Technical articles
Technical articles on JavaScript, cybersecurity and web tools. No fluff.
60fps CSS animations: transform, opacity and the performance rules
Why animating width or top wrecks performance while transform/opacity don't: the rendering pipeline, will-change, GPU compositing and prefers-reduced-motion.
HTTP caching explained: Cache-Control, ETag and stale-while-revalidate
How HTTP caching really works: max-age, s-maxage, ETag vs Last-Modified, 304 validation, stale-while-revalidate and the headers you must master.
How a QR code works inside: modules, masks and error correction
QR code engineering: module structure, finder patterns, versions, Reed-Solomon correction that lets broken codes scan, and why there are 8 masks.
What a CDN is and how it speeds up your web even from another continent
How a CDN works: edge locations, cache at the edge, TLS terminated near the user, DDoS protection and when your site truly needs one.
Dark mode with CSS variables: full theming without duplicating styles
How to build professional dark mode: custom properties as tokens, prefers-color-scheme, manual toggle with data-attribute and transition without flash.
Deploy strategies: rolling, blue-green and canary without surprises
How to deploy with zero downtime: rolling updates, blue-green, canary releases, feature flags and the rollback you never rehearsed.
Secrets management: how not to leak API keys, .env files or tokens
Where project secrets should live and how to protect them: environment variables, .env in gitignore, rotation after leaks and secrets managers.
Git rebase vs merge: which to use and the branching flows that work
When to merge and when to rebase, resolving conflicts without panic, interactive rebase for history cleanup and which branch flows fit your team.
PostgreSQL indexes explained: EXPLAIN, B-tree and the N+1 hell
Why your query takes 3 seconds: how B-tree indexes work, reading EXPLAIN ANALYZE, the ORM N+1 problem and when an index won't help.
SQL JOINs explained: INNER, LEFT, RIGHT and FULL with clear examples
The four fundamental joins with real example tables: what each returns, combining with WHERE, self-joins and the classic mistakes.
Passkeys and WebAuthn explained: the end of passwords
How passkeys work: FIDO2 public-key cryptography, why they can't be phished, cross-device sync and how to implement them in your app.
Advanced Linux permissions: setuid, sticky bit and umask explained
Beyond rwx octal: special bits setuid/setgid/sticky, how umask works, default permissions and the real-world cases where each one matters.
Docker networking explained: bridge, host, ports and container communication
How containers communicate: default bridge, custom networks with internal DNS, host networking, publishing ports right and debugging connectivity.
Schema.org and JSON-LD explained: the structured data Google rewards
What structured data is: schema types, JSON-LD step by step, real rich results, validation and the mistakes that waste your SEO.
Monitor your website free: uptime, certificates, domains and alerts before disaster
Know your site is down before your users do: uptime monitors, healthchecks, certificate and domain alerts, and status pages.
Essential web accessibility: WCAG in practice without dying trying
The highest-impact accessibility fundamentals: semantic HTML, keyboard, contrast, ARIA when needed and how to audit your site for free.
Video codecs explained: H.264, H.265, VP9 and AV1 without unnecessary jargon
How video compression works: keyframes, inter/intra prediction, why AV1 weighs half of H.264 and which codec to choose for web in 2026.
REST API design: the conventions separating a good API from a mess
Resources, verbs, status codes, versioning, pagination and idempotency: practical guide to designing coherent REST APIs others enjoy consuming.
OAuth 2.0 and OpenID Connect explained: the flows you actually use
How Google or GitHub login works: OAuth2 vs OIDC difference, authorization code flow with PKCE, tokens, scopes and implementation mistakes.
What happens when you type a URL and hit Enter: the complete journey
The full journey of a web request: DNS, TCP, TLS, HTTP, browser rendering. Every layer explained in order, no gaps.
XSS explained: how the attack works and how to block it with CSP
Cross-Site Scripting from scratch: XSS types, real injection examples, sanitization, HttpOnly cookies and a properly configured Content Security Policy.
