Notes
How the tools are built and checked, and the occasional piece on the numbers behind them.
Converting a measurement does not make it more precise Ten miles is 16.09344 kilometres only if the ten was exact. Six digits out of two is a claim the original never made. Rounded numbers do not add up Six percentages that each round correctly can total 101. Somebody has to absorb the remainder, and the only real choice is who. Calories in and calories out are different measurements One side is computed from a table written in the 1890s, the other read off population averages. Subtracting them compounds both errors. Your photos know where you live Every phone photograph carries the coordinates it was taken at, to about a metre. Whether that travels with the file depends entirely on how you send it. Local storage is not a backup A browser notepad keeps your text without an account, which is the point. It also loses it to a cleared cache, a private window, or seven days of not visiting on iOS. DPI is not resolution Setting an image to 300 DPI adds no detail. It changes a note about how large to print the pixels you already have. A signature image is not a digital signature One is a picture of your name. The other binds a document to a certificate and detects any later change. Most forms want the first and some contracts require the second. Why your emoji is two characters long There are four ways to count the characters in a string, they disagree, and almost every text bug lives in the gap between them. Base64 images cost you caching Embedding an image saves one request and adds a third to its size. Under HTTP/2 that trade is worse than it used to be, and the cache loss is the part people forget. Email HTML is stuck in 1999 Outlook renders mail with Word. That single fact explains why email signatures are built from nested tables and inline styles, and why every modern layout technique fails. A word cloud shows frequency and nothing else It cannot tell you whether a word appeared in praise or complaint. Two decisions. A stop list and a square-root scale — are what separate a readable one from a decorative blob. A generated privacy policy is a draft A policy describing practices you do not follow is worse than having none; it is a false statement about your data handling, in writing, on your own site.
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