Guides

Short, practical explanations of the errors, formats and choices behind everyday developer tasks, each with a tool to try it right away.

How to Merge PDF Files Without Uploading Them Most online PDF mergers upload your documents to their servers. For contracts, bank statements and ID scans there are better options. Open Graph Tags: How to Control Link Previews When a link is shared on Facebook, LinkedIn, WhatsApp, Slack or X, a few lines in the page's head decide which title, text and picture people see. How to Scan a QR Code on a Laptop or PC A QR code on your own screen cannot be scanned with the phone in your hand if the phone is the screen, and a laptop has no camera app for it. Here are the ways that work. How to Type an API Response in TypeScript fetch gives you data typed as any, which switches TypeScript off exactly where bugs come from. Here is how to give API data a real type, quickly and safely. How to Turn an Elementor Page Into Plain HTML and CSS Elementor already sends the browser plain HTML and CSS; the job is to save that output, cut the CSS down to what the page uses, and replace the few parts that need WordPress. Base64 vs Base64URL: What Changes and When to Use Each Base64URL is standard Base64 with two characters replaced, - for + and _ for /, and usually without the = padding. Convert an Image to JPG: WebP, PNG and iPhone Photos JPG is the most widely accepted image format; here is when and how to turn any image into a real JPG without installing software and without uploading anything. Discord Timestamps: Syntax, Styles and Examples A Discord timestamp is a Unix time in seconds plus a style letter, and every reader sees it in their own time zone and locale. encodeURI vs encodeURIComponent: Which One to Use encodeURIComponent encodes 11 characters that encodeURI leaves alone, and those 11 characters decide whether a value stays inside its parameter. Invalid Base64 String: Why Decoding Fails and How to Fix It A Base64 decoder rejects a string for one of three reasons: a character outside the alphabet, a length that cannot be right, or padding in the wrong place. JSON Tutorial: Syntax, Rules and Working With JSON in JavaScript and Python JSON is the simplest and most widely used format for exchanging data; with a few short rules and two functions in each language, you can read, create and store any data. Unexpected Token in JSON: What It Means and How to Fix It This error means the text you tried to parse is not JSON. The token it names usually tells you exactly what you received instead. JWT vs Session Cookies: How They Differ and When to Use Each A session cookie is a key to state kept on the server; a JWT carries signed state to the server. That one difference drives every trade-off. How to Make a Free QR Code That Never Expires: Links, Wi-Fi and Location A QR code whose content is written directly into the code itself never expires; here is how to make one for each use and make sure it scans reliably. MD5 vs SHA-1 vs SHA-256: Which Hash Should You Use? Use SHA-256 for anything security-related; MD5 and SHA-1 are only acceptable where nobody gains anything by forging a matching hash. How to Reduce Image Size to 200 KB Without Visible Quality Loss Two things set the size of a photo, its dimensions and its compression quality; get those two right and a multi-megabyte phone photo shrinks in seconds to a size upload forms accept. Regex for Email Validation: A Practical Pattern and Its Limits No regex can tell you whether an address works. A short pattern catches typos; a confirmation email proves the rest. Regex for Numbers, Phone Numbers and IP Addresses Copy-ready patterns for numeric input, phone numbers and IP addresses, each tested, with notes on where a parser or library does the job better. What Is a Strong Password, and How Do You Create One That Is Really Secure? A password does not get its strength from looking complicated but from its length and randomness; this guide shows how to create one that is practically impossible to guess, without having to memorise it. Unexpected End of JSON Input: What It Means and How to Fix It The parser ran out of text before it found a complete value, and in most cases that is because there was no text at all. URL Encoding: How Percent-Encoding Works URL encoding replaces every byte that cannot appear as-is in a web address with a % sign followed by the value of that byte in hexadecimal. UUID vs GUID: What Is Actually Different GUID is Microsoft's name for a UUID. The differences you meet in practice are text formatting, byte order when the value is stored as 16 bytes, and SQL Server's sort order. UUID vs ULID vs Nano ID vs Auto-Increment IDs Five common ID schemes compared on what matters in practice: size, ordering, collision odds, database behaviour and what an ID gives away. WebP vs PNG vs JPG: Choosing the Right Image Format JPG is for photos that must open anywhere, PNG is for exact pixels, and WebP does both jobs in smaller files on the web.