Guides for people who
fix config at 2am.
Short, practical articles on JSON, YAML, TOML, JWTs, regex and the rest. Each one ends in a tool you can paste into.
# YAML → JSON yq -o=json config.yaml # JSON → YAML yq -P config.json
How to Verify a File Checksum (SHA-256, MD5)
Verify a file checksum in one command on macOS, Linux, or Windows. Compare the SHA-256 hash you compute against the one the site publishes.
Jul 7, 2026JWT Payload Best Practices — What to Put (and Not Put) in a Token
JWT payloads are readable by anyone who holds the token. Learn what belongs in the claims, what never does, and how to keep tokens small.
Jul 7, 2026What Does */15 * * * * Mean in Cron?
*/15 * * * * runs a cron job every 15 minutes. Learn how the step syntax works, when the job actually fires, and common variations.
Jul 7, 2026bcrypt vs SHA-256 for Storing Passwords
SHA-256 is fast — which makes it a bad choice for passwords. bcrypt is intentionally slow and built for authentication. Here's the difference and what to use.
Jun 22, 2026Regex Special Characters You Must Escape
Certain characters have special meaning in regex — use them literally and your pattern breaks silently. Here's the full list and how to escape them correctly.
Jun 22, 2026Trailing Commas in JSON: Why They Break Everything
JSON does not allow trailing commas — a single extra comma after the last item will throw a parse error. Here's why, and how to fix it fast.
Jun 22, 2026UTC vs Local Time for Timestamps: Which Should You Use?
Storing timestamps in UTC prevents timezone bugs and daylight-saving shifts. Learn when to use UTC vs local time and how to convert between them.
Jun 22, 2026Is a UUID Guaranteed to Be Unique?
UUIDs are designed to be unique without central coordination, but the guarantee depends on which version you use and how they're generated. Here's the real answer.
Jun 21, 2026JSON null vs Empty String vs Missing Key: What's the Difference?
null, \"\", and a missing key all mean something different in JSON. Here's when to use each one and how to handle them safely in your code.
Jun 21, 2026Which Characters Need URL Encoding?
Not every character needs to be percent-encoded in a URL. Here's exactly which characters are safe, which must be encoded, and where context matters.
Jun 21, 2026YAML Multiline Strings: Literal Block vs Folded Style
YAML has two multiline string styles — literal (|) and folded (>). Here's what each one does, when to use it, and how newlines are handled.
Jun 21, 2026Regex Flags Explained (g, i, m, s, u, y)
Regex flags change how a pattern matches. Learn what g, i, m, s, u, and y do, when to use each, and how to combine them for precise results.
Jun 20, 2026Unix Time in Seconds vs Milliseconds — How to Tell the Difference
Unix timestamps come in two flavors — seconds and milliseconds. Using the wrong one shifts dates by years. Here's how to spot which you have and convert correctly.
Jun 20, 2026UUID vs Auto-Increment IDs for Database Primary Keys
Choosing between UUIDs and auto-increment integers affects security, scalability, and performance. Here's when to use each and how UUID v7 changes the trade-off.
Jun 20, 2026What Is a JSON Lines File (JSONL)?
JSON Lines stores one JSON object per line — perfect for log files, streaming data, and large datasets that don't fit in memory. Here's how it works.
Jun 20, 2026How to Diff Two JSON Files
Compare JSON files to find added, removed, and changed keys. Use a diff tool, jq, or the command line — with practical examples for each approach.
Jun 19, 2026How to Generate a SHA-256 Hash in JavaScript
Use the Web Crypto API to compute SHA-256 hashes in the browser or Node.js — no libraries needed. Includes copy-paste code and async patterns.
Jun 19, 2026HS256 vs RS256: Which JWT Signing Algorithm Should You Use?
HS256 uses a shared secret while RS256 uses a public/private key pair. Here's when to pick each and why it matters for your JWT security model.
Jun 19, 2026Regex Lookahead and Lookbehind Explained
Lookaheads and lookbehinds let you match a pattern only when it's preceded or followed by something else — without including that context in the match.
Jun 19, 2026Are JWTs Encrypted? Signed vs Encrypted Tokens
Most JWTs are signed, not encrypted — anyone can read the payload. Learn the difference between JWS and JWE, and when to use each.
Jun 18, 2026Common Cron Examples You Can Copy Right Now
Ready-to-use cron schedules for every 5 minutes, hourly, daily, weekly, and monthly jobs — with plain-English explanations for each.
Jun 18, 2026How to Escape Special Characters in JSON Strings
JSON strings require backslash escapes for quotes, backslashes, newlines, and control characters. Here's every escape sequence you need.
Jun 18, 2026What Is a Checksum and How Do You Verify One?
A checksum is a hash that proves a file wasn't corrupted or tampered with. Learn how checksums work and how to verify them in minutes.
Jun 18, 2026JWT Expiration and Refresh Tokens Explained
Learn how JWT expiration works with the exp claim, why short-lived tokens need refresh tokens, and the patterns used in real auth systems.
