IBAN check digits catch every wrong digit and nearly every letter typo
An IBAN's check digits caught every wrong digit we typed into SWIFT's 89 example IBANs, and missed a few errors that swa...
Guides & How-tos · Worked examples · Real numbers
Developer Tools guides
Step-by-step how-tos, head-to-head comparisons and honest roundups — every guide worked through with current figures, then backed by a RECATOOLS calculator or AI-directory entry so you can act on it.
498 guides published
17 topic areas
Latest guide Oct 2026
Statistics
33
Health & Wellness
31
Cybersecurity
30
Business
19
Privacy & Data
17
Consumer Tech
14
ASEAN Tech
13
Personality
9
Cloud & Infra
8
Cyber Threat Intel
7
Sustainability
5
Advertisement
A Korean learner's dictionary needs only 1,465 of Hangul's syllables
Unicode encodes 11,172 Hangul syllables by one formula, and South Korea's 1987 character standard kept 2,350 of them. Ho...
The same Shift_JIS bytes read as 髙 or 騠, depending on the table
Browsers and Microsoft's CP932 table read Shift_JIS the same way, but other converters do not. We decoded all 7,724 two-...
Advertisement
Neither Chinese punctuation standard requires full-width marks
Mainland China's punctuation standard and Taiwan's handbook measure marks in character cells and never require full-widt...
Chinese typing speed in WPM, and why dividing by five gets it wrong
Hong Kong's civil service asks for 15 Chinese characters a minute, which looks tiny beside English speeds only because t...
The most common Chinese typos are homophones
Most Chinese typos are the right sound and the wrong character, picked from a pinyin keyboard's row of candidates. Some...
What CSS ease and ease-in-out actually do
The default CSS easing, ease, is 80% of the way there at half the time, and it does not start from rest. We evaluated th...
What a seal script converter can and cannot do
Seal script got its own Unicode block on 16 September 2026 — 11,328 characters — and a converter will still leave 的, th...
Why Hong Kong place names don't follow Jyutping
荃灣 is Tsuen Wan and 杏花邨 is Heng Fa Chuen, though 荃 and 邨 sound the same. We converted 2,870 official Hong Kong na...
How Zhuyin (bopomofo) maps to pinyin, and where a simple chart goes wrong
Zhuyin's 37 symbols line up with pinyin letters, so a chart gets you most of the way. But against every syllable in Taiw...
Converting one passage between mainland, Taiwan and Hong Kong punctuation
Taiwan centres its full stops and the mainland puts them bottom left, yet it is the same character. Here is one passage...
Why common Cantonese characters like 嘅 and 咗 could not be typed in Big5
Eleven of the most-used written Cantonese characters, including 嘅, 咗 and 喺, could not be typed in Big5, the tradition...
Why a Chinese character that works in GBK can break in Big5
GB2312, GBK and Big5 write the same Chinese character with different bytes, and none of them can write every character....
Stripping the dots from an email address can merge two different people
Only Gmail's consumer domain and Proton document dots as ignorable. On Google Workspace dots change the address, so two...
The payment QR on the counter is a line of text you can read
ASEAN merchant payment codes all use one published format: a flat string of tag, length and value. Decoding a real paylo...
No ASEAN country has opened the whole 6 GHz band, and China opened none of it
Six ASEAN countries released the bottom 500 MHz of the 6 GHz band and stopped; the United States released all 1,200. Onl...
127.0.0.1 is one of sixteen million loopback addresses
IPv4 reserved the whole of 127.0.0.0/8 for loopback, and the RFC that did it never names 127.0.0.1. Whether the other 16...
WCAG asks for 24 pixels, not the 44 everyone quotes
The 44-pixel tap target is quoted everywhere as the accessibility requirement. It is WCAG's Level AAA figure. The criter...
Z and +00:00 stopped being the same thing in 2024
RFC 9557 moved Z across to mean the instant is known and the local offset is not, while +00:00 kept its older meaning. T...
Valid JSON is not one thing, and three runtimes prove it
A fourteen-byte document containing a lone surrogate escape parses in Node, parses in Python and is refused by PHP — all...
Four ASEAN countries have no time zone of their own
Asia/Phnom_Penh, Asia/Vientiane, Asia/Kuala_Lumpur and Asia/Brunei are not time zones. They are links, and the files beh...
One cron line, three different answers
Ask three tools how often 0 0 */2 * 1 runs in September 2026 and you get two firings, seventeen, or four. Cron switches...
MCP deleted the handshake every tutorial teaches
The Model Context Protocol revision of 28 July 2026 removed the initialize handshake, the session header and the server'...
How to Self-Host Home Assistant with Docker
Running the container instead of a supervised install gives up the add-on store, which is a real trade. And bridge netwo...
Advertisement