Font Tester
Test a font for the things that actually matter: measure width, ambiguous glyph pairs, accent coverage and character set size.
Convert with this tool
or choose a file from your device — it is processed in this tab and never uploaded
Accepted: TTF, OTF, WOFF, WOFF2
Files stay on your device. There is no upload, no queue and no watermark, so a conversion works even with the network switched off after the page has loaded.
Supported formats & processing
| Accepted input | TTF, OTF, WOFF, WOFF2 |
|---|---|
| Produced output | A legibility and coverage report — no file is produced |
| Processing | Web Audio API + canvas + native JavaScript encoders |
| Upload required | No — the file is read locally and never transmitted |
How to use this tool
- Add the font fileIt is registered and every sample below re-renders in it.
- Read the ambiguity samplesLook at the rn/m pair and the I, l and 1 row first.
- Set the measure width45–75 characters per line is the comfortable range for body text.
- Check the accent rowAny character that falls back to another font will look subtly different.
- Read the coverage figuresThe result card reports the real mapped code point count.
About this tool
A font can look beautiful in a specimen and fail badly in use. The classic failure is the letter pair rn rendering as an m, or I, l and 1 becoming indistinguishable in a data table. Another is a font that covers Latin but silently falls back to a system font for accented characters.
This tester sets the specific strings that reveal those problems and reads the font's real cmap table to report how many characters it actually maps. The measure control sets a line to exactly the character count you choose, which is the correct way to judge whether body text will be comfortable to read.
Features
- Ambiguity samples for the classic problem letter pairs
- Measure control that sets a line to an exact character count
- Numeral, symbol and accent coverage rows
- Real cmap parsing for an accurate mapped code point count
- Warning when character coverage is too low for general text
- All samples render in your actual font file
Frequently asked questions
What is the ideal measure?
Between 45 and 75 characters per line for body text. Below 45 the eye jumps too often; above 75 it loses its place returning to the next line. The measure control lets you set a line to exactly that width and see it in your font.
Why do the accented characters look different?
The font does not contain them, so the browser falls back to another family for those code points. The coverage figure in the result card tells you how many characters the font actually maps.
What does the rn/m test show?
Whether the font distinguishes the two-letter pair rn from the single letter m. In poorly designed fonts they are nearly identical, which causes misreading in small text.
Does the tester work with variable fonts?
Yes. Variable fonts respond to the weight control across their full axis, so you can test how legibility changes from Light to Black.