End-to-end encryption: what E2EE is and what it actually protects
How end-to-end encryption works: HTTPS difference, Diffie-Hellman key exchange, Signal's double ratchet and what E2EE does NOT protect.
How image compression works: DCT, quantization and DEFLATE
Inside JPEG, PNG and WebP: DCT transform, quantization, prediction and entropy coding. Understand why some losses are visible and others aren't.
How a PDF works inside: objects, xref and why it weighs what it weighs
A PDF's internal structure: header, body, xref table, compressed streams and embedded fonts. Understand why some PDFs weigh 100 KB and others 50 MB.
How passwords are stored on a server: salt, bcrypt and Argon2
What should happen to your password inside the server: why it's never stored as-is, how salt, pepper, bcrypt and Argon2id work, and classic mistakes.
Color spaces explained: sRGB, P3, gamma and why your colors shift
Why a color looks different on every screen: gamuts, sRGB and Display P3 spaces, gamma and transfer functions, and how to define colors correctly in CSS.
3-2-1 backups: the verified copy strategy with SHA-256
How to design a backup system that actually works: 3-2-1 rule, automation, integrity verification with hashes and restore testing.
Gzip and Brotli: how HTTP compression works and how to enable it
HTTP compression explained: LZ77, Huffman, Brotli windows, compression levels, what to compress and what not, plus Nginx and CDN configuration.
JSON vs YAML vs TOML: which configuration format to choose
Technical comparison of the three dominant formats: syntax, each one's traps, tooling support and when to use JSON, YAML or TOML.
Advanced regex: lookarounds, groups and catastrophic backtracking
Beyond regex basics: lookahead and lookbehind, backreferences, named groups and how to avoid catastrophic backtracking that hangs servers.
SSH tunnels: local, remote and dynamic port forwarding explained
How SSH tunnels work: local and remote forwarding, dynamic SOCKS proxy, real use cases and the options that avoid common mistakes.
Digital audio explained: sample rate, bit depth and codecs without the hype
What 44.1 kHz and 16 bits really mean, why aliasing exists, how to choose between MP3, AAC, FLAC and Opus, and how it all affects your audio.
How DNS works: resolution, records and why it's sometimes slow
The complete journey of a DNS query: cascading caches, root servers, A/AAAA/MX/CNAME/TXT record types, TTL and how to debug issues with dig.
CORS explained: why your request fails and how to actually fix it
Understand CORS once and for all: Same-Origin Policy, Access-Control headers, OPTIONS preflight requests, credentials and the most common errors with fixes.
Responsive images: srcset and sizes explained with real examples
How to serve the right image to every device with srcset, sizes and picture: pixel density, art direction breakpoints and real bandwidth savings.
JWT vs server sessions: which one for your app (and why)
Technical comparison of stateless JWT auth versus cookie sessions: security, logout, scaling, CSRF and when each model actually fits.
UUID v7 and ULID: unique identifiers that also sort by date
Why random UUID v4 punishes your database indexes and how UUIDv7 and ULID solve it with sortable-yet-unique IDs. Full comparison and code.
Time zones in software: why your app stores dates wrong
UTC, offsets, DST and the golden rule of dates: how to store, calculate and display times correctly plus the classic time zone bugs.
Encryption, hashing and encoding: the three operations everyone confuses
Real differences between encrypting, hashing and encoding: what each guarantees, when to use AES, SHA-256 or Base64 and the most common security mistakes.
SSH keys explained: Ed25519 vs RSA and the OpenSSH format under the hood
How SSH keys work: why Ed25519 is the recommended choice, how to generate pairs in the browser with WebCrypto and what the openssh-key-v1 format contains.
clip-path in CSS: custom responsive shapes without images
Master clip-path in CSS: polygon with percentage coordinates, circle, ellipse, shape animation and why the result is responsive by design.
