ULID vs UUID: Sortable IDs for Database Keys
ULID vs UUID for database keys: why time-ordered IDs improve index performance, how ULIDs encode time and how they compare with UUID v4 and v7.
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Guides on test data, international formats, privacy, passwords and probability.
MongoDB ObjectId Structure Explained Byte by Byte
MongoDB ObjectId structure explained: what the timestamp, random value and counter bytes mean, how to read creation dates and when to use your own _id.
How Ethereum Addresses Work: Format, Checksum, Safety
How Ethereum addresses work: where the 0x and 40 hex characters come from, what the EIP-55 checksum does and how to test wallet inputs safely.
IPv6 Address Notation Explained: Rules and Ranges
IPv6 address notation explained: how to shorten addresses with ::, which prefixes mean link-local, private or documentation, and how to test parsers.
How IBAN Check Digits Are Calculated, Step by Step
Learn how IBAN check digits are calculated with the mod-97 method, how to validate an IBAN in code and how to test payment forms with safe sample data.
ABA Routing Number Checksum Explained for Developers
ABA routing numbers explained: what each of the nine digits means, how the 3-7-1 checksum works and how to validate ACH and payroll forms in your code.
How to Decode a VIN: What All 17 Characters Mean
How to decode a VIN: what the manufacturer code, model year letter, plant code and check digit mean, plus a quick way to verify a VIN by hand.
ISBN-13 Check Digit Explained, With Worked Examples
ISBN-13 check digits explained with worked examples: what each part of a book number means, how to convert ISBN-10 to ISBN-13 and how to validate both.
EAN vs UPC Barcodes: Differences Explained Simply
EAN vs UPC barcodes explained: how EAN-13, UPC-A and EAN-8 differ, what the prefix really means and how the check digit is calculated, with examples.
License Plate Formats Around the World, Explained
License plate formats around the world explained: how plates in the UK, Germany, France, Italy, Spain, India and Brazil are built, plus fun plate games.
Random Decimals Explained: Precision and Rounding
Random decimals explained: how they are generated, why 0.1 + 0.2 is not 0.3 in code, how to round correctly and practical uses in tests and simulations.
Fun Fraction Practice Activities for the Classroom
Fun fraction practice activities for kids: comparing, simplifying, number lines and decimal conversion games you can run in minutes with random fractions.
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