The Kordu Blog

iyda15 Apr 202611 min read

How to Split a Restaurant Bill Fairly (Every Method)

Even split, itemized, one person pays — all 3 bill-splitting methods explained with real math. Includes tip, tax, shared items, and awkward situations.

iyda15 Apr 202612 min read

PDF vs Word: When to Use Each Format

PDF locks layout for sharing; DOCX stays editable for collaboration. Learn which format to use, when to convert, and the most common mistakes.

iyda15 Apr 202613 min read

Social Media Image Sizes 2026: The Complete Guide

Every social media image size for 2026 in one place. Covers Instagram, Facebook, X, LinkedIn, TikTok, YouTube, Pinterest, and Threads with pixel dimensions.

Security

EXIF Data: What Your Photos Reveal and How to Remove It

Photos embed GPS coordinates, device model, and timestamps in EXIF data. 87% of smartphone photos contain location metadata. Learn how to strip it.

iyda14 Apr 202612 min read

iyda14 Apr 202614 min read

Image Compression Explained: Lossy vs Lossless

Learn how lossy and lossless image compression work. JPEG quality 80 cuts file size 75% with no visible loss. Real size comparisons and format guide.

iyda14 Apr 202613 min read

Markdown Cheat Sheet: The Complete Syntax Reference

Every Markdown syntax element in one reference. Tables, code blocks, task lists, footnotes, and platform differences. Used by 14M+ GitHub repos.

CalculatorsFeatured

BMI Calculator: How to Calculate and Understand Your Body Mass Index

Calculate your BMI instantly with our free online calculator. Learn what BMI means, its categories, limitations, and when to consult a doctor.

iyda13 Apr 20264 min read

iyda13 Apr 202612 min read

Cron Expression Cheat Sheet: Every Schedule You'll Ever Need

Copy-paste cron expressions for every schedule from every-minute to yearly. 20+ ready-to-use examples with plain-English translations and field reference.

iyda13 Apr 202614 min read

The Fibonacci Sequence in Nature, Art, and Code

Explore the Fibonacci sequence from sunflower spirals to algorithm design. 92% of sunflower heads follow Fibonacci spiral patterns (Royal Society, 2016).

iyda13 Apr 202612 min read

What Your IP Address Reveals About You (It's More Than You Think)

Your IP address exposes your city, ISP, and browsing habits to every site you visit. 76% of websites log IPs. Here's exactly what they see.

iyda12 Apr 202611 min read

How to Compare Text and Code Files Online

Learn how diff works, how the Myers algorithm finds minimal edits, and how to compare text, code, configs, and JSON files in seconds online.

iyda12 Apr 202614 min read

CSS Flexbox & Grid Cheat Sheet: Every Property Explained

Complete CSS Flexbox and Grid reference with every property, values, and visual examples. 92% of sites now use Flexbox or Grid for layout.

iyda12 Apr 202613 min read

How to Improve Your Aim in FPS Games

Improve your FPS aim with proven techniques. Covers crosshair placement, eDPI, arm vs wrist aiming, aim trainer routines, and common mistakes to fix first.

Fun

Random Picker: Spinning Wheel for Decisions, Teams, Classrooms

Use a spinning wheel picker for fair random selection. Covers classrooms, team meetings, personal choices, and how uniform randomization actually works.

iyda12 Apr 202610 min read

iyda11 Apr 202615 min read

Mouse Polling Rate Explained: 125Hz vs 500Hz vs 1000Hz+

See real mouse polling rate input lag from 125Hz to 8000Hz, what 1000Hz changes, and whether higher rates are worth the CPU cost.

iyda11 Apr 202613 min read

Mouse Sensitivity Explained: DPI, eDPI, and cm/360

Learn how DPI, eDPI, and cm/360 work together. Pro players average 40-54 cm/360 in tactical shooters. Find your ideal gaming sensitivity with real data.

