Guides
The explanations behind the tools: what each one is actually doing, when to use it, and where it stops being the right answer. Every guide is grounded in the code that runs the tool, checked by hand, and signed.
Latest
How to Merge, Split and Rotate PDFs Without Uploading Them
A practical walkthrough of combining, splitting and fixing PDFs entirely in your browser, what pdf-lib can and cannot do, and where the limits are.
Sep 3, 2026Generators guidePassword Length vs Complexity: The Entropy Math, Worked Out
Why a longer password beats a cleverer one, with the entropy formula, a table of real numbers, and what the strength meter on the generator is measuring.
Sep 3, 2026Generators guideQR Codes Explained: Error Correction, Size and Why SVG Beats PNG
What the L, M, Q and H settings do, how much damage a code can survive, how big to print one, and when to export SVG instead of PNG.
Sep 3, 2026Generators
Password Length vs Complexity: The Entropy Math, Worked Out
Why a longer password beats a cleverer one, with the entropy formula, a table of real numbers, and what the strength meter on the generator is measuring.
Sep 3, 2026Generators guideQR Codes Explained: Error Correction, Size and Why SVG Beats PNG
What the L, M, Q and H settings do, how much damage a code can survive, how big to print one, and when to export SVG instead of PNG.
Sep 3, 2026Generators guideHow Fair Random Picks Work: Wheels, Name Draws and Dice
Why Math.random is not enough, what rejection sampling and a Fisher-Yates shuffle fix, and how to run a draw that nobody can dispute.
Sep 3, 2026Images
JPEG vs PNG vs WebP: Which Format to Use, With Real File Sizes
The honest tradeoffs between the three formats every browser understands, measured on the same image, and a simple rule for choosing.
Sep 3, 2026Images guideHow to Shrink an Image for the Web or Email Without Wrecking It
Resize first, then compress: the order matters. Target sizes for email, web pages and social uploads, with measured results from the compressor.
Sep 3, 2026Developer
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How these are written
Each guide starts from the source code of the tool it covers, so the numbers and behaviors it describes are the ones you will actually see on the page, not a generic description. Worked examples are run through the real tool and screenshotted. Claims about standards link to the standard. When a tool has a limit, the guide says so rather than glossing over it. If you spot a mistake, the contact page reaches Nathan directly and corrections are dated on the page.