How HTTPS works: the TLS handshake explained step by step
What really happens when your browser connects over HTTPS: ECDHE key exchange, X.509 certificates, AES symmetric encryption and forward secrecy.
docker-compose.yml explained: services, volumes and networks for your local stack
How to build a complete stack with Docker Compose: Node app + PostgreSQL connected via internal DNS, named volumes vs bind mounts and restart policies.
How to write a modern Dockerfile: layers, multistage and non-root user
Anatomy of a well-built Dockerfile for Node, Next.js, Python, Go and Rust: layer caching, multistage builds, Alpine vs Slim images and non-root users.
Browser fingerprinting: the 11 signals that identify you without cookies
How browser fingerprinting works: canvas, WebGL, audio, fonts and more. How much entropy each signal adds and what actually defends you.
GitHub Actions explained: CI, Vercel deploys and Docker images to GHCR
How GitHub Actions workflows work: triggers, Node version matrix, secrets, least-privilege permissions and three production-ready templates.
Glassmorphism in CSS: how backdrop-filter works and when to use it
Technical guide to glassmorphism in CSS: backdrop-filter blur, translucent borders, performance and accessibility. Generate your glass card ready to copy.
Self-hosting from scratch: your first server with SSH, Docker and Nginx
Complete guide to running your own server: securing SSH with Ed25519 keys, deploying with Docker Compose and publishing with Nginx and HTTPS.
Neumorphism in CSS: dual shadows, pressed states and its limits
How neumorphic design works in CSS: two opposing shadows, colors derived from the background, inset pressed state and why accessibility suffers.
Nginx configuration explained: static sites, SPAs and reverse proxy
The three server blocks you need: try_files for SPAs, reverse proxy with X-Forwarded headers, HTTPS with Let's Encrypt and the add_header inheritance trap.
Pure CSS loading spinners: the border technique and its variants
How to create CSS loaders without JavaScript: the rotating border trick, keyframes, staggered nth-child delays, negative delay and performance notes.
Tuning a Guitar With Your Phone or Browser, No Tuner Required
How a microphone-based guitar tuner works: pitch detection, cents precision and standard EADGBE tuning. Free, nothing to install.
How to Add a Watermark to a PDF for Free
Guide to adding text as a watermark on every page of a PDF, with configurable position, opacity and color. Free and in your browser.
How to Add Page Numbers to a PDF for Free
Guide to numbering PDF pages, choosing position and starting number, free and in your browser. Useful for reports, theses and long documents.
How to Analyze Any Website's Security HTTP Headers (HSTS, CSP, X-Frame-Options)
Guide to reviewing a website's security HTTP headers: HSTS, CSP, X-Frame-Options and more. What they mean and why their absence is a risk.
How to Run a Free On-Page SEO Audit in Under a Minute
Guide to auditing any page's on-page SEO: title, meta description, H1, Open Graph and schema. 19 checks, 0-100 score and actionable quick wins.
How to Run a Complete Technical Audit of Any Website in One Report
Guide to the web analyzer: DNS, WHOIS, SSL, SEO, email security, redirects and tech stack, all in a single report with a 0-100 score.
Base64, Base32, Base58, Base85: When to Use Each Encoding
Guide to the differences between Base64, Base32, Base58, Base85, Hex and URL encoding, and when to use each depending on the context: email, URLs, blockchain.
A Scientific, Programmer and Financial Calculator in One Tool
Guide to the complete calculator: scientific operations, binary/hex/octal and bitwise for development, and mortgages and compound interest for personal finance.
How to Calculate the Right Width or Height Keeping the Aspect Ratio
Guide to calculating proportional width and height (16:9, 4:3, 21:9) from a single dimension, and understanding what a simplified aspect ratio is.
Changing Audio Speed and Pitch Without Sounding Like a Chipmunk
The difference between changing speed with pitch preserved, changing pitch with speed preserved, and the classic sped-up record effect. Great for learning songs by ear.
