Why must an index never be hyphenated?

Because a hyphenated term becomes two fragments that a reader cannot find. Someone searching the index for letterspacing will not look at a line ending in letter with spacing on the next line. The generated CSS therefore disables hyphenation outright, which is the one place in a typeset book where ragged word spacing is preferable to a break.

What does the runover indent do?

It aligns the second and later lines of a long entry with the first line's text rather than with its start, so the entry reads as one unit. It is built from a left padding and an equal negative text indent, which is the same technique a hanging indent uses. Without it, a wrapped page list looks like a separate entry.

Why are page numbers set in tabular figures?

So that the numbers form a column the eye can scan. Proportional digits have different widths, so the ones and twos would not line up vertically and the reader would have to read each number instead of scanning. Tabular figures make every digit the same width, which is what a page-number column depends on.

How many columns should an index have?

Two or three for a printed book, with two the usual choice. A single-column index is only justified on a very narrow page, because an index is read by scanning short entries and a wide single column wastes the scan. The tool reports entries per column and the resulting column height, which is what tells you whether the count fits the pages you have.

Does the tool sort the entries?

No. Entries are set exactly as typed, so sorting, merging duplicate terms and normalising page ranges all happen before the text is pasted in. The one thing it reads from the input is the sub-entry marker, which is a leading dash on the term.

Index Page Layout Preview

Index settings

Heading

Columns

Entry sizept

Leadingpt

Runover indentem

Sub-entry indentem

Hanging indentem

Entries (term, pages — prefix sub-entries with “—”)

Entries9

Entries per column5

Sub-entries2

Column height69pt

Typeset index

Index

alphabet14, 42, 88
alignmentoptical, 61–63, 74
baseline grid29, 30, 52
harmony55
rhythm52, 58
colourof type, 96–101
kerning47, 112
letterspacing44, 58
measure27, 68, 71

2 column(s) · 9.5pt on 11.5pt

Index conventions

· Page numbers are set with tabular figures and are never tracked; the reader scans the column, not the line.
· The runover indent marks continuation lines, so a long entry is visually one entry rather than two.
· Sub-entries sit under their parent with a smaller indent than the parent's own start — hierarchy by position, not by size.
· Two or three columns are the norm for print; a single-column index is only justified on very narrow pages.
· Hyphenation is disabled: hyphenating a term would make it unfindable.

Index CSS

.index {
  font-size: 9.5pt;
  line-height: 11.5pt;
  column-count: 2;
  column-gap: 6mm;
  hyphens: none;
}

.index li {
  padding-left: 2em;   /* runover indent for continuation lines */
  text-indent: -2em;
  margin-bottom: 1.72pt;
}

.index li.sub { padding-left: 3.1em; }

.index .pages { font-variant-numeric: tabular-nums; }
.index .head { padding-right: 0.5em; }

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The index page layout preview sets a book index as it is actually read: a two-column page with runover indents for continuation lines, sub-entries under their parents, and a page number column that aligns by digit. The indents and the column count are the two decisions that decide whether an index can be scanned.

What is Index Page Layout Preview?

The index page layout preview takes one entry per line as a term and its page numbers, then sets the column count, the entry size and leading, and three indent values, returning a typeset index, a column breakdown and the CSS.

Entries are typed one per line as a term followed by commas and page numbers, and a line whose term begins with a dash is treated as a sub-entry.
The column count runs from one to three, with two as the default, since two or three columns are the norm for a printed index.
Entry size runs from 6pt to 14pt and leading from 8pt to 20pt, defaulting to 9.5pt on 11.5pt.
A hanging indent puts continuation lines under the term rather than under the entry number, using a left padding and an equal negative text indent.
The readout reports the entry count, the entries per column, the number of sub-entries and the resulting column height in points.

The runover indent is what makes a long entry read as one entry rather than two: a term whose page list wraps onto a second line starts that line aligned with the term, so the reader's eye does not have to decide whether a new entry has begun. Sub-entries take a further indent, which places them under their parent by position rather than by size, and the convention list in the panel states the reason: hierarchy in an index is expressed by where a line starts, not by making it smaller. Page numbers are set with tabular figures so the digits align down the column, and hyphenation is switched off entirely, because a hyphenated term is a term a reader cannot find. The column height figure is the leading multiplied by the entries per column plus one line, which is the estimate a page plan needs to know whether the index will fit its allotted pages.

Entries are set exactly as typed. Nothing sorts them, merges duplicates or normalises a page range.
The hanging indent slider is present but not wired into the generated CSS; the runover indent is what sets the hanging value in practice.
Sub-entries exist at one level only, and a further level has to be added by editing the CSS.
Column balancing is left to the browser, so the last column can be short by several lines.
Cross-references, see-also entries and any styling that distinguishes them are outside the tool.

Use it when an index is being set and the indent scheme is still being decided, when a generated index has to be restyled to fit a page, or when a column count needs checking against the number of entries before pages are allocated. The entry and column counts are what a page plan is built from. Where the page geometry has to be fixed first, the book interior layout preview reports the text block the index will occupy, and the table of contents typesetter covers the contents page that mirrors it at the front of the book.

How to use Index Page Layout Preview

Paste the entries one per line, with the term first and its page numbers after commas, prefixing sub-entries with a dash.
Set the column count, the entry size and the leading, then choose the runover and sub-entry indents.
Read the entry count, entries per column and column height to see whether the index fits the pages it has been allotted.
Copy the index CSS, which carries the runover indent, the disabled hyphenation and the tabular figures for the page numbers.

When to use Index Page Layout Preview vs related tools

Reach for it when an index is being typeset for print, when a generated index from a word processor needs to be made scannable, or when the space an index needs has to be estimated before pages are allocated. It is also the quickest way to show why hyphenation must be off in an index. For the page it sits on, the book interior layout preview gives the text block and margins, the table of contents typesetter covers the contents page, and the print type specification sheet records the index size in points for the printer.

Privacy & Security

This tool runs entirely in your browser — no data ever leaves your device. There is no server round-trip, no upload, no logging, and no account required. Your input is processed locally using client-side JavaScript and is never stored, transmitted, or accessible to anyone else. When you close the tab, everything disappears.