What a UUID is, and which version you actually want
128 bits, five fields, 32 hex digits, and a version nibble that decides how much of it is random. Here is the collision arithmetic and how to pick a version.
Blog
Notes from the bench
Longer writing about the things these tools do — how a format decides its own quality, what the numbers in a contrast ratio mean, why two of them disagree about the same file. Everything here is written to answer a question you arrived with, and every piece ends at the tool that does the job.
Verifying a download without trusting the page you got it from
A checksum proves your file arrived byte-for-byte intact. It proves nothing at all if the digest was published by the page that served the file.
What password strength meters actually measure
Every meter on the web is estimating the same quantity, and most of them estimate it badly. Here is the arithmetic behind the bar, why two meters disagree, and which lever still moves it.
JPEG, PNG, WebP or AVIF: choosing an image format you will not regret
Most format choices are made out of habit and paid for later. The order of the questions settles nearly all of them, and one of the answers is a hard no.
Are passphrases actually stronger than passwords?
Four words can beat twelve random characters, and four words can also be worth five hours of guessing. The difference is not the spaces — it is where the words came from.
Compressing an image without visible damage
You cannot pick a quality setting from a table — the number only means something inside one encoder. What you can do is learn what damage looks like and where to look for it.
Which hash to use, and what each one is for
MD5 is broken and still the right choice for some jobs. SHA-256 is not the right choice for storing passwords. Here is the line between them, and the digest sizes to match.
Resize or compress first? The order changes the result
A downscale is an average, and averaging pixels that already carry compression error bakes that error in. Here is the arithmetic of a five-to-one reduction, and when the other order wins.
Every favicon size, and what each one is for
One favicon.ico cannot serve a browser tab, a Windows shortcut and an iPhone home screen, so here is every size that can.
Why a resized PNG sometimes comes out bigger
Shrinking a PNG removes pixels, so the file should shrink with them. When it grows instead, the pixel format changed underneath, and the arithmetic explains why.
EXIF orientation, and the photo that shows up sideways
A photograph can be upright in one program and sideways in the next, because the uprightness is not in the pixels but in a note that gets thrown away.
Contrast ratios, and how to read one without doing the maths
The part everyone skips is the linearisation inside the formula. Here is the whole calculation for one grey on white, and what the number cannot see.
Fixing a brand colour that fails contrast
The brand hex is fixed, so something else has to move. Here is the order I try the alternatives in, the arithmetic behind darkening a fill, and where each one breaks.
RGB, HSL and OKLCH: three ways to name a colour
Hex and rgb() are one model in two spellings. The useful question is which notation to reach for when you are changing a colour rather than copying one.
Building a palette from a single colour
Generators hand you colours of equal lightness, which is why the result looks like a chart. A usable interface palette is a ramp, one loud accent, and greys that are not quite grey.
Gradients that do not band
An 8-bit channel holds 256 values, a dark ramp spends them faster than a light one, and the fix is more contrast, a little noise, or a shorter ramp.
Reading a JSON syntax error instead of guessing at it
A parse error carries a line, a column and a character offset, and almost nobody reads them. What each standard JSON message means, with a real broken document for every one.
JSON to CSV without breaking Excel
Turning an object into rows takes four lines of code. Keeping the customer number 007 and the accented surname intact is the part that decides whether the file is usable.
What Base64 is actually for
Base64 is neither encryption nor compression: it is the adapter that carries arbitrary bytes through a text-only channel, and it makes them larger.
Reading a URL query string without guessing
A query string is key=value pairs joined by ampersands, and every value is percent-encoded. Here is how to decode one and read it without guessing.
Comparing two documents, and why the diff looks wrong
A diff that marks a whole paragraph when you swapped one word is not broken. It compares lines, and prose is not made of lines. Here is the mechanism, and the fixes.
Why your word count disagrees with theirs
Two honest counters can differ by a few percent on the same text, and the cause is a hyphen, a dash or an apostrophe rather than a mistake in either tool.
Picking a naming convention, and living with it
The separator you choose matters less than the constraints it has to survive. Where each convention belongs, and what breaks when a project mixes them.
The tools themselves Every article here is written around something on the bench. If you would rather use one than read about it, the full list is one click away.
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