Locale Lab

Unicode CLDR · World Bank · Intl

Lessons and planning tools for software localization.

The same plural, layout, and encoding mistakes ship over and over. 21 short lessons reproduce each one in your browser. An atlas of 250 markets and three estimators cover the planning side: where to ship next, and what it costs.

Start the courseOpen the Atlas
Straight toPlural rulesText expansionRight-to-left layoutUnicode and string lengthWhich market nextWhat it costsGlossary
lessons
21 lessons6 units
territories
250 territoriesCLDR territory data
languages
581 languageswith a 0.1% share or more
people online
5.8B people onlinethe market the atlas sizes
Course

Learn what breaks

21 lessons, each a live demo plus a three-question check. Start anywhere; the order is a suggestion.

Atlas

Decide where to ship

Language and market data for every territory CLDR covers. Pick the languages you already ship and see the reach you are missing.

Tools

Price and check the work

Estimate a translation round, lint a strings file before it goes out, and see how each locale formats what you send.

One date, one number, one price.

Six locales, formatted by the browser rather than by hand. Month and day swap order, the decimal separator changes, digits change shape, and the currency symbol moves. Hardcode any of it and the product is wrong in most of the world.

Try it with your own values
A sample date, number, and price formatted in six locales
Locale9 Mar 20261234567.89Same, as money
English (US) en-USMar 9, 20261,234,567.89$1,234,567.89
German de-DE09.03.20261.234.567,891.234.567,89 €
French (Canada) fr-CA9 mars 20261 234 567,891 234 567,89 $
Japanese ja-JP2026/03/091,234,567.89￥1,234,568
Hindi hi-IN9 मार्च 202612,34,567.89₹12,34,567.89
Arabic (Egypt) ar-EG٠٩‏/٠٣‏/٢٠٢٦١٬٢٣٤٬٥٦٧٫٨٩‏١٬٢٣٤٬٥٦٧٫٨٩ ج.م.‏

The course, unit by unit

Visual failures first, then the APIs that prevent them, then the pipeline that ships the strings. Every lesson stands on its own if you only need the one.

Full syllabus
  1. 01

    Getting oriented

    1 lesson

    What localization work is made of

    Orientation
  2. 02

    Three failures you can see

    3 lessons

    Layout swell, formatting, plural grammar

    Text expansionFormattersPlurals & gender
  3. 03

    The Intl toolbox

    5 lessons

    The APIs that already know the answer

    Lists & rangesSortingTime zonesCalendarsLocale fallback
  4. 04

    Scripts and layout

    4 lessons

    Writing systems meet CSS

    Line-breakingCJK fallbackBiDiRTL mirroring
  5. 05

    Strings, names, and input

    4 lessons

    Data that comes from people

    Unicode pitfallsEncodingInput parsingAddress & name
  6. 06

    Shipping translations

    4 lessons

    The pipeline, the QA step, the final exercise

    Translation pipelinePseudolocLQA scoringCapstone audit

Formatting samples are computed with Intl in your browser. Languages and population come from Unicode CLDR; internet use, income, and account ownership come from World Bank Open Data. Every atlas figure traces to its source.