Data

QR Code Guide: Types, Sizes, Error Correction, Best Practices

Complete QR code guide covering error correction levels, minimum print sizes, static vs dynamic codes, and security risks. 2.2B+ QR scans globally in 2025.

iyda11 Apr 202617 min read

SecurityFeatured

Strong Password Generator: How to Create Uncrackable Passwords in 2026

Generate secure passwords and passphrases with our free tool. Learn what makes a password strong, how crack time estimates work, and best practices for password security.

iyda11 Apr 20264 min read

iyda11 Apr 202611 min read

What Is a UUID? v1 vs v4 vs v7 Explained

UUID v4 is the most widely used identifier format, but RFC 9562 (2024) introduced v7. Learn when to use v1, v4, and v7 for databases and distributed systems.

iyda10 Apr 202611 min read

Base64 Encoding Explained: How It Works and Why

Visual step-by-step guide to Base64 encoding. See how text becomes a 6-bit alphabet used in data URIs, JWTs, and email. Adds ~33% size overhead.

iyda10 Apr 202612 min read

Character Encoding Explained: UTF-8, ASCII, Unicode

UTF-8, ASCII, and Unicode explained with byte-level examples. Learn why mojibake happens, how to fix encoding issues, and why UTF-8 powers 98.2% of the web.

iyda10 Apr 202616 min read

Color Spaces Explained: sRGB, Adobe RGB, P3, and CMYK

Learn when sRGB, Adobe RGB, Display P3, and CMYK matter. Display P3 covers 25% more colors than sRGB. Includes CSS examples and conversion tips.

iyda10 Apr 202610 min read

How to Remove Image Backgrounds for Free

Remove image backgrounds free in seconds using AI. No signup, no upload. Works for product shots, headshots, logos. Save as transparent PNG or WebP.

iyda10 Apr 202613 min read

Unit Conversion Reference: Every Common Conversion Table

Complete unit conversion chart for metric to imperial, temperature, weight, volume, speed, and more. Covers 95% of real-world conversions with exact multipliers.

iyda9 Apr 202615 min read

Best Free WinRAR Alternatives in 2026: 7-Zip, PeaZip, More

Need a free WinRAR alternative? Compare 7-Zip, PeaZip, NanaZip, and built-in Windows extraction, plus when WinRAR is still worth paying for.

How to Compress Images Without Losing Quality

Reduce image file sizes by up to 80% without visible quality loss. Compare JPEG, PNG, and WebP formats. Step-by-step guide with a free online compression tool.

iyda9 Apr 20264 min read

iyda9 Apr 202617 min read

HTTP Status Codes: The Complete Reference Guide

Every HTTP status code from 1xx to 5xx explained with real-world examples. A developer reference covering all 63 standard codes used by 97% of the web.

iyda9 Apr 202613 min read

Image Formats Explained: PNG vs JPG vs WebP vs AVIF vs SVG

Compare PNG, JPG, WebP, AVIF, SVG, and GIF with real file sizes. WebP cuts photo size 25-35% vs JPEG. Find the right format for every use case.

Time Date

Time Zones Explained: UTC, GMT, Offsets, and DST

How the world's 24+ time zones work, why UTC and GMT differ, and how DST shifts scheduling. Covers offsets, IANA database, and conversion tips.

iyda9 Apr 202615 min read

iyda8 Apr 202614 min read

Best Crosshair Settings for Competitive FPS Games

Best crosshair settings for CS2, Valorant, and Apex Legends. Covers style, size, color, and pro settings. 73% of top CS2 pros use a static small cross or dot.

iyda8 Apr 202617 min read

Linux Commands Cheat Sheet: 100 Essential Terminal Commands

The 100 most-used Linux terminal commands with real examples, grouped by task. 97% of servers run Linux (W3Techs, 2025). Bookmark this reference.

FinanceFeatured

Mortgage Calculator: How to Calculate Your Monthly Repayments

Calculate your mortgage monthly payments, total interest, and see a full amortisation schedule. Compare 15, 20, 25, and 30-year mortgage terms.

iyda8 Apr 20265 min read

iyda8 Apr 202614 min read

SSL/TLS Explained: How HTTPS Actually Works

How TLS handshakes, certificate chains, and HTTPS encryption work step by step. TLS 1.3 cuts handshakes to 1 round trip, down from 2 in TLS 1.2.

iyda8 Apr 202612 min read

Statistics Cheat Sheet: Mean, Median, Mode, Std Dev

Statistics cheat sheet with formulas, worked examples, and when to use mean vs median. 90% of data analysis uses these core measures (ASA, 2024).

