Line-Height Is the Cheapest Readability Upgrade for Your Notes

Your browser hands your notes a line-height of roughly 1.2 by default, and 1.2 is cramped. The accessibility floor for comfortable reading is 1.5; the typographer's craft range is 120 to 145 percent of the font size. There is no single perfect number — it scales with your line width and typeface.

The number hiding in that default is line-height: the vertical distance from one line of text to the next ¹. Leave it unset and the browser supplies its own. The CSS specification recommends a used value between 1.0 and 1.2 for the automatic normal ², and in practice desktop browsers settle near 1.2 ³. Typeset a long note at 1.2 and the lines press together.

Three authorities set the comfortable range higher, and they do not agree, which is the interesting part. The accessibility guidelines put the floor at 1.5 ⁴. Matthew Butterick puts the craft range at 120 to 145 percent ¹. The gap between a low-vision floor and an aesthetic ceiling is exactly why your editor's default is a design decision, not a neutral fact.

What line-height should your notes use?

For on-screen notes, set your line-height between 1.4 and 1.5. That range sits at the top of the typographer's craft band — Butterick recommends 120 to 145 percent of the font size — and meets the accessibility floor of 1.5. Below roughly 1.3 the lines crowd; past 1.6 they read as loose, disconnected strips rather than a block.

Start at 1.5 and adjust down if it looks airy. A unitless value like line-height: 1.5, rather than a fixed pixel height, is the durable choice, because it scales when you change font size and never traps a line at a height that no longer fits ¹. Set it once at the document level and every paragraph inherits it.

One number, applied everywhere. That is the whole upgrade.

Why do your notes default to a cramped 1.2?

Because you never chose the number. When a stylesheet leaves line-height at its initial value, normal, the browser fills it in. The CSS specification recommends a value between 1.0 and 1.2 for normal, and desktop browsers, per MDN, land on roughly 1.2, depending on the font. Your cramped notes inherited a default, not a decision.

normal is not a fixed constant. The CSS specification is explicit that it recommends a used value between 1.0 and 1.2, and leaves the exact figure to the browser ². MDN records where they land: roughly 1.2, depending on the element's font-family ³. That is fine for a single heading and punishing for a screenful of prose.

Changing it changes only how the note looks — the Markdown on your device reads the same, byte for byte. Nobody chose 1.2 for your notes. The browser did.

The accessibility floor: space-and-a-half

The Web Content Accessibility Guidelines set the readability bar at 1.5. Success Criterion 1.4.8, Visual Presentation (Level AAA), requires that line spacing is at least space-and-a-half within paragraphs. That is 1.5 — a floor built for low-vision readers, above the browser default and above the typographer's ceiling. Generous, not wrong.

SC 1.4.8 is Level AAA, the highest bar, and it is written for the readers who need the extra air most ⁴. Meeting 1.5 is not a legal obligation for a personal note file. It is a well-tested lower bound: if the strictest readability criterion asks for space-and-a-half, your own long notes are unlikely to want less.

The strictest guideline sets the floor at 1.5. Start there.

The portability check: survive a 1.5x override

There is a second, sneakier requirement. Success Criterion 1.4.12, Text Spacing (Level AA), says a reader must be able to override your text's line height (line spacing) to at least 1.5 times the font size with no loss of content. It is not about your default; it is about whether your notes break when someone loosens them.

The criterion lists four overrides a reader may impose without breaking your text: line height to at least 1.5 times the font size, spacing following paragraphs to at least 2 times, letter spacing to at least 0.12 times, and word spacing to at least 0.16 times ⁵. Text that collapses under those values was too tightly built to begin with. Notes in plain Markdown pass this by default, because there is no fixed layout to shatter.

Good text survives being loosened. Fragile text does not.

The craft range: 120 to 145 percent

Typographer Matthew Butterick puts working line spacing at 120 to 145 percent of the point size. In a word processor's Lines field that is 1.03 to 1.29; in CSS, a unitless line-height of 1.2 to 1.45. The point is a habit, not a constant: stop defaulting to single or double spacing and set the space between lines on purpose.

Butterick is blunt about where the cramped habit comes from. "Most writers use either double-spaced lines or single-spaced lines—nothing in between—because those are the options presented by word processors," he writes. "These habits are obsolete typewriter habits" ¹. The 120-to-145 range is his replacement: a deliberate middle the typewriter never offered.

Single or double was a machine's limitation, not a reading choice.