Jun 15, 2026ULID vs UUID — Which Should You Use?
ULIDs are sortable, URL-safe unique IDs that solve UUID's randomness problem. Compare ULID vs UUID on format, sortability, and database performance.
Jun 15, 2026URL Encoding Spaces: %20 vs +
Both %20 and + represent spaces in URLs, but they aren't interchangeable. Learn which to use in query strings vs paths and why mixing them breaks things.
Jun 15, 2026What Is a Salt in Password Hashing?
A salt is random data added to a password before hashing, preventing rainbow table attacks. Learn how it works and why every password needs one.
Jun 15, 2026Base64 URL-Safe Encoding Explained
Standard Base64 breaks in URLs because of + / and =. URL-safe Base64 fixes it. Learn the differences, where it is used (JWT), and how to convert.
Jun 11, 2026Common Regex Patterns: Email, URL, Phone & More
Copy-paste regular expressions for email, URL, phone, IP address, hex color, and more — with explanations and a free regex tester to validate them.
Jun 11, 2026encodeURIComponent vs encodeURI: What's the Difference?
encodeURIComponent and encodeURI both percent-encode, but they protect different characters. Learn which to use for query parameters versus full URLs.
Jun 11, 2026Epoch Time Explained (and the Year 2038 Problem)
Epoch time is the foundation of how computers track time. Learn what the Unix epoch is, why 1970 was chosen, and the looming Year 2038 problem.
Jun 11, 2026How to Base64 Encode and Decode in JavaScript
Encode and decode Base64 in JavaScript the right way — btoa, atob, and the UTF-8-safe approach with TextEncoder. Plus Node.js Buffer examples.
Jun 11, 2026How to Compare Two Text Files (Diff)
Comparing two versions of text or code is a daily task. Learn how diffs work, what added and removed lines mean, and how to compare text online.
Jun 11, 2026How to Convert a Unix Timestamp to a Date
Convert a Unix timestamp to a human-readable date in JavaScript, Python, SQL, and online — plus the seconds-vs-milliseconds gotcha.
Jun 11, 2026How to Convert CSV to JSON
Convert spreadsheet CSV into a JSON array of objects — how headers become keys, parsing pitfalls with quotes and commas, and a free CSV to JSON tool.
Jun 11, 2026How to Convert JSON to CSV
Turn a JSON array of objects into CSV for spreadsheets — how the mapping works, handling nested fields and commas, and a free online JSON to CSV tool.
Jun 11, 2026How to Convert JSON to XML
Convert JSON to XML and back — how objects map to elements, how arrays and attributes are handled, and a free online JSON to XML converter.
Jun 11, 2026How to Create and Sign a JWT
Create a JSON Web Token step by step — build the header and claims, sign with HS256, and produce a token. With code and a free online JWT generator.
Jun 11, 2026How to Decode a JWT
Decode a JSON Web Token to read its header and payload — online, in JavaScript, and on the command line. Plus why decoding is not the same as verifying.
Jun 11, 2026How to Decode Base64 Online (and in Code)
Decode Base64 back to text or binary — online instantly, or in JavaScript, Python, and the command line. With UTF-8 gotchas and a free decoder tool.
Jun 11, 2026How to Fix Common YAML Errors (Indentation, Tabs, and More)
The most common YAML errors explained in plain English — bad indentation, tab characters, unquoted special characters, and duplicate keys — with copy-paste fixes for each.
Jun 11, 2026How to Flatten Nested JSON for CSV Export
CSV is flat but JSON nests. Learn strategies to flatten nested objects and arrays into columns so your data exports cleanly to a spreadsheet.
Jun 11, 2026How to Generate a UUID in JavaScript
Generate UUIDs in JavaScript the modern way with crypto.randomUUID, plus Node.js options and why you should avoid Math.random for IDs.
Jun 11, 2026How to Read a Cron Expression
Cron expressions schedule recurring jobs with five fields. Learn what each field means, how to read the symbols, and common examples explained.
Jun 11, 2026How to Verify a JWT Signature
Verifying a JWT signature is what makes it trustworthy. Learn how HS256 and RS256 verification works, what claims to check, and how to validate a token.
Jun 11, 2026ISO 8601 Date Format Explained
ISO 8601 explained — the standard date and time format like 2026-06-11T14:30:00Z, what each part means, timezone offsets, and why it sorts correctly.
Jun 11, 2026JSON vs XML: Which Should You Use?
JSON and XML both structure data, but JSON is lighter and XML is more expressive. Compare syntax, size, features, and ideal use cases.
Jun 11, 2026JSON vs YAML vs TOML: Which Config Format Should You Use?
A practical, no-fluff comparison of JSON, YAML, and TOML for configuration files — with real examples, gotchas, and a clear recommendation for each use case.
Jun 11, 2026JWT vs Session Cookies: Which Should You Use?
JWTs and server sessions both handle auth, but differently. Compare statelessness, revocation, security, and scaling to choose the right approach.
Jun 11, 2026MD5 vs SHA-256: What's the Difference?
