Text justification / rivers
Justification lines up both paragraph edges; rivers are the distracting white paths that oversized word gaps can form through it.
See it
What it is
Justified text makes both edges of a paragraph flush by adjusting the space within each line. A river is an accidental vertical or diagonal channel of white that appears when enlarged word spaces on neighboring lines happen to connect. Newspapers can make justification feel orderly; bad spacing makes it look cracked apart.
Reach for justification in book pages, reports, and multi-column editorial layouts where the firm edges support a grid. It works best with a long enough measure, good hyphenation, and a typesetting engine that fits the whole paragraph at once rather than one line at a time. That is the difference between Donald Knuth and Michael Plass's total-fit algorithm in TeX, or InDesign's Adobe Paragraph Composer, and the greedy line-by-line breaking a browser does. On the web, set the correct 'lang' attribute so automatic hyphenation has a language dictionary.
Gotcha: 'text-align: justify' alone is not composed typography. Narrow columns and long unbreakable words force huge gaps, while repeatedly pressing the space bar only hard-codes the damage. Check the paragraph from a distance or blur it slightly; rivers appear as paths before individual bad spaces do.
Ask AI for it
Typeset this article with CSS 'text-align: justify', 'hyphens: auto', and the correct HTML 'lang' attribute for its actual language. Keep paragraphs between 55ch and 70ch, preserve normal word spaces in the source, and leave the final line unforced. Add a diagnostic view that blurs the text with 'filter: blur(2px)' so vertical or diagonal rivers are easy to spot. If a river appears, adjust the measure or wording before changing global word spacing.