Javid
Senior Software Engineer & Founder
Javid is a senior software engineer and founder of SelfDevKit. He builds developer tools with a focus on privacy, offline capability, and native performance.
He also builds products like DroneBundle.com using SelfDevKit. Every tool in SelfDevKit started as something he needed himself.
Articles by Javid
Date to Timestamp Unix: Convert Any Date to Epoch Time Correctly
Date to timestamp unix conversion is not symmetric. Learn the timezone each language assumes, the DST traps, and code for 8 platforms.
Crontab: The Command, Its Flags, and How to Edit Schedules Safely
Crontab explained: what every flag does, how crontab -e really works, which flags change meaning between systems, and how to avoid wiping your jobs.
x-api-key: The API Key Header Explained, With Code and Gotchas
x-api-key is the de facto header for API key auth. How to send it, validate it, fix CORS and AWS 403 errors, and why header casing bites you.
Cron and Crontab: How the Daemon, the File, and the Command Fit Together
Cron and crontab explained: what the daemon does, where crontab files live on disk, the sixth field, and the gotchas that make jobs fail silently.
JSON to CSV: Flatten Nested Data Without Corrupting It
Convert JSON to CSV without corrupting your data: flattening strategies, RFC 4180 escaping, code in Python, Node and jq, plus CSV injection risks.
SQL Query Formatter: How to Read Logged and ORM-Generated SQL
A SQL query formatter turns logged, ORM-generated, one-line SQL into readable queries. Here is the full cleanup workflow, from log line to EXPLAIN.
Formatter SQL: How SQL Formatters Work and Where They Break
Formatter SQL explained: how SQL formatters parse queries, why dialect matters, and where they break on templates, placeholders, and embedded SQL.
Diff Checker: The Complete Guide to Comparing Text, Code, and Data
Learn what a diff checker is, the different types, how they work, and how to compare text and code privately offline.
How to Generate an SSH Key: The Complete Developer Guide
Learn how to generate an SSH key with ssh-keygen, choose ed25519 vs RSA, add a passphrase, and keep your private key off untrusted servers.
What Is an API Key? How They Work, Look, and Stay Secure
What is an API key? A plain-English guide to how API keys work, what they look like, how to send them, and how to generate and store them securely.
Crontab Guru: How to Read and Build Cron Expressions
What crontab guru is, how its cron editor works, and how to read any cron expression yourself, plus a private offline alternative.
How to Test Regex: A Practical Guide to Testing Patterns That Work
Learn how to test regex the right way: write test cases, handle engine flavor differences, catch catastrophic backtracking, and debug patterns offline.
RSA Key Generator: How to Create RSA Key Pairs Safely
Use an RSA key generator to create public and private key pairs in PEM format. Learn key sizes, formats, and why generating keys offline matters.
Markdown Editor Online: Write, Format, and Export Markdown Safely
A markdown editor online lets you write and preview markdown in real time. Compare the best editors, learn the syntax, and keep drafts private.
Markdown Viewer Online: Preview, Render, and Debug Markdown Safely
Learn how a markdown viewer online renders your text, why GFM previews differ, and how to preview markdown privately without a browser tab.
Lorem Ipsum Paragraph: Copy Blocks, Word Counts, and Layout Testing
Copy ready-made lorem ipsum paragraphs, learn how long each one is, and test multi-paragraph typography. Offline generator for developers.
GUID Generator Online: Formats, Code, and a Private Alternative
Generate GUIDs online, learn the .NET format specifiers, and see why an offline GUID generator keeps your identifiers off unknown servers.
HTML Encode: How Entity Encoding Works and When to Use It
Learn how to HTML encode special characters, why entity encoding stops XSS, and how it differs from URL encoding. With code examples and an offline tool.
Word Counter Online: How They Work and When to Go Offline
A word counter online tallies words and characters instantly. Compare the top online tools and learn when an offline counter keeps your text private.
