WiFi, contacts, WhatsApp links or text in your browser. No signup, no upload, no server; everything encodes locally.
Convert Images to WebP Without Uploading: Complete Guide
Convert images to WebP in your browser: files are 25–35% smaller than JPG at the same quality, with no upload or account. Plus when WebP is the wrong choice.
Base64 Encoding Explained: What It Is and When to Use It
Base64 encoding turns binary data into text so it can travel through text-only channels. How it works, where it's used and the mistakes developers make.
What is a JWT? How to decode and verify JSON Web Tokens
JSON web tokens (JWTs) are everywhere in web auth, but what's inside? Learn to decode, read and verify them instantly without installing anything.
How to minify CSS and JavaScript without a build tool
You don't need Webpack or Vite to minify CSS and JavaScript. Shrink assets in the browser, on the command line or inside your editor.
Regex Cheat Sheet: Patterns Every Developer Needs
A practical regex cheat sheet: character classes, quantifiers, groups, lookaheads and the 12 most useful everyday patterns, with live examples.
SHA-256 vs MD5: which hash algorithm should you use?
SHA-256 vs MD5: MD5 is everywhere but broken for security, and SHA-256 is the modern default. What the difference means for your code, files and passwords.
How to Merge PDFs Without Uploading Them Anywhere (2026 Guide)
Merge PDFs without uploading them to any server: combine invoices, contracts, bank statements and scanned IDs into one file, right in your browser.
PNG vs JPG vs WebP vs AVIF: Which Format in 2026?
PNG vs JPG vs WebP vs AVIF: a practical 2026 guide with file-size benchmarks, browser support and when each format wins.
Send a WhatsApp Message Without Saving the Number (2026)
WhatsApp without saving number: three reliable ways to message someone without adding them as a contact, using wa.me links, QR codes and click-to-chat buttons.
How to Compress a PDF Without Uploading It Anywhere
Compress a PDF without uploading it: most online compressors send your file to a server. Reduce PDF size to a limit you choose, free, in your browser.
Developer Tools for Beginners: 12 Browser Utilities
Developer tools for beginners: 12 browser utilities that need no install, handle tasks you'd otherwise Google, and work on any device.
10 Browser-Based Alternatives That Don't Upload Your Data
Privacy-first tools that run entirely in your browser: no uploads, no server processing, no account. Your files and data stay on your device.
Stax vs Smallpdf, JSONLint and TinyPNG: Browser vs Cloud
Browser vs cloud tools: five honest comparisons of Stax with popular SaaS alternatives, where each wins, and how to verify the privacy claims yourself.
Cookie Consent in 2026: What Site Owners Must Do
Consent Mode v2, IAB TCF v2.2 and the EU Digital Markets Act are all live. Here's what site operators must ship to stay compliant and keep AdSense revenue.
Format JSON Without Uploading Data: A 2026 Guide
Format JSON without uploading it: most online formatters send your data to a server, which is risky for production data. Do it in your browser instead.
Why we built Stax Tools
300+ free online tools that all run in your browser. Here's why we built Stax and how it's different from the other tool sites.