iyda7 Apr 202610 min read

How to Merge PDF Files for Free (No Watermark)

Combine PDFs free without watermarks. Gmail caps attachments at 25 MB - large merges routinely hit that. Step-by-step for browser, Mac, Windows, mobile.

iyda7 Apr 202614 min read

Number Systems Explained: Binary, Octal, Decimal, Hex

Learn binary, octal, decimal, and hex with step-by-step conversions. Over 60% of developer tools rely on hex notation daily. Practical examples included.

iyda7 Apr 202610 min read

Regex Patterns You'll Actually Use: Copy-Paste Ready

20+ battle-tested regex patterns for emails, URLs, phone numbers, IPs, dates, and more. Copy-paste ready with examples for developers.

Productivity

Typing Speed Benchmarks: Average WPM by Profession

Real typing speed data by profession and age. The average adult types 40 WPM, but transcriptionists hit 75-100. Full WPM tables and improvement tips.

iyda7 Apr 202613 min read

iyda7 Apr 202612 min read

WHOIS Lookup: How to Find Out Who Owns a Domain

Find out who owns any domain with WHOIS lookup. Learn what WHOIS data shows, why it's often hidden, how GDPR changed everything, and how to use it for security research.

Calculators

BMI Chart and Alternatives: Health Metrics That Matter

BMI misclassifies roughly 54 million Americans. Compare BMI to waist-to-hip ratio, body fat percentage, and four other metrics doctors actually use today.

iyda6 Apr 202614 min read

Compound Interest Explained: The Math That Makes You Rich

Learn the compound interest formula with real scenarios. $100/month grows to $227,000+ over 30 years. Includes tables, Rule of 72, and calculator.

iyda6 Apr 20269 min read

iyda6 Apr 202610 min read

Free Alternatives to remove.bg for Background Removal

remove.bg limits free users to low-res previews. These 5 alternatives remove backgrounds for free, including one that runs entirely in your browser.

iyda6 Apr 202611 min read

Best Free Alternatives to Smallpdf and iLovePDF in 2026

The best no-watermark Smallpdf and iLovePDF alternatives for compressing, merging, splitting, and converting PDFs without free-tier caps.

iyda6 Apr 202615 min read

SQL Cheat Sheet: Queries, Joins, Functions

SQL cheat sheet with JOIN diagrams, window functions, and query patterns. 70% of developer queries use the same 20 SQL commands (Stack Overflow, 2025).

Security

WebRTC Leaks Explained: Why Your VPN Might Not Protect You

WebRTC leaks expose your real IP even with a VPN active. 23% of VPN users are vulnerable. Learn how to test and disable WebRTC in every browser.

iyda6 Apr 202613 min read

iyda5 Apr 202614 min read

Color Theory for Web Designers: A Practical Guide

Learn color harmony rules with real hex values. 90% of snap judgments about products are based on color alone. Build better palettes today.

iyda5 Apr 202616 min read

File Size Reference: How Big Is a Megabyte, Really?

Visual file size guide: 1 MB holds 500 text pages or 1 compressed photo. Byte to petabyte explained with real-world comparisons and storage planning tips.

iyda5 Apr 202610 min read

Free Alternatives to Adobe Photoshop for Quick Image Edits

Photoshop costs ~$22/month. Most people use 10% of it. Here are the best free alternatives for quick edits, browser tools, and desktop apps.

iyda5 Apr 202611 min read

How Mortgage Payments Are Calculated: The Full Formula

Learn the mortgage payment formula step by step. See how a $300K loan at 6.5% becomes $1,896/month with real amortization schedules and breakdowns.

iyda5 Apr 202611 min read

SHA-256 vs MD5 vs SHA-1: Which Hash Algorithm Should You Use?

MD5 collisions were cracked in 2004. SHA-1 fell in 2017. Here's which hash algorithm is safe today and when to use SHA-256, SHA-512, or BLAKE3.

