Missing Glyph Detector
Face & characters
Detection uses document.fonts.check(), the browser's own font-matching API — the same machinery that decides at paint time whether to substitute a fallback.
Honest rendering
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Coverage by block
| Block | Covered | Share | Note |
|---|---|---|---|
| No matches for “”. | |||
Character detail
| Char | Code point | Rendered by | Block |
|---|---|---|---|
| No matches for “”. | |||
Search the table to check a specific character or block.
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The missing glyph detector asks the browser's own font-matching engine whether a face can render each character in your text. That is the real answer rather than a heuristic: the same check that decides at paint time whether to substitute a fallback.
What is Missing Glyph Detector?
The missing glyph detector takes a face and a string of text, then reports which characters the face can draw and which will be substituted by a fallback. The test is the browser's font-matching check — document.fonts.check — which is the machinery that already decides this at paint time, so the result describes what a visitor will see rather than what a specification claims.
Coverage is summarised by block-like groups, which is how a font's repertoire is usually described.
- Basic Latin, the ASCII range, followed by the Latin-1 supplement that carries Western European accents and the common legal marks.
- General punctuation and currency, which are the two ranges where an incomplete face tends to fail quietly.
- Arrows and mathematical operators, then the symbols and dingbats range, which few text faces cover fully.
- CJK and the emoji range, the two groups where a face either commits to a large repertoire or has nothing at all.
The readouts add up the picture: the unique character count, how many are covered, how many need a fallback, and the coverage as a percentage of the sample. The per-group table then shows coverage as a fraction and a share, with a note naming the missing count wherever a group is incomplete, which is the line that matters when a page is expected to render currency symbols or arrows reliably. A detail table lists every character with its code point, whether the face or a fallback draws it, and its group, and it can be searched, so a single character can be confirmed without reading the whole list.
The honest rendering panel is the part that makes the result tangible. The text is drawn at a large size in the chosen face, and the characters that will be substituted are named by code point below it, so the difference between coverage and rendering is visible: a character can be present in the face and still look wrong at a particular weight, and a character reported as covered is not a claim about how well it is drawn.
Four limits follow from asking the browser rather than reading the file.
- Detection depends on the font being loaded and available, so a webfont that has not arrived reports as unavailable along with everything else.
- The result is specific to the platform's fonts, which means a machine with a different fallback set can produce a different report for the same file.
- The group list is eight practical buckets rather than the full Unicode block taxonomy, so a character outside them is labelled as other and left out of the summary counts while still appearing in the detail table.
- The check answers the availability question only, so a glyph that is present but drawn at a weight too light for its size passes without comment.
Run it after the fonts have loaded, on the platform whose fallbacks matter most, and the report names exactly which characters will be substituted before the page ships.
How to use Missing Glyph Detector
- Choose the face under test, then paste the real text the page will render rather than a shortened sample.
- Read the coverage percentage and the missing count first, since those two numbers summarise the whole result.
- Check the per-group table for the ranges the project depends on, noting any group that is only partly covered.
- Search the detail table for the specific characters that matter, and treat the honest rendering panel as the final check.
When to use Missing Glyph Detector vs related tools
Reach for it when a page renders a symbol, a currency mark or CJK text and the fallback behaviour has to be known before launch, when a webfont is being chosen and its coverage is being asserted rather than tested, or when a character on the page has rendered in a visibly different face. Coverage rather than aesthetics is the question. For identifying an unknown character the Unicode character explorer is the first step, the Unicode block explorer explains the planes and byte costs, and the glyph browser measures the glyphs the face does carry.
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.