Developer guides
The formats, edge cases and gotchas behind the tools — Base64, timestamps, JSON escaping and getting data out of API responses.
Private Online Tools for Everyday Tasks: What Happens to Your Files?
What really happens to your photos, documents and numbers when you use a free online tool, how to tell a tool that uploads from one that works on your device, and which everyday jobs never need a server at all.
Percentage Points vs Percent — and Five Other Percentage Traps
Why a rate going from 4% to 5% is a 25% rise, why +10% then −10% loses money, how to take VAT off properly, and why 30% plus 20% off is not 50% — six everyday percentage mistakes with worked examples.
How to Compress Images Without Losing Visible Quality
Why resizing beats the quality slider, which quality settings are safe, when WebP or PNG is the right format, and how to get a photo under a file-size limit without guessing.
How Long Should a Password Be? Entropy, Passphrases and Crack Times
What password entropy actually measures, how many bits you need, why a six-word passphrase beats P@ssw0rd!, and why the hash a website uses matters as much as the password you pick.
Loan Overpayments: How Much Interest Do They Really Save?
Worked examples of what extra monthly payments and lump sums actually save on a car loan and a mortgage, why early overpayments are worth far more, and the rate detail that quietly changes every answer.
Browser-Based Developer Tools: Why Client-Side Beats Uploading
Why client-side developer tools are usually the right default, what actually happens to data you paste into an online utility, and how to tell the two kinds apart before you paste anything sensitive.
Converting CSV to JSON Without Breaking Your Data: 7 Gotchas
Leading zeros that vanish, order IDs that get rounded, semicolons from European Excel and line breaks inside cells — seven ways a CSV to JSON conversion quietly corrupts data, and how to avoid each one.
UUID v4 vs UUID v7: Which One Should Be Your Primary Key?
Random v4 UUIDs scatter inserts across your index; time-ordered v7 UUIDs append to the end of it. How each is built, what v7 leaks, where it does not sort, and a simple rule for choosing.
From Copy as cURL to Production Code, Without the Copied Secrets
Turning a Copy as cURL command from DevTools into clean client code — how each flag maps onto fetch, Axios, requests, httpx and net/http, and how to avoid committing the credentials that came along for the ride.
Debugging JWTs Client-Side: Header, Claims, Expiry and Privacy
What is actually inside a JSON Web Token, why pasting a live one into an online decoder hands over a working credential, and how to read the claims that explain most authentication failures.
Extracting and Cleaning URLs from Large API Responses, Safely
Pulling every link out of a large REST, GraphQL or Postman response without pasting proprietary data into a server-side parser — including the escaping, filtering and edge cases that make the job fiddly.
Base64 Encoding Explained (and the Mistake Everyone Makes)
What Base64 actually does, why it makes data roughly a third larger, the difference between standard and URL-safe alphabets, and the one mistake that causes most Base64 bugs in production.
Unix Timestamps: Seconds, Milliseconds and the 2038 Problem
How Unix time works, how to tell seconds from milliseconds at a glance, why leap seconds make it not-quite-elapsed-time, and what the year 2038 problem actually breaks.
How to Extract All URLs from an API Response
A no-code workflow to extract every image, video and link URL from REST, GraphQL, Postman and Insomnia responses, then filter, dedupe and export the list without writing a throwaway script.
Why JSON URLs Contain Backslashes (and How to Fix Them)
Learn why URLs in JSON and API responses show up as https:\/\/example.com, why the escaping is valid rather than a bug, and how to unescape them instantly without writing a regex.