Paragraph indent
The first line starts a little farther in, marking a new paragraph without adding a blank vertical gap.
See it
What it is
A paragraph indent offsets the first line horizontally to signal a new paragraph without adding a vertical gap. It is the compact convention seen throughout novels and other continuous prose. CSS provides it directly with text-indent.
Use an indent when the reading experience is continuous and conserving vertical space matters. About 1 to 2em is a sensible starting range, then tune it to the column width and typeface. The first paragraph after a heading or scene break usually stays flush because the break is already obvious.
The gotcha is the typewriter habit. On a typewriter the only way in was the tab key or five spaces, and that reflex still fills web copy with stray characters. Spaces, tabs, and nonbreaking spaces are content, not layout tools; their width is inconsistent and they can be copied or wrapped in surprising ways. Use text-indent, and avoid pairing a strong indent with a full blank line between every paragraph unless the double signal is intentional.
Ask AI for it
Set long-form article copy with book-style paragraph indents using CSS text-indent: 1.5em. Apply the rule only to article p + p, keep every first paragraph after h2, h3, blockquote, and hr flush left, and set paragraph margin-block: 0 so indentation is the sole paragraph marker. Use logical selectors and live HTML text, not tabs or nonbreaking spaces. Show the layout at 40ch and 70ch measures and verify that text selection and copy preserve clean paragraph content.