Guides
Practical knowledge behind our tools: short, clear and actionable guides. Each one ends with a quick link to the related tool.
CSV encoding problems in Excel
When a CSV file shows broken letters in Excel, encoding is the cause. Why it happens, three ways to fix it and what a BOM does.
Reducing image size: JPG vs PNG vs WebP
Which image format to pick, how large an image really needs to be, and how to shrink a file without visible quality loss. A short, practical guide.
What is a JWT?
A JWT (JSON Web Token) has three parts. What is inside, what the signature does, how to read exp and the common security mistakes.
How to calculate VAT
Formulas for adding VAT and for removing it from a gross price, with examples and rounding. The common mistake: taking the rate of the gross amount.
What is Base64?
Base64 is an encoding that turns binary data into text. How it works, why it adds 33%, where it is used and why it is not encryption.
How to create a QR code
What to watch for when creating a QR code: error correction level, size, color, printing and testing before you publish. Examples for Wi-Fi, WhatsApp and contact cards.
File naming best practices
Practical rules for spaces, dates, sequence numbers and special characters in file names, with examples of bulk renaming.
Percentage calculation guide
Finding a percentage, percentage increase and decrease, discount math and the difference between percent and percentage points. The four basic formulas with examples.
How loan payments are calculated
The equal-payment (annuity) loan formula, a worked example, the difference between monthly and annual rates and why a lender's offer can differ.
What is JSON and common errors
The rules of the JSON format, common mistakes (trailing commas, single quotes, comments) and what to watch for with large numbers.