Why compare at the same size when faces differ in apparent size?

Because the first pass should be fair. Once the faces are side by side, adjusting the size so the x-heights match is what shows the real difference in proportions. Comparing a face at its ideal size against another at a poor one is how a good candidate gets eliminated for the wrong reason.

What does the ambiguous string test?

It tests legibility under the conditions that actually cause misreadings: a capital O against a zero, a lower-case l against a digit one, S against five, and so on. A face that survives that string at a small size is much less likely to produce a confusing identifier, password or model number.

How do I tell lining figures from old-style ones?

By height and alignment. Lining figures are all the same height and sit on the baseline, so they align with capitals; old-style figures have ascenders and descenders and sit within the text flow, which reads more comfortably in prose but breaks the alignment of a column of numbers.

Does the tool measure the faces it shows?

No, it renders them. Everything in the guidance table is judged by eye, and the numbers that a design decision may depend on — advance widths, coverage, pair adjustments — come from the measuring tools. That division is deliberate: measurements without a rendering are hard to interpret, and renderings without measurements hide the facts.

Why is there no overlay mode?

Because the useful comparisons here are between characters as they read, not between outlines. Overlaying two faces shows structural differences, which matters when designing a companion, while reading the same string in two faces shows the difference a page will actually present.

Glyph Comparison Tool

Characters & settings

Characters (newlines allowed)

Sizepx

Weight

Layout

Stacked rowsColumns

Families (6 selected)

Comparison

Inter · sans

ABCDEFGHIJKLMNOPQRSTUVWXYZ
abcdefghijklmnopqrstuvwxyz

Fraunces · serif

ABCDEFGHIJKLMNOPQRSTUVWXYZ
abcdefghijklmnopqrstuvwxyz

Playfair Display · serif

ABCDEFGHIJKLMNOPQRSTUVWXYZ
abcdefghijklmnopqrstuvwxyz

Lora · serif

ABCDEFGHIJKLMNOPQRSTUVWXYZ
abcdefghijklmnopqrstuvwxyz

Source Serif 4 · serif

ABCDEFGHIJKLMNOPQRSTUVWXYZ
abcdefghijklmnopqrstuvwxyz

Merriweather · serif

ABCDEFGHIJKLMNOPQRSTUVWXYZ
abcdefghijklmnopqrstuvwxyz

What to look for

Feature	Why it decides the pairing
x-height	Two faces with different x-heights look different at the same nominal size; set sizes by x-height, not by number.
Single vs double-storey g/a	Changes the texture of body text and how neutral the face reads.
Numeral style	Old-style figures sit in the text flow; lining figures align with capitals — tables usually need tabular lining.
Terminal cuts	Horizontal terminals read technical; angled terminals read humanist.
Contrast axis	High-contrast faces need larger sizes than low-contrast ones before they become hard to read.

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The glyph comparison tool renders the same characters in several families at once, so a pairing decision is made on evidence rather than on specimens seen separately. Five comparison presets cover the characters that usually decide the question.

What is Glyph Comparison Tool?

The glyph comparison tool sets one string of characters in as many faces as you select, at a common size and weight, so the differences are visible side by side rather than remembered from separate previews.

The five comparison presets are chosen for what they expose.

Alphabet, which shows proportions and the general texture of a face in two lines.
Numerals, which reveals whether the figures are lining or old-style and whether the family carries more than one figure set.
Ambiguous, a string of easily confused character pairs — capital O and zero, capital I, lower-case l and the digit one, S and five, Z and two, B and eight, G and six, plus r followed by n — which is where a face's legibility under strain is decided.
Punctuation, which shows the quotes, dashes, ellipsis and symbols a face draws and how it draws them.
Lower-case shapes, a short set of the letters whose forms vary most between grotesque, humanist and geometric traditions.

The settings are deliberately narrow so the comparison is fair. Size runs from 12 to 160 pixels and weight from 300 to 700, and both apply to every selected family at once, which means the comparison is like for like rather than each face at its own best setting. The layout switches between stacked rows and two-column groups, and the family chips add or remove faces from the set, so the same characters can be compared across a longlist and then a shortlist.

The table beside the comparison is the reading guide, and it names the five things worth looking at. The x-height decides how large a face appears at a given nominal size, so two candidates with different x-heights should be compared by adjusting the size until they look equal rather than by trusting the number. The single or double-storey form of g and a changes the texture of body copy and how neutral the face reads. The numeral style decides whether figures sit inside the text flow or align with capitals, with tabular lining figures the requirement wherever numbers are compared in columns. Terminal cuts carry the voice: horizontal terminals read technical and angled ones humanist. And the contrast axis decides the size at which a face stops being comfortable, since a high-contrast design needs a larger setting than a low-contrast one.

What the tool does not do is measure, and three further limits follow from comparing by rendering.

Every entry in the guidance table is a judgement made by eye, so a decision about widths, coverage or metrics belongs with the measuring tools.
The catalogue is the source of faces, so a licensed family has to be judged from its own specimen rather than here.
Weight is uniform across families, which means a face without the requested weight is drawn with a synthesised version that will not match its real forms.
There is no overlay or superposition mode, so old-style figures, x-heights and terminal cuts are compared across rows rather than stacked on top of one another.

That last limitation is deliberate: reading the same string in two faces shows the difference a page will present, while stacking outlines shows a difference only a designer would see.

How to use Glyph Comparison Tool

Pick the preset that matches the question, since the ambiguous string and the numerals string answer different concerns.
Select the faces to compare and keep the longlist long enough to see the range before narrowing it.
Set a size and weight that apply to every face, then adjust the size so faces with different x-heights appear equal before judging anything else.
Read the comparison against the guidance table, then take the two finalists into a measuring or pairing tool for the decisions a preview cannot settle.

When to use Glyph Comparison Tool vs related tools

Reach for it when a shortlist of faces has to be narrowed on the characters that actually differ, when a face that looked right in a specimen fails in a layout and the reason has to be found, or when two families are being considered for one page and their numerals or lower-case forms need to be seen together. The preset strings are the useful part. For a whole page of faces at once the multi-font comparison sets running text in parallel, the font pairing suggester proposes combinations, and the glyph browser reports the advance widths the comparison cannot measure.

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.