NetworkFeatured

What Is My IP Address? Public vs Private IP Explained

Find your public IP address instantly. Learn the difference between public and private IPs, how geolocation works, and how to protect your privacy online.

iyda5 Apr 20264 min read

iyda4 Apr 202613 min read

Free Alternatives to Adobe Acrobat in 2026

Adobe Acrobat Pro costs $239.88/year. Here are the best free alternatives for merging, compressing, converting, and signing PDFs in 2026.

iyda4 Apr 202615 min read

Free Alternatives to Adobe Express in 2026

Adobe Express locks its best features behind a $9.99/month subscription. Here are the best free alternatives for background removal, image resizing, social media graphics, and quick edits in 2026.

iyda4 Apr 202616 min read

Free Alternatives to Adobe Lightroom in 2026

Adobe Lightroom costs $9.99/month for 1TB or $19.99/month for Creative Cloud. Here are the best free alternatives for photo editing, RAW processing, and photo management in 2026.

iyda4 Apr 202611 min read

JSON Formatter: How to Beautify, Validate, and Minify JSON

Format, beautify, and minify JSON instantly with our free online tool. Learn about common JSON errors, when to minify vs beautify, and best practices for working with JSON.

iyda4 Apr 20264 min read

SecurityFeatured

How Long Does It Take to Crack a Password in 2026?

See real password crack times by length and character set, from 4 to 20 characters, plus the defenses that actually matter.

iyda4 Apr 202613 min read

Stretched Resolution in Competitive FPS: Does It Help?

Stretched resolution makes models look wider but doesn't change hitboxes. 57% of CS2 pros use 4:3 stretched. Here's what actually changes and whether it helps.

DeveloperFeatured

Best Free Online Developer Tools in 2026

A curated list of the best free browser-based developer tools for 2026. JSON formatters, regex testers, hash generators, UUID tools, and more — all running in your browser.

iyda3 Apr 20264 min read

iyda3 Apr 202613 min read

CIDR Notation and Subnetting Made Simple

Learn CIDR notation and subnetting with visual binary breakdowns. Includes a full /8 to /32 cheat sheet covering all 25 prefix lengths and real examples.

iyda3 Apr 202611 min read

How to Compress a PDF Without Losing Quality

Reduce PDF file size by 40-70% without visible quality loss. Learn what makes PDFs large, how compression works, and when not to compress.

iyda3 Apr 202612 min read

CPS Test: What Is Clicks Per Second and How to Improve It

Average users click 6-8 CPS. Learn what CPS is, how techniques like butterfly and jitter clicking work, and where click speed actually matters.

Calculators

How to Scale a Recipe Up or Down (Without Ruining It)

Scale recipes for any serving count using the right math. Covers leavening, eggs, spices, cooking time, pan size, and baker's percentages. With a free tool.

iyda3 Apr 202611 min read

DataFeatured

QR Code Generator: How to Create Custom QR Codes for Free

Create custom QR codes instantly with our free online generator. Choose colors, sizes, and error correction levels. Perfect for business cards, menus, and marketing.

iyda3 Apr 20264 min read

Regex Cheat Sheet: A Complete Guide to Regular Expressions

Master regular expressions with our comprehensive cheat sheet. Test patterns live, learn character classes, quantifiers, lookaheads, and see 10 practical examples.

iyda3 Apr 20265 min read

iyda2 Apr 202614 min read

Average Reaction Time by Age: Chart, Ranges, and Peak Age

See average human reaction time by age, when reflexes peak, normal ms ranges, and what actually improves reaction speed.

Convert Images to WebP Format (And Why You Should)

Learn why WebP is the best image format for the web. Convert PNG and JPG to WebP instantly. Compare file sizes, quality, and browser support across all major formats.

iyda2 Apr 20264 min read

iyda2 Apr 202616 min read

D&D 5e Ability Scores: What Every Stat Does and How to Build

Master D&D 5e ability scores with point buy analysis, class stat priorities, and modifier math. 74% of optimized builds start with a 16 in their primary stat.

iyda2 Apr 202614 min read

DPI vs PPI: Image Resolution Explained for Print and Screen

DPI vs PPI explained with real pixel math. Learn why 300 DPI matters for print, what PPI means for screens, and how to export images correctly.

iyda2 Apr 202615 min read

Git Commands Cheat Sheet: From Basics to Advanced

Complete git cheat sheet with 50+ commands, real examples, and ASCII branch diagrams. Used by 100M+ developers worldwide. Bookmark this reference.

iyda2 Apr 202610 min read

HEIC Explained: What It Is and How to Convert to JPG/PNG

HEIC files are Apple's photo format since iOS 11 (2017), storing images at half the size of JPEG. Learn why they break on Windows and how to convert them.

iyda2 Apr 202614 min read

How Much to Tip: A Complete Guide by Country and Situation

Tipping norms by country: US 18-20%, UK 10-15%, Japan no tipping, Australia optional. Covers restaurants, hotels, taxis, and the pre-tax vs post-tax debate.