Censoring a Word in Audio With a Beep, With Exact Precision
How to censor specific sections of an audio file with a beep (bleep), controlling the exact start and end. Mute the original under the beep or leave it audible in the background.
How chmod Works on Linux: From Octal to Symbolic Notation
Guide to understanding Linux permissions (rwx), converting between octal notation (755, 644) and symbolic, and choosing the right permission for each case.
How to Compress a PDF Without Losing Quality
Guide to reducing a PDF's size by removing metadata and optimizing its internal structure, without visible quality loss. Free and in your browser.
How to Look Up a Domain's DNS Records (A, MX, TXT, NS...)
Guide to looking up any domain's DNS records in real time: A, AAAA, MX, TXT, NS, CNAME and SOA. What each type means and when to check it.
How to Count Words, Characters and Reading Time of a Text
Guide to counting words, characters, sentences and paragraphs in real time, calculating reading time and analyzing a text's keyword density.
How to Convert Between 80+ Units: Length, Weight, Temperature and More
Guide to the unit converter: length, weight, temperature, area, volume, speed, digital storage, time and pressure, all in one tool.
Converting Audio Between MP3, WAV, FLAC and Opus: Which Format to Pick
A practical guide to converting audio between MP3, WAV, OGG, FLAC, M4A and Opus in your browser. Lossy vs lossless codecs explained, and which bitrate to use.
How to Convert Photos and Images to PDF for Free
Guide to converting JPG, PNG or WebP to PDF, reordering with drag & drop and adjusting page size and margins. Free, no sign-up and in your browser.
How to Convert Between PNG, JPG, WebP, AVIF, BMP and ICO (and Which to Choose)
Guide to converting images between formats and understanding when to use each: PNG for transparency, WebP and AVIF for modern web, ICO for icons.
How to Convert a PDF to JPG or PNG, Page by Page
Guide to converting each page of a PDF to a JPG or PNG image, with 1x, 2x or 3x resolution. Free, no sign-up and 100% in your browser.
How to Convert Your Code's Indentation Between Tabs and Spaces
Guide to converting any code's indentation between tabs and spaces, with configurable width, and why mixing both breaks readability.
How to Convert Between px, rem, em, vw and vh in CSS (and When to Use Each)
Guide to converting CSS units in real time with configurable base font-size and viewport, and understanding when to use px, rem, em, vw, vh or pt.
How to Create a Complete Favicon From an Image, Text or Emoji
Guide to creating favicons in 8 sizes, Apple Touch Icon and PWA from an image or directly from text/emoji, with the ready-to-use HTML snippet.
How to Create a robots.txt (and Block AI Crawlers Like GPTBot)
Guide to generating a robots.txt with per-bot rules, a sitemap link, and specific blocking of AI training crawlers like GPTBot and ClaudeBot.
How to Create a Markdown Table Without Counting Bars and Dashes by Hand
Guide to creating Markdown tables visually and copying the correct code, ready for GitHub, Notion or Obsidian, with no manual column alignment.
Turning a Song Into a Ringtone: How to Pick the Right Section
How to create a short ringtone from any song, with a smooth fade included. Why the section you pick matters more than the length.
How to Create Clickable Zones on an Image Without Writing Coordinates by Hand
Guide to creating rectangle, circle and polygon clickable zones on an image, with snap to grid and export to HTML or JSON.
What Is My IP and What It Really Reveals
Guide to looking up your public IP or any other address, and understanding what geolocation, ISP and timezone data an IP exposes in real time.
How to Decode an x.509 SSL/TLS Certificate and Understand Its Fields
Guide to decoding an x.509 certificate in PEM format: issuer, validity, SAN, SHA-256 fingerprint and what each field means. Free and 100% in your browser.
How to Discover a Domain's Subdomains (Without Active Scanning)
Guide to finding any domain's subdomains using Certificate Transparency (crt.sh), a passive technique that sends no traffic to the target server.