Image Resizer: How to Resize Images Without Losing Quality
Learn how an image resizer works, which resampling algorithm to pick, and how to resize images offline without uploading private files to a server.
Image to Base64: Encode, Embed, and Automate the Right Way
Convert image to base64 with data URIs, code examples in JS, Python, and Node, plus build-tool automation for CSS and HTML embedding.
SHA256 Generator: How to Generate and Verify SHA-256 Hashes
Learn how a SHA256 generator works, generate hashes in JS, Python, Go, and the CLI, and fix the reasons two SHA-256 hashes never match.
Word Counter: The Developer Guide to Counting Words, Characters, and More
A word counter for developers. Count words, characters, and bytes in your text. Learn counting techniques and why offline tools keep content private.
JSON Formatter Online: Format, Validate, and Debug JSON the Right Way
Use a JSON formatter online to beautify and validate JSON data. Learn the best tools, privacy risks, and code examples.
Lorem Ipsum Text: What It Means, Where It Comes From, and How to Use It
Lorem ipsum text explained: its origin from Cicero, what the Latin actually means, ready-to-copy blocks, and developer use cases.
Text Compare: How to Find Differences Between Two Texts Fast
Learn how to text compare two documents using diff tools, CLI commands, and code examples across languages.
JSON Validator: How to Find and Fix JSON Errors Fast
Use a JSON validator to find syntax errors fast. Fix common mistakes and validate programmatically in JS and Python.
JSON Compare: How to Diff Two JSON Objects and Find Every Difference
Learn how to JSON compare with code examples, CLI tools, and visual diff viewers to find every difference fast.
JSON Viewer: How to Explore, Navigate, and Debug JSON Data
Learn how to use a JSON viewer to explore nested data, debug API responses, and navigate large JSON files with tree view.
Base64 Encoder: How to Encode Data in Every Language and the CLI
Learn how to use a base64 encoder in JavaScript, Python, Go, Rust, and the command line. Covers UTF-8 pitfalls, URL-safe encoding, and output size.
Lorem Ipsum Generator: The Developer Guide to Placeholder Text
Use a lorem ipsum generator to create placeholder text for layouts, testing, and prototyping. Code examples, use cases, and offline tools.
Base64 Decode: How to Decode Base64 Strings, Files, and Data
Learn how to base64 decode strings in every major language, the CLI, and desktop tools. Covers troubleshooting, URL-safe variants, and privacy.
Crontab Generator: How to Build and Debug Cron Expressions
Learn cron syntax, build expressions with a crontab generator, and debug cron jobs that fail silently.
Unix Timestamp Converter: How Epoch Time Works and How to Convert It
Use this unix timestamp converter guide with code examples in 6 languages, seconds vs milliseconds reference, and Y2038 explained.
SQL Formatter Online: Best Tools and Why Offline Might Be Better
Compare the best SQL formatter online tools and learn when offline formatting is the safer, faster choice for developers.
Code Diff Checker: How to Compare Code and Read Diff Output
Learn how to use a code diff checker to compare files, read unified diff output, and spot changes fast.
JSON to TypeScript: How to Generate Type-Safe Interfaces from JSON
Convert JSON to TypeScript interfaces automatically. Learn manual and automated approaches with real code examples.
RGB Color Picker: How RGB Works, CSS Syntax, and Developer Workflows
Use an RGB color picker to find exact color values, convert formats, and write modern CSS with confidence.
Image Converter: The Developer Guide to PNG, JPG, WebP, and More
An image converter transforms files between PNG, JPG, WebP, GIF, and TIFF. Learn each format and why offline conversion matters.
SQL Formatter: How to Beautify and Format SQL Queries
Learn how to format SQL queries for readability. Covers style conventions, code examples, and offline formatting tools.
URL Parser: How to Break Down and Debug URLs Like a Pro
Learn how a URL parser breaks URLs into components like protocol, host, path, and query strings for faster debugging.
