Guides
Plain-English explainers for the concepts behind the tools — what the numbers mean, which rate to compare, and the rules that trip people up. Each guide links straight to the Page & Bell tools that do the math for you.
Finance Calculators
APR vs. APY: Why the Same Rate Can Mean Two Different Things
APR ignores compounding; APY includes it. Learn which rate to compare for savings vs loans, and how compounding frequency changes what you earn or owe.
How Federal Income Tax Brackets Actually Work
Understand US federal tax brackets: why a raise never cuts your take-home pay, and how marginal and effective tax rates actually differ.
How US Sales Tax Works (and Why Your Total Varies by ZIP Code)
Why US sales tax has no single rate, how destination-based taxation and nexus work, and the difference between tax-inclusive and tax-exclusive pricing.
SEO & Marketing Tools
robots.txt vs. noindex vs. canonical: Controlling What Google Indexes
robots.txt controls crawling, noindex controls indexing, canonical consolidates duplicates. Learn which to use — and why blocking a page can keep it in Google.
Title Tags and Meta Descriptions: What Still Moves Clicks
Title tags affect ranking and clicks; meta descriptions affect only clicks. Both truncate by pixel width, not characters — here is how to write ones Google keeps.
What Is Schema Markup, and When Do Rich Results Actually Show?
Schema markup makes a page eligible — not guaranteed — for rich results. Learn JSON-LD, which types matter, and the review-snippet rule that trips people up.
Developer Utilities
Hashing vs. Encoding vs. Encryption (and When MD5 Is Fine)
Hashing is one-way, encoding is reversible, encryption needs a key. Learn which to use, why MD5 still has a place, and why passwords need more than SHA-256.
Linux File Permissions Explained: What 755 and 644 Actually Mean
Decode Linux file permissions and chmod numbers: read/write/execute, owner/group/other, and why 755 and 644 are the defaults you reach for.
Text Tools
How to Clean Up Text Pasted from AI, Word, and PDFs
Curly quotes, em dashes, non-breaking spaces, and hidden characters break code and search. Learn to spot and strip the junk that AI and Word leave behind.
Zero-Width and Invisible Characters: Why Your Text Breaks
Invisible characters like zero-width spaces and the BOM silently break search, code, and matching. Learn where they come from and how to strip them.
Converters
JSON vs. CSV vs. XML vs. YAML: Which Data Format to Use
CSV for tables, JSON for APIs, YAML for config, XML for documents. Learn each format's strengths and what gets lost when you convert between them.
px vs. rem vs. em: Which CSS Unit to Use and When
rem scales with the root, em with the parent, px is fixed. Learn which CSS unit to use for accessible, predictable sizing — and how to convert between them.
Business & HR Tools
Margin vs. Markup: The Difference That Quietly Costs You Money
Markup is over cost, margin is over price. Confusing them under-prices your products. See the formulas, a conversion table, and why 25% markup is only 20% margin.
Stripe vs. PayPal Fees: What You Actually Keep
Stripe and PayPal both run about 2.9% + 30¢ on card payments, but the fixed fee guts small transactions. See how fees really work and how to price around them.