Practical guides for using the tools
Files, folders and sharing
Verifying a download with SHA-256
What a checksum is, how to compare one with the value a publisher gives you, and which algorithms are still safe.
2 min read
ZIP files explained: compression, encryption and broken archives
How ZIP compression works, why some files barely shrink, how ZIP passwords and encryption differ, and what to do when an archive will not open.
9 min read
PDFs and documents
Images and graphics
Video
Spreadsheets and data
Developer tools
Cron expressions explained, with examples
How the five cron fields work, common schedules, the day-of-month and day-of-week trap, time zones, and why some cron jobs never run.
9 min read
Unix timestamps and time zones explained
What a Unix timestamp is, how to tell seconds from milliseconds, how offsets differ from time zones, and the daylight-saving bugs that catch everyone once.
8 min read
Web design and accessibility
Colour contrast and WCAG: what AA and AAA mean, with examples
How the WCAG contrast ratio is calculated, the AA and AAA thresholds, real colour pairs that pass and fail, and how to fix low contrast.
8 min read
Favicons in 2026: which sizes and files you actually need
The few favicon files a modern website needs, the HTML to reference them, designing an icon that works at 16 pixels, and what to drop.
8 min read
SEO and website diagnostics
How to write a robots.txt file (and what it cannot do)
How robots.txt rules are matched, ready-to-use examples, how to test a path, and why blocking a page from crawling does not keep it out of search results.
7 min read
Open Graph tags and social preview images: sizes and fixes
Which Open Graph and Twitter Card tags a page needs, the image size that works almost everywhere, and how to fix link previews that are wrong or missing.
8 min read
Structured data and JSON-LD basics for small websites
What schema.org structured data is, how JSON-LD works, which types a small site needs, complete examples, and errors that stop it working.
8 min read
Writing title tags and meta descriptions that fit in search results
How search results truncate titles and descriptions by pixel width, a simple formula for writing both, worked examples and common mistakes.
8 min read
Marketing, business and ecommerce
Money and budgeting
Networking, security and device checks
IPv4 subnetting step by step: CIDR, masks and usable hosts
How to work out network, broadcast and host ranges by hand, with worked /26, /27 and /20 examples and a method for splitting a network into subnets.
8 min read
SPF, DKIM and DMARC in plain English
What the three email authentication records do, how to read them, and the most common mistakes that cause mail to be rejected.
2 min read
Strong passwords and passphrases: what entropy means
How to judge password strength in bits of entropy, why length beats complexity, and when a passphrase is the better choice.
2 min read
Understanding DNS records: A, AAAA, CNAME, MX, TXT and NS
What each common DNS record type does, how to read a zone with real examples, how TTL and caching work, and the mistakes that break websites and email.
9 min read