HTML Formatter: Beautify, Minify, and Validate HTML the Right Way
Learn how to use an HTML formatter to beautify messy markup, minify for production, and validate your code offline.
UUID Generator: How to Create Unique IDs (v4, v7, ULID, and More)
Generate UUIDs and unique IDs for your projects. Learn which version to use, how they work, and why UUID v7 is replacing v4.
Hex Color Picker: The Developer Guide to Color Formats, Contrast, and Workflows
Use a hex color picker to find exact color codes, convert between formats, and check WCAG contrast.
How to Decode JWT Tokens: GUI, CLI, and Code Methods
Learn how to decode JWT tokens using desktop tools, command-line one-liners, and code in JavaScript, Python, and Go.
Base64 to Image: Decode, Convert, and Troubleshoot
Learn how to convert base64 to image and back with code examples in JavaScript, Python, and Node.js, plus fixes for the most common decoding errors.
JWT Secret Key Generator: How to Create Secure Signing Keys
Learn how to generate a JWT secret key that actually meets RFC 7518 requirements, plus the format decisions developers always get wrong.
JSON to Dart: The Complete Guide for Flutter Developers
Learn every approach to JSON to Dart conversion: manual fromJson, json_serializable, and freezed, with real-world nested object examples.
JSON Minify: How to Compress JSON and Where It Actually Helps
Learn how to JSON minify for production, cut file sizes by up to 40%, and avoid the privacy risks of pasting sensitive data into online tools.
How to Unescape JSON: A Practical Guide for Developers
Learn how to unescape JSON strings in Python, JavaScript, and Go with code examples and debugging tips.
From Web to Native: Building iOS Apps with SelfDevKit Developer Tools
Learn how I use SelfDevKit to build native iOS applications like FeelClose, a long-distance couples app. From debugging Supabase APIs to decoding JWTs, see the developer tools that power mobile development.
Building Real-World Services with SelfDevKit: A Developer Case Study
Learn how I use SelfDevKit to build production services like Is It Visible, a mountain visibility forecasting platform. From JSON debugging to URL encoding, see the developer tools that power real projects.
Regex Tester Guide: Learn Regular Expressions with Practical Examples
Master regex with this comprehensive regex tester guide. Learn regex syntax, common patterns for validation, capture groups, and how to test expressions effectively with real-world examples.
Hash Generator Guide: MD5, SHA256, and Cryptographic Hashing Explained
Learn how hash generators work and when to use MD5, SHA256, SHA512, or BLAKE. Understand hashing for file integrity, password security, and API authentication with practical examples.
Base64 Encode and Decode: Complete Guide for Developers
Learn how to base64 encode and decode text and images. Understand data URIs, when to use Base64, and how to convert images to Base64 strings for HTML, CSS, and APIs.
Secure Password Generator: The Complete Guide to Creating Unbreakable Passwords
Learn how to generate truly secure passwords in 2025. Understand password entropy, strength analysis, and why offline generators are the only safe choice for your credentials.
JWT Decoder & Validator: The Complete Guide to JSON Web Tokens
Learn how to decode, validate, and debug JWT tokens securely. Understand JWT structure, algorithms, claims, and why offline decoders protect your authentication secrets.
JSON Formatter, Viewer & Validator: The Complete Guide for Developers
Learn how to format, view, validate, and debug JSON data efficiently. Discover the best JSON tools for developers and why offline formatters protect your sensitive API data.
Why Offline-First Developer Tools Matter More Than Ever
Discover why privacy-focused, offline developer tools are essential in 2025. Learn how local processing protects your API keys, JWT tokens, and sensitive data while delivering instant performance.
Getting Started with SelfDevKit: The Complete Guide to 50+ Offline Developer Tools
Master SelfDevKit from installation to advanced workflows. Learn how to use JSON tools, JWT decoder, ID generators, and 50+ developer utilities to boost your productivity while keeping your data completely private.