Productivity

Keyboard Shortcuts Every Professional Should Know (2026)

Master 100+ keyboard shortcuts for Windows, Mac, VS Code, browsers, and Google Docs. Shortcut users save 8 days/year per Brainscape. Full reference.

iyda2 Apr 202616 min read

iyda1 Apr 202613 min read

How to Create Animated GIFs from Images

Learn how to create animated GIFs from a series of images. Covers frame rate, file size, the 256-color limit, and when to use WebP or MP4 instead.

iyda1 Apr 202613 min read

FOV in FPS Games: How It Affects Your Aim and Performance

Learn how FOV affects aim, FPS, and motion sickness in shooters. Per-game FOV defaults for CS2, Valorant, Apex. 68% of pros use 100-110 HFOV.

Text

Free Alternatives to Grammarly in 2026

Grammarly Premium costs $12/month. Here are the best free alternatives for grammar checking, spell checking, and writing assistance in 2026 — including tools built into apps you already use.

iyda1 Apr 202616 min read

iyda1 Apr 202614 min read

Lorem Ipsum Alternatives: 30+ Placeholder Text Generators

30+ lorem ipsum alternatives from bacon to baseball. 73% of designers use placeholder text (Adobe, 2024). Find the right generator for your project.

iyda1 Apr 202614 min read

Monitor Refresh Rates Explained: 60Hz vs 144Hz vs 240Hz vs 360Hz

Frame time math for 60Hz to 360Hz monitors with real diminishing returns data. 144Hz cuts frame time by 10ms over 60Hz, and here's what matters for gaming.

iyda1 Apr 202616 min read

SPF, DKIM, and DMARC Explained: Stop Emails Going to Spam

How SPF, DKIM, and DMARC work together to stop email spoofing and spam folders. Google now rejects 75% of unauthenticated email from bulk senders.

iyda1 Apr 202614 min read

WCAG Contrast Ratios Explained: AA vs AAA Compliance

Learn WCAG contrast ratios with real examples. AA needs 4.5:1 for text, AAA needs 7:1. Fix failing color combos with practical tools and techniques.

iyda31 Mar 202614 min read

API Authentication Methods Compared: OAuth, JWT, API Keys

Compare API authentication methods with real HTTP examples. OAuth 2.0, JWT, API keys, and session tokens explained. 78% of breaches involve weak auth.

iyda31 Mar 202616 min read

DNS Record Types Explained: A, AAAA, CNAME, MX, TXT

Every DNS record type explained with real dig examples. Covers A, AAAA, CNAME, MX, TXT, NS, SOA, PTR, SRV, and CAA records used across 350M+ domains.

iyda31 Mar 202615 min read

Free Alternatives to Canva in 2026

Canva Pro costs $15/month and locks its best templates and AI tools behind the paywall. Here are the best free alternatives for graphic design, image editing, and social media graphics in 2026.

iyda31 Mar 202611 min read

JSON vs XML vs YAML vs TOML: When to Use Each Format

Compare JSON, XML, YAML, and TOML with real config examples. 70% of APIs use JSON (Postman, 2025) - learn which format fits your use case.

iyda31 Mar 202618 min read

Mechanical Keyboard Switch Comparison Chart for 2026

Compare mechanical keyboard switches by type, force, travel, and sound. See the chart for Cherry MX, Gateron, Kailh, and the best picks for gaming vs typing.

Productivity

Pomodoro Technique: The Science Behind Timed Work Sessions

Brief breaks during focused work maintain near-perfect attention (U of Illinois, 2011). Learn optimal Pomodoro durations and variations for your work type.

iyda31 Mar 202616 min read