Guides & Tutorials
In-depth original tutorials on PDF handling, image compression, password security and time zones, so you get more out of every tool. Free to read.
How to use these guides
Each guide solves one concrete problem: principle first, then steps, then the mistakes people actually make. Guides do not depend on a tool page, so they read fine on their own.
Fastest way in: come with the problem you have. To learn an area properly, read principle, operation, then trade-offs. The mistake list at the end of each guide comes from real feedback and is worth a read on its own.
Guides link to the matching tools, which all run locally in your browser with no sign-up. Content is revised as tools change, and bigger revisions carry a date.
Guides & Tutorials (14)
The Complete Guide to Working with PDFs Online
How to merge, split and convert images to PDF online — steps, common issues, and why local processing protects your files.
Read guideImage Formats Explained: JPG vs PNG vs WebP
Lossy vs lossless, quality sweet spots, transparency, and a decision table for picking the right image format.
Read guideWeb Color & Contrast: WCAG Primer
How contrast ratios work, what AA/AAA require, common failing color pairs, and a step-by-step checking workflow.
Read guideQR Codes: Uses, Tips & How to Create
How QR codes work, sizing rules, error-correction levels, print tips, and static vs dynamic codes.
Read guidePassword Security 101: Strong Passwords
What makes a password strong, how entropy works, management strategies, hashing basics, and common mistakes.
Read guideDeveloper’s Handbook: URL Encoding, Base64 & JWT
Percent-encoding rules, how Base64 works, JWT structure and claims, plus debugging tips for all three.
Read guideJSON for Beginners: Syntax & Mistakes
JSON syntax rules, nesting, a table of the ten most common parse errors, and JSON vs XML vs CSV.
Read guideWhy Browser-Only Tools Are Safer
Where online tools leak data, how in-browser processing works, which files never to upload, and how to verify it yourself.
Read guideWorking Across Time Zones: A Practical Guide
UTC offsets, daylight-saving pitfalls, Unix timestamps, and practical scheduling tips for distributed teams.
Read guideHealth Metrics 101: BMI, BMR & Calories
How BMI is calculated, its limits, basal metabolic rate, activity multipliers, and sensible calorie strategies.
Read guideText Productivity: Dedupe, Sort & Clean
Three ways to dedupe lines, sorting workflows, capitalization rules, word-count uses, and character-level diffing.
Read guideThe Complete Guide to Unit Conversion
Conversion tables for length, weight, temperature and data size, the kB vs KiB trap, and how to handle precision.
Read guideID Photo Sizes: Charts, Backgrounds, and Self-Shooting Tips
Size charts in millimeters and pixels for common ID photos, background color guidance, and a checklist for shooting your own photo so it passes review.
Read guideCron Expressions: Cheat Sheet and Common Pitfalls
Field semantics, 14 example expressions, and special character notes, plus the traps: day OR day-of-week, missing 31sts, time zones, DST shifts.
Read guidePick a path by goal
- Working with PDF
Merge, split, images to PDF. Read the format basics, then follow merge, split, convert in order.
- Image compression and formats
what JPG, PNG and WebP are each good at, and how the compressor balances quality and size.
- Password security
How to weigh length against character sets, why forced rotation is outdated advice, and how to build a scheme you can keep up.
- Developer data workflows
JSON validation, Base64 and regex testing work as a chain: identify the data shape, then validate, convert, test.