MD5 and SHA-256 are both hash functions, but only one is secure. Compare speed, output size, collision resistance, and when each is appropriate.
Jun 11, 2026Regex Cheat Sheet for Beginners
A concise regular expression cheat sheet — character classes, quantifiers, anchors, groups, and flags — with examples and a free regex tester.
Jun 11, 2026Regex Greedy vs Lazy Quantifiers: What's the Difference?
Greedy vs lazy regex quantifiers explained — why .* matches too much, how adding ? makes it lazy, and when to use each with clear examples.
Jun 11, 2026SHA-1 vs SHA-256: What's the Difference?
SHA-1 vs SHA-256 compared — digest size, security, collision attacks, and why SHA-1 is deprecated and you should use SHA-256 for new work.
Jun 11, 2026Understanding JSON Syntax Errors and How to Fix Them
JSON is strict, and its error messages are cryptic. Here are the most common JSON syntax errors — trailing commas, single quotes, missing commas, comments — and exactly how to fix each.
Jun 11, 2026UUID Versions Explained: v1, v4, and v7
Not all UUIDs are the same. Compare UUID v1 (time + MAC), v4 (random), and v7 (time-ordered) and learn which version to use for your case.
Jun 11, 2026What Are JWT Claims? iss, sub, aud, exp, and More
Understand JWT claims — the registered claims iss, sub, aud, exp, iat, nbf, plus public and private claims — and what each one means in a token's payload.
Jun 11, 2026What Is a Hash Function?
Hash functions turn any input into a fixed-size fingerprint. Learn what they are, key properties, common algorithms, and what they're used for.
Jun 11, 2026What Is a JWT (JSON Web Token)? A Complete Guide
JWT explained simply — the three parts of a token, how signing works, what claims are, and when to use JSON Web Tokens. With a free decoder.
Jun 11, 2026What Is a Unix Timestamp?
A Unix timestamp counts seconds since 1970. Learn what it is, why it's used everywhere, how it handles time zones, and the Year 2038 problem.
Jun 11, 2026What Is a UUID and How Does It Work?
UUIDs are 128-bit unique identifiers used everywhere in software. Learn what they are, how uniqueness works, their format, and when to use them.
Jun 11, 2026What Is Base64 Encoding and How Does It Work?
Base64 explained in plain English — what it is, why it exists, how the encoding works step by step, and when to use it. With examples and a free online tool.
Jun 11, 2026What Is URL Encoding (Percent-Encoding)?
URL encoding explained — why spaces become %20, which characters must be encoded, and how percent-encoding keeps URLs valid. With a free online tool.
Jun 11, 2026When and How to URL-Encode Query Parameters
A practical guide to encoding query string parameters — which characters break URLs, how to build query strings safely, and using URLSearchParams.
Jun 11, 2026Why You Should Never Use MD5 for Passwords
MD5 (and even plain SHA-256) are the wrong tools for password storage. Learn why fast hashes are dangerous and what to use instead — bcrypt, argon2.
Jun 11, 2026How to Convert JSON to YAML (and Back) Online
A step-by-step guide to converting JSON to YAML and YAML to JSON — what changes, common pitfalls with quotes and types, and how to do it instantly online.
Jun 10, 2026How to Convert JSON to TOML (and TOML to JSON)
Convert JSON to TOML and back the right way. Learn how nested objects become TOML tables, how arrays of objects map, and the gotchas to avoid.
Jun 9, 2026What Is a TOML File? A Beginner's Guide
TOML explained for beginners — what it is, why projects like Cargo and pyproject use it, its syntax for tables and arrays, and how it compares to JSON and YAML.
Jun 8, 2026How to Format and Prettify JSON
Learn how to format, prettify, and beautify JSON — why indentation matters, 2 vs 4 spaces, and how to clean up minified JSON instantly online.
Jun 7, 2026YAML Anchors and Aliases Explained
YAML anchors (&) and aliases (*) let you reuse blocks and keep config DRY. Learn the syntax, merge keys, and when to use them with practical examples.
Jun 6, 2026How to Comment in JSON (and Why You Can't)
JSON does not support comments — here is why, plus five practical workarounds including JSONC, JSON5, comment keys, and switching to YAML or TOML.
Jun 5, 2026Kubernetes YAML: Common Mistakes and How to Avoid Them
The most common Kubernetes YAML mistakes — indentation, wrong types, string booleans, missing quotes on numbers — and how to catch them before kubectl apply.
Jun 4, 2026JSON vs JSON5 vs JSONC: What's the Difference?
JSON, JSON5, and JSONC compared — what each allows (comments, trailing commas, unquoted keys), where they are supported, and which to use for config.
Jun 3, 2026How to Minify JSON (and When You Should)
Minifying JSON strips whitespace to shrink payloads. Learn what minification does, how much it saves, when to use it versus gzip, and how to do it online.
Jun 2, 2026JSON Schema Validation: A Practical Guide
Learn what JSON Schema is, how to write one, and how to validate JSON against it — with examples of types, required fields, and nested objects.
Jun 1, 2026