How to Find Out What Technologies a Website Uses (Framework, CMS, CDN)
Guide to detecting what framework, CMS, server, CDN and analytics any website uses. How technology fingerprinting works and what it's good for.
How to Split a PDF: By Range, Every N Pages, or Page by Page
Practical guide to splitting a PDF: extracting a page range, splitting every N pages, or separating each page into its own file. Free and in your browser.
Why Your MP3s Say "Unknown Artist" and How to Fix It
What ID3 tags on an MP3 actually are, why they're not the same as the filename, and how to edit them (title, artist, album, cover art) without re-encoding the audio.
How to Edit a Photo With Filters, Cropping and Adjustments Without Installing Photoshop
Guide to applying filters (B&W, Sepia, Vintage), cropping, rotating and adjusting brightness and contrast on a photo directly in the browser, no sign-up.
Editing a PDF for Free With No Installs: The 6 Most Common Tasks
Convert images to PDF, merge, split, turn into images, compress and watermark, all free and in your browser. A quick guide to which tool to use for what you need.
How to Trim, Compress and Convert a Video Without Installing Editing Software
Guide to the browser video editor: trim, compress, convert format, rotate, generate a GIF, add a watermark and subtitles, no sign-up.
How to Delete Pages From a PDF Without Rebuilding the Document
Guide to visually selecting and deleting the pages you don't need from a PDF, free and with no sign-up. Download the result without the blank, duplicate or extra page.
Automatically Removing Silence From Audio Without Cutting Natural Pauses
How to remove silence from a long recording (interview, podcast, dictation) without trimming the normal pauses of speech. Threshold in dB and minimum duration explained.
What Is Steganography and How to Hide a Message Inside an Image
Practical guide to LSB steganography: how to hide and reveal text inside a PNG image without it showing at a glance. Free and 100% in your browser.
How to Extract Text From a PDF Without Copying Page by Page
Guide to extracting all the text from a PDF and downloading it as .txt, free and in your browser. No page limit, no uploading the file to any server.
How to Format an Unreadable SQL Query in Seconds
Guide to formatting and beautifying SQL for MySQL, PostgreSQL, SQLite, SQL Server and BigQuery, and why a well-indented query is easier to debug.
Audio Fade In and Fade Out: Why an Abrupt Cut Sounds Bad
How to add a fade in and fade out to an audio clip to avoid the click of an abrupt cut. Recommended duration depending on the type of content.
How to Create CSS Shadows With Multiple Layers (and Why One Is Never Enough)
Visual guide to creating CSS box-shadow with multiple layers: offset, blur, spread, color, opacity and inset, and why real shadows use several layers.
Pure Tone Generator: What an Exact-Frequency Beep Is Actually For
Generate pure tones (sine, square, sawtooth, triangle) at any frequency between 20 Hz and 20 kHz. Real uses: testing speakers, calibrating gear and understanding the human hearing range.
Retro 8-Bit Sound Effects Without Hunting for Licensed Audio Packs
How to generate 8-bit style sound effects (coin, jump, laser, explosion) procedurally, with no samples or pre-recorded audio files. Great for game jams and indie devs.
How to Generate a Correct .gitignore for Your Project
Guide to creating a .gitignore by combining languages, frameworks and editors, and avoiding the most common mistake: committing node_modules, .env or build files.
How to Generate a Harmonic Color Palette From a Single Color
Guide to applied color theory: complementary, analogous and triadic palettes, and how to generate harmonic combinations from a single HEX color.
Why Placeholder Text Is Still Lorem Ipsum (and How to Generate It)
Guide to generating placeholder text in paragraphs, sentences or words, in classic Latin, Spanish or English, and why Lorem Ipsum beats real text.
Recording Audio From the Browser Without Installing Any App
How to record with your microphone directly from the browser, pause and resume, and download the result. Nothing to install, no account, and the recording never leaves your device.
