JWT Security Best Practices Every Backend Developer Should Follow
Common JWT pitfalls per RFC 7519 including algorithm confusion, expiry handling, and key rotation.
Read article →The HT99 Tools Blog
Original, in-depth explainers that complement our tools — covering the why and when, not just the how. Every article is dated, sourced, and reviewed regularly.
Latest Articles
Pregnancy Weight Gain: What's Normal and What's Not
Trimester-by-trimester guide based on IOM 2009 recommendations and pre-pregnancy BMI.
Read article →Secure Password Best Practices for End Users and Developers
NIST 800-63B guidance, length vs complexity, entropy, and proper password storage.
Read article →APR vs APY: The Critical Difference That Costs You Money
Why the same interest rate can produce very different real costs or returns — per Truth in Lending Act.
Read article →Body Fat Measurement Methods Compared: Which Is Most Accurate?
Navy method, calipers, DEXA, bioimpedance — accuracy, cost, and practicality compared.
Read article →WCAG Color Contrast Explained: Making the Web Accessible
What the WCAG 2.2 ratios mean per the W3C spec, how to test them, and easy fixes for failing designs.
Read article →Hashing vs Encryption: What Every Developer Must Know
Why these are different problems with different solutions — and the dangers of confusing them.
Read article →Retirement Savings Milestones by Age: Are You on Track?
The benchmark numbers you should hit at 30, 40, 50, and 60 to retire comfortably.
Read article →Mean, Median, Mode: Choosing the Right Average for Decisions
When each measure of central tendency is most useful, with worked examples.
Read article →Browse by Category
Finance (7 articles)
9 min · Jan 2025
How Loan Amortization Works: A Complete Beginner's Guide
Understand the math behind loan amortization with the standard annuity formula, see real payment schedules, and learn how extra payments save thousands.
8 min · Feb 2025
Fixed vs Variable Interest Rates: Which Is Better in 2025?
Compare fixed and variable rate loans with real numbers, pros, cons, and a decision framework.
10 min · Feb 2025
Compound Interest Explained: The Eighth Wonder of the World
See why Einstein supposedly called compound interest the eighth wonder — with worked examples and the Rule of 72.
11 min · Mar 2025
How Much House Can I Afford? The 28/36 Rule Explained
Learn the gold-standard rule for housing affordability with step-by-step budget math.
9 min · Mar 2025
Avalanche vs Snowball: Best Credit Card Payoff Strategies
Compare the two most popular debt payoff methods with real timelines and interest saved.
12 min · Apr 2025
Retirement Savings Milestones by Age: Are You on Track?
The benchmark numbers you should hit at 30, 40, 50, and 60 to retire comfortably.
7 min · Apr 2025
APR vs APY: The Critical Difference That Costs You Money
Why the same interest rate can produce very different real costs or returns — per Truth in Lending Act.
Health & Fitness (7 articles)
8 min · Jan 2025
Why BMI Alone Is Misleading: A Healthier Way to Track Fitness
The science behind BMI limitations per CDC and WHO, and what metrics give a fuller health picture.
10 min · Feb 2025
How Many Calories Do I Really Need? TDEE Science Explained
The complete guide to calculating maintenance calories using the Mifflin-St Jeor formula and activity multipliers.
11 min · Feb 2025
Macros 101: How to Calculate Protein, Carbs and Fat for Your Goals
A practical formula-based approach to setting macronutrient targets with Atwater energy values.
7 min · Mar 2025
8 Glasses a Day and Other Water Intake Myths Debunked
The real science behind hydration needs per IOM/National Academies, and how to actually measure them.
9 min · Apr 2025
Heart Rate Training Zones: Train Smarter, Not Harder
How to use target heart rate zones with the Karvonen formula and AHA thresholds to optimize cardio.
10 min · Apr 2025
Body Fat Measurement Methods Compared: Which Is Most Accurate?
Navy method, calipers, DEXA, bioimpedance — accuracy, cost, and practicality compared.
8 min · May 2025
Pregnancy Weight Gain: What's Normal and What's Not
Trimester-by-trimester guide based on IOM 2009 recommendations and pre-pregnancy BMI.
Mathematics (4 articles)
7 min · Jan 2025
10 Percentage Math Tricks That Save Time Every Day
Practical mental-math shortcuts for tips, discounts, taxes, and growth rates.
9 min · Feb 2025
Standard Deviation Explained Simply with Real Examples
What standard deviation actually tells you, why Bessel's correction matters, and why it shows up in real life.
8 min · Mar 2025
Where Quadratic Equations Show Up in Real Life
From projectile motion to profit maximization — practical applications of quadratics with completing-the-square derivation.
8 min · Apr 2025
Mean, Median, Mode: Choosing the Right Average for Decisions
When each measure of central tendency is most useful, with worked examples.
Developer (6 articles)
10 min · Jan 2025
Understanding JSON: A Practical Guide for Developers
RFC 8259 syntax, validation, common pitfalls, and best practices for working with JSON.
8 min · Feb 2025
How Base64 Encoding Works and When to Use It
The mechanics of Base64 per RFC 4648, common use cases, and when you should NOT use it.
12 min · Mar 2025
Regex Mastery: A Practical Cheat Sheet with Real Examples
The patterns every developer should memorize, plus common regex anti-patterns.
9 min · Apr 2025
Hashing vs Encryption: What Every Developer Must Know
Why these are different problems with different solutions — and the dangers of confusing them.
10 min · May 2025
Secure Password Best Practices for End Users and Developers
NIST 800-63B guidance, length vs complexity, entropy, and proper password storage.
11 min · May 2025
JWT Security Best Practices Every Backend Developer Should Follow
Common JWT pitfalls per RFC 7519 including algorithm confusion, expiry handling, and key rotation.
Text & SEO (3 articles)
8 min · Jan 2025
Keyword Density in 2025: Does It Still Matter for SEO?
The truth about keyword density after Google's helpful content updates.
9 min · Feb 2025
How Readability Affects SEO Rankings: A Data-Backed Guide
Real correlation between Flesch Reading Ease scores, dwell time, and rankings.
6 min · Mar 2025
Writing Perfect URL Slugs for SEO and UX
Concrete rules for crafting slugs that rank well and read cleanly.
Time & Productivity (2 articles)
7 min · Jan 2025
Business Days vs Calendar Days: Why It Matters in Contracts
Avoid expensive contract misunderstandings by understanding business-day counting.
10 min · Mar 2025
Time Zones in Software: Best Practices for Global Apps
Store UTC, display local — and other rules that prevent scheduling disasters.
Design (2 articles)
11 min · Feb 2025
Color Theory for UI Design: A Practical Primer
The 60-30-10 rule, color harmony, and avoiding the most common UI color mistakes.
8 min · Apr 2025
WCAG Color Contrast Explained: Making the Web Accessible
What the WCAG 2.2 ratios mean per the W3C spec, how to test them, and easy fixes for failing designs.