Guides

Articles to help you understand the tools more deeply and choose the right one.

Regular Expression Cheat Sheet — Metacharacters and Patterns (2026)
A quick reference for regex metacharacters, quantifiers, and anchors, plus ready-to-use patterns for email, URL, and dates with caveats. Links to an in-browser tester.
Why CSV Files Show Garbled Text in Excel, and How to Fix It (UTF-8, Shift_JIS, BOM)
A clear explanation of the classic "CSV opens garbled in Excel" problem from a character-encoding angle — the relationship between UTF-8, Shift_JIS, and the BOM, plus fixes and prevention.
Splitting and Settling Bills for Trips and Parties — Fronting, Rounding, Fairness
Splitting a bill is more than "total ÷ people." Here is how to settle fairly in real situations: money fronted by one person, different attendees each day, non-drinkers, and how to handle remainders.
What Is Base64? How It Works, When to Use It, and Pitfalls
A friendly explanation of Base64: why it grows data by about 33%, what the trailing = means, how it differs from encryption, and the URL-safe variant.
How to Choose a QR Code Error-Correction Level (L/M/Q/H)
Understand the L, M, Q, and H error-correction levels and how to choose. Recommendations by use case: on-screen, print, outdoor signage, and logo overlays.
How to Create a Strong Password — Length, Character Sets, Entropy
Learn what makes a password hard to guess, starting from entropy (bits). Does length or character variety matter more? Plus the danger of reuse and tips for managing them.
JSON Format vs. Minify: The Difference and When to Use Each
Understand JSON pretty-printing vs. minifying: when to use each, whether the data changes, and the common causes of parse errors.
PNG vs. JPEG vs. WebP: The Differences and How to Choose
Understand PNG, JPEG, and WebP: lossless vs. lossy, transparency, photos vs. graphics, and which format to pick.
Counting Characters — Bytes vs. Code Points vs. Graphemes
The "character count" depends on how you count. Learn the difference between bytes, code points, and graphemes (the visible character), and why emoji and non-English text throw the numbers off.
What Is a UUID? How v4 Works and When to Use It
Understand UUID v4: why collisions are effectively impossible, the 8-4-4-4-12 format, how it differs from sequential IDs, and when to use it.
How to Write a Cron Expression — Reading the 5 Fields
Learn to write cron expressions: what the five fields mean, the * and */ symbols, and the surprising behavior when day-of-month and day-of-week are both set.
Why You Should Strip Exif (Location, etc.) From Images
Learn what Exif is: the metadata embedded in photos — including GPS location and timestamps — its privacy risks, and why you should remove it before sharing.