How to Free Up Space on Windows by Cleaning Temp Files, Cache and Prefetch
Guide to what temporary files, browser cache and the Prefetch folder are on Windows, and how to clean them safely and offline.
Online Metronome: Practicing at Reduced Tempo Without Buying Anything
A free metronome from 1 to 1000 BPM with tap tempo and adjustable time signatures. Why a software metronome needs a special technique to avoid drifting out of sync.
How to Minify HTML, CSS and JavaScript So Your Site Loads Faster
Guide to minifying code by removing unnecessary comments and whitespace, and understanding how much real weight is saved in HTML, CSS and JavaScript.
Normalizing Audio Volume with LUFS (Not What You Think)
Why turning up the volume isn't the same as normalizing. What LUFS is, the EBU R128 standard, and the loudness targets for podcast, music and broadcast.
How to Sort Lines and Remove Duplicates From Any List Instantly
Guide to sorting, deduplicating, reversing or shuffling any list of text lines, useful for email lists, tasks or exported data.
What a Diceware Passphrase Is and Why It's More Secure Than a Random Password
Guide to the Diceware method for generating memorable, high-entropy passphrases, combining random words with crypto.getRandomValues.
What Password Entropy Is and How to Measure It in Bits
Guide to understanding a password's entropy in bits, how it's calculated, which common patterns reduce it, and how long it would take to crack by brute force.
What Is WHOIS and How to Find Out Who Registered a Domain
Guide to looking up a domain's WHOIS/RDAP record: registrar, registration and expiry dates, nameservers, and what information is actually public.
Which Software License to Choose for Your Project (MIT, Apache, GPL...)
Guide to understanding the differences between MIT, Apache 2.0, GPL 3.0, BSD and ISC, and generating the correct LICENSE file based on what you want to allow.
How to Remove Accents From Text (While Keeping the Ñ if You Want)
Guide to removing accents from any text instantly, and why the Ñ deserves different treatment from the rest of Spanish diacritics.
How to Trace a URL's Redirect Chain (301, 302...)
Guide to tracing every redirect hop of a URL, with HTTP code and time per hop. Detect long chains that slow down your site.
Trim Audio Online Without Losing Quality: Fast vs Precise Mode
How to trim MP3, WAV, OGG, FLAC or M4A to exact seconds in your browser. The difference between fast (copy) and precise (re-encode) cutting, and when to use each.
How to Resize Several Images at Once and Download Them as a ZIP
Guide to resizing images in batch by percentage or maximum dimension, and downloading the whole result as a single ZIP. Free and in your browser.
Reducing Background Noise From a Recording Without Sounding Robotic
How spectral noise reduction works and why it isn't the same as a simple gate. When a high reduction value starts sounding metallic.
How to Reorder PDF Pages Without Rescanning
Guide to changing the order of PDF pages by dragging and dropping, free and in your browser. Useful for documents scanned out of order.
How to Rotate PDF Pages for Free (Fixing Sideways Scanned Documents)
Guide to rotating PDF pages 90, 180 or 270 degrees, free and without uploading the file to any server. Ideal for documents scanned sideways or upside down.
Isolating a Song's Vocals to Make Karaoke or Sample the Drums
How to split any song into vocals, drums, bass and other instruments with AI (HTDemucs) directly in the browser. For making karaoke tracks, extracting acapellas or studying drum patterns.
How to Run a Fair Random Drawing (and Why Math.random() Isn't Enough)
Guide to picking a random winner from a list with real cryptographic randomness, and why that matters for a drawing to be genuinely fair.
What SPF, DKIM and DMARC Are and How to Check If Your Domain Is Protected
Guide to understanding SPF, DKIM and DMARC, checking whether a domain is protected against email spoofing, and what each verdict means.
How to Use the Pomodoro Technique to Actually Focus
Guide to the Pomodoro technique: why it works, how to structure work and break cycles, and how to use a timer with session statistics.
