GUIDES

Background for the work between the tools.

Practical explanations of the formats and problems the tools handle, with worked examples and the mistakes to avoid. Every guide links to the related tools so you can act on it immediately.

PDF

Merge, split, and reorder PDFs without uploading themHow local browser PDF editing works, when to split or extract pages, and what document features are not preserved.

Images

JPG, PNG, or WebP: choosing the right image formatHow the three common web image formats differ, which one to export, and when converting between them helps or hurts.Resizing and compressing images for the webA four-step routine that cuts photo sizes by over 90% without visible loss, with target dimensions for common uses.Photo metadata: what EXIF and GPS reveal and how to remove itWhat photos store about where and how they were taken, which channels keep it, and how to share a clean copy.

CSV & tables

Cleaning messy CSV data in the browserA practical pass over duplicate rows, filters, sorting, column selection, and CSV to JSON conversion.

JSON

JSON validation, formatting, and JSON LinesWhat a validator actually checks, why formatting is safe, and when JSON Lines is the right shape for your data.Comparing and merging JSON documentsWhy text diffs fail on JSON, how structural comparison and key sorting help, and how merge strategies treat objects and arrays.

Developer utilities

Base64, URL encoding, and HTML entities explainedThree encodings that are constantly confused, what each one is for, and the mistakes that cause broken data.Reading JWTs: what decoding shows and what it cannot proveThe three parts of a JSON Web Token, the claims that matter when debugging logins, and why decoding is never verification.

DevOps

What a Content-Security-Policy header actually doesHow directives and fallbacks resolve, why a policy does not fix injection by itself, and how to roll one out safely.Cron expressions: reading and building schedulesThe five fields, the day-of-month and day-of-week quirk, and how to check a schedule before it runs in production.

Text

Text cleanup: whitespace, duplicates, and invisible charactersWhy two identical-looking strings fail to match, and the safe order of operations for cleaning a list.

APIs & HTTP

Converting cURL to fetch and Python requestsHow cURL flags map to fetch and requests, why browser requests fail where cURL works, and how to share requests without leaking tokens.Verifying webhook signatures with HMACHow webhook signing works, the four reasons valid events fail verification, and how to check signatures safely in production.

Small business

Pricing with margin, markup, and break-evenWorked examples of margin vs. markup, break-even volume, and freelance hourly rates, with the mistakes that quietly cost money.How loan payments work: amortization explainedThe formula behind a fixed monthly payment, how to read an amortization schedule, and what longer terms and higher rates really cost.

Calculators

Percentages without mistakesPercentage change, reversing percentages, points vs. percent, and the other traps behind misleading numbers.

Code tools

Regular expressions: a practical guideThe building blocks of regex, working from examples, capture-group replacements, and the backtracking trap that freezes programs.Semantic versioning and dependency rangesWhat MAJOR.MINOR.PATCH promises, how ^, ~, x, and hyphen ranges resolve, and how lockfiles fit in.

Configuration

YAML, TOML, INI, XML, and JSON: converting configuration safelyHow the common configuration formats differ in types and structure, and how to convert between them without silent changes.

Dates & time

Time zones, daylight saving, and Unix timestampsInstants vs. wall-clock times, seconds vs. milliseconds, and how DST gaps and overlaps break schedules.Counting days: date differences, business days, and ISO weeksInclusive vs. exclusive counts, working days with holidays, month-end arithmetic, leap-day birthdays, and ISO week numbers.

Design & CSS

Colour contrast and WCAG: making text readableHow the contrast ratio works, the AA and AAA thresholds, real colour examples, and where contrast problems hide.Fluid typography with clamp() and type scalesBuild a modular type scale, make it fluid with CSS clamp(), and keep text zoomable for accessibility.

Files & archives

Checksums: verifying downloads with SHA-256What a hash proves, how to check a download on any system, and why a matching checksum is not the same as authenticity.ZIP and GZIP: how compression works and when it helpsWhat compresses and what does not, the difference between archives and compressed files, and how to handle untrusted archives.

Geography

Coordinates, great-circle distance, and bearingsLatitude and longitude notation, why the shortest route curves on a map, midpoints, and the coordinate-order trap.

Networking

CIDR and subnetting explainedRead prefixes and masks, plan subnets, understand private ranges, and see why some address ranges need several CIDR blocks.

Web & SEO

UTM parameters and campaign tracking done rightThe five UTM parameters, naming conventions that keep reports clean, and where UTM links must never be used.robots.txt, sitemaps, and meta tags: what search engines readWhat each file and tag controls, why blocking in robots.txt does not remove pages from results, and a launch checklist.

Prefer to get straight to work? All tools are listed on the home page.