Why there is no single perfect number

Leading is not set in isolation. Robert Bringhurst's rule, adapted for the web by Richard Rutter, is to choose a basic leading that suits the typeface, text and measure. Wider columns need more leading so the eye finds the next line; a tall x-height needs a touch more air. The right number is relational, not absolute.

Bringhurst, in Rutter's adaptation, frames leading as a rhythm you tune to the whole setting: "Vertical space is metered in a different way [to horizontal space]... This unit is the leading, which is the distance from one baseline to the next" ⁶. The controlling variable is measure, the line width, and a note has no fixed width, so the right leading shifts as your window does. Typeface matters too: a large x-height fills the line and wants more space above it, which is one more reason the font you read in changes the number.

Ask not for the best number. Ask what suits this typeface at this width.

What the research shows, and what it does not

Here is the honest limit. The one controlled study behind this, Ling and van Schaik (2007), measured visual search — finding a target on a page — not reading speed. Wider line spacing led to better accuracy and faster reaction times. It says nothing about how fast you read prose. Line-height helps comfort and scanning; do not sell it as speed.

The study's own summary is careful. Ling and van Schaik set out to "generate design guidelines for the production of web pages," and report that "varying text presentation had a significant effect on task performance, with wider line spacing leading to better accuracy and to faster reaction times" ⁷. Every one of those measures is a search task. The literature on line spacing and continuous-prose reading speed is thin and mixed. Claim comfort and scanning. Do not claim you will read faster.

The evidence is about finding, not reading. Respect the difference.

How to fix it in your own notes

You need one setting, not a new tool. Find the line-height (or line spacing) control in whatever you write in, and move it to 1.5. If your editor exposes only a preset, pick the loosest comfortable option. Read a full screen of your own notes at the new value before you decide. The change costs a single number.

The mechanics are trivial. In CSS, line-height: 1.5. In a word processor, set Line spacing to Multiple and type 1.5, or use Butterick's 1.03-to-1.29 Lines values if you want the tighter craft band ¹. This is the cheapest readability upgrade your notes have: no new app, no new file format, one number.

Change the number. Read a screen. Keep what feels calm.

Frequently Asked Questions

The short version: your notes probably render near 1.2 because you never set line-height, the accessibility floor is 1.5, and the typographer's craft range is 120 to 145 percent of the font size. These answers cover the numbers most people search for, and where they come from.

What is the best line spacing for reading?

For reading on screen, 1.5 is a safe, generous choice: it meets the accessibility floor in WCAG SC 1.4.8 and sits just above the typographer's craft range of 120 to 145 percent. There is no universal best — the ideal rises with wider lines and larger x-heights, so tune it to your own column.

What line-height should I use for body text?

Aim for a unitless line-height of 1.4 to 1.5 for on-screen body text. That covers Butterick's craft band of 120 to 145 percent of the font size and reaches the 1.5 accessibility floor. Use a unitless number rather than a fixed pixel value so the spacing scales with the font size.

What is the default line-height in CSS?

The CSS default is the keyword normal, which the browser resolves for you. The CSS specification recommends a used value between 1.0 and 1.2, and MDN notes that desktop browsers land on roughly 1.2, depending on the font. So most unstyled text renders at about 1.2 — tight for long reading.

Does line spacing affect readability?

Yes, for comfort and scanning. In a controlled study, Ling and van Schaik found wider line spacing improved accuracy and reaction time in visual search. Accessibility guidelines treat 1.5 as a readability threshold. Note the honest limit: that research measured finding things on a page, not how fast you read continuous prose.

Is 1.5 line spacing good?

For screen reading, yes. 1.5 satisfies WCAG SC 1.4.8, the AAA readability criterion, so it is a defensible, accessible choice. It sits a little above Butterick's 145 percent craft ceiling, which makes it generous rather than wrong. If 1.5 looks slightly loose with your typeface, 1.4 is still comfortable.

Why does my text look cramped or too tight?

Most likely you inherited the browser default. With no line-height set, text renders at normal, about 1.2 per MDN, which presses lines together and makes a long note feel crowded. The fix is one setting: raise line-height toward 1.5 and the same words gain room to breathe.

What's the best line spacing for reading long notes?

More than the roughly 1.2 you inherited by default. Set line-height to somewhere in 1.4 to 1.5, above Butterick's craft floor of 120 percent and at the accessibility mark of 1.5, then scale it to your line width: the wider your column, the more leading long notes want.

Your editor's line-height is not a fact about your notes. It is a choice, usually made by a browser that guessed 1.2. Reading gets easier the moment you take the choice back.

MNMNOTE keeps your notes in open Markdown on your own device, and how they render — line-height included — is yours to see and set: mnmnote.com.