Text to Speech Online: System Voices vs Local AI, Which to Use
Convert text to speech for free in your browser. The difference between instant system voices and the downloadable neural AI engine, and when to use each.
Transcribing Audio to Text with AI in the Browser (Whisper)
How to transcribe any audio to text with Whisper running locally in the browser. The three available models, voice activity detection (VAD), and why picking the language manually matters.
Merging Several Audio Files Into One, Even With Mixed Formats
How to combine multiple audio files into one, in whatever order you choose, even if they're MP3, WAV and M4A mixed together. Why merging audio isn't as simple as pasting bytes.
How to Check a Website's SSL Certificate and Its Expiry
Guide to checking any site's SSL/TLS certificate: issuer, expiry, SANs, protocol and A+ to F security grade. Free and in real time.
How to Verify a Downloaded File's Integrity With Its SHA Hash
Guide to computing a file's SHA hash and comparing it against the one published by its source, to detect if a downloaded file is corrupted or tampered with.
Seeing Sound: How to Use an Audio Spectrum Visualizer
Visualize the frequencies or waveform of an audio file or your microphone in real time. How to spot clipping at a glance and what the frequency bars actually mean.
HTTP Status Codes Explained: From 200 to 500 (Guide)
What HTTP codes mean: 2xx success, 3xx redirects, 4xx client errors, 5xx server errors. The most important ones (404, 301, 500, 403) explained.
How AI Runs Inside Your Browser (No Servers, No Cloud)
A deep explanation of how artificial intelligence runs 100% in your browser: WebGPU, WebAssembly, ONNX, segmentation models and why this changes the rules.
Core Web Vitals: How to Make Your Website Fast (2026 Guide)
What Core Web Vitals are (LCP, INP, CLS), how to measure them and the real optimizations that improve your site's speed and SEO. A practical guide for developers.
Git Cheatsheet: The Essential Commands (With Examples)
Git cheatsheet with the most-used commands: clone, branches, commits, merge, undo changes, stash and resolving conflicts. A quick reference for developers.
Why Processing Your Data in the Browser Protects Your Privacy
What 'client-side' means, why uploading files to a website is a risk and how local processing gives you back control of your data. Privacy explained.
Regular Expressions: Complete Cheatsheet With Examples
Regex cheatsheet: metacharacters, classes, quantifiers, anchors, groups and lookarounds, plus ready-made patterns (email, phone, URL). Quick reference with examples.
Binary, Decimal and Hexadecimal: Converting Number Bases
Understand number bases: what binary, hexadecimal and octal are, how they convert between each other and why computing uses them. Free converter online.
camelCase, snake_case and More: Converting Text Case
Guide to naming conventions: camelCase, snake_case, PascalCase, kebab-case and when to use each in programming. Convert uppercase and lowercase online.
HEX, RGB and HSL: Understanding and Converting CSS Colors
Guide to CSS color formats: what HEX, RGB and HSL are and when to use each, alpha/transparency and how to convert colors free in the browser.
How to Create a QR Code for Free (URLs, WiFi, vCard and More)
Guide to creating QR codes for free: QR types, error correction levels, design best practices and how to generate them in the browser with no watermark.
How to Compare Two Texts and See the Differences (diff)
What a diff is, how to compare two texts or file versions to see what changed, and what it's used for in programming and document review. Free diff online.
Compress Images Without Losing Quality: Complete 2026 Guide
How to compress JPG, PNG and WebP images, cutting file size without visible quality loss. Format differences, the optimal level and free batch compression.
Convert CSV to JSON (and JSON to CSV): A Complete Developer Guide
How to correctly convert CSV to JSON and JSON to CSV: structure, quotes, commas inside fields, data types and free in-browser conversion.
How to Create a Strong Password (and Why Yours Aren't)
Guide to creating strong passwords: length, entropy, managers, passphrases and common mistakes. Generate strong passwords free and 100% in your browser.
How to Scan Documents to PDF with Your Phone for Free (No Apps)
Learn to scan documents with your phone camera and turn them into PDF for free, with perspective correction, filters and OCR, all in the browser and uploading nothing.
CSS Gradients: Linear, Radial and Conic (Guide With Examples)
Learn to create CSS gradients: linear-gradient, radial-gradient and conic-gradient, color stops, angles and transparency. Generate gradients free online.
Your Photos' EXIF Metadata: What It Reveals and How to Remove It
Photos store EXIF metadata: GPS location, date, camera model and more. Learn what it reveals about you and how to view and remove it to protect your privacy.
How to Optimize SVG and Reduce the Size of Your Icons
Why exported SVGs are too heavy and how to optimize them: metadata, decimals, junk code from editors. Reduce your SVG size for free online.
What Is Base64 and When to Use It (With Examples)
A clear guide to Base64: what it is, how it works, what it's for in images and data URIs, why it isn't encryption and how to encode and decode free in the browser.
What Is a Hash: MD5, SHA-256 and What It's Really For
A clear explanation of hash functions (MD5, SHA-1, SHA-256): what they are, what they're for, why they aren't encryption and how to generate hashes free in the browser.
What Is JSON and How to Format and Validate It Correctly
JSON guide for developers: syntax, types, common errors, how to format (pretty print) and validate JSON, and how to do it free in the browser.
What Is a JWT and How to Decode It (Developer Guide)
Understand JSON Web Tokens: header.payload.signature structure, claims, how to decode a JWT and why they should never store sensitive data.
What Is Markdown: Complete Syntax Guide With Examples
Learn Markdown from scratch: headings, lists, links, images, tables, code and more. The full syntax with examples and how to convert Markdown to HTML.
What Is a Slug and How to Create SEO-Friendly URLs
Learn what a slug is, why it matters for SEO and how to create friendly URLs: lowercase, hyphens, no accents or stop words. Generate slugs free online.
URL Encoding: What It Is, When to Encode a URL and How
Guide to URL encoding (percent-encoding): which characters to escape, the difference between encodeURI and encodeURIComponent and how to encode free online.
How to Remove an Image Background for Free Without Uploading Anything
Complete guide to removing a photo background for free, with AI and 100% in your browser. No watermark, no sign-up and your image never leaves your device.
Cron Syntax Explained: How to Schedule Tasks Step by Step
Learn cron syntax: the 5 fields, asterisks, ranges, lists and steps, with real examples. Build cron expressions free and understand them instantly.
How to Merge and Split PDFs for Free Without Uploading Anything
Guide to merging several PDFs into one or splitting a PDF into parts, free and in the browser. No watermark, no limits and your documents never leave your device.
AES-256-GCM Encryption in the Browser with Web Crypto
Learn to encrypt and decrypt text directly in the browser with AES-256-GCM and PBKDF2 using the native Web Crypto API. No external libraries, 100% private.
Regular Expressions in JavaScript: Complete Guide
Learn regex from scratch with JavaScript. Full syntax, capture groups, flags, lookaheads and the 10 most useful patterns with real-world examples.
What is a Unix Timestamp and the Year 2038 Problem
Understand what Unix time (epoch time) is, how to convert it in JavaScript, and why 32-bit systems will have a problem on January 19, 2038.
Generate UUID in JavaScript: crypto.randomUUID() Guide
Learn to generate v4 UUIDs in JavaScript using the native crypto.randomUUID() API. UUID vs GUID differences, when to use them, and how to generate in bulk.
JavaScript
Native browser functions, Web APIs, cryptography with Web Crypto, UUID generation, regular expressions and modern JavaScript patterns without external dependencies.
Cybersecurity
AES-256-GCM encryption, key derivation with PBKDF2, best practices for safe handling of sensitive data on the frontend and how to protect user privacy in web applications.
Web tools
How to build tools that run 100% in the browser without servers, without sign-ups and without compromising user data. Performance, privacy and user experience as core principles.