Matterhorn 31-012 · PDF/UA-1 UA1:7.21.4.2-1

Type 1 CharSet that leaves out glyphs the font has

BlockerCheckpoint 31: FontsWCAG 1.3.1 (A)

CharSet must accurately list the glyphs in the embedded subset.

The condition, as the protocol states it. “The FontDescriptor dictionary of an embedded Type 1 font contains a CharSet string, but at least one of the glyphs present in the font program is not listed in the CharSet string.”

Matterhorn Protocol 1.1, checkpoint 31, index 31-012, section UA1:7.21.4.2-1. Software can decide this one on its own.

Processors may mis-handle the subset.

What CharSet is

/CharSet is an optional entry in the font descriptor of a Type 1 font: a string of glyph names, each written as a PDF name, listing what the embedded subset contains. .notdef is left out, because every font has it.

PDF/UA-1 does not require the entry, but if it is there it has to be true. It must name every glyph present in the font program, whether the document uses that glyph or not. This condition is a CharSet that leaves one out; the opposite failure, a CharSet naming a glyph the program does not have, is 31-013.

The file Taggart’s test suite uses for this page has a Type 1 font embedded as CFF, with four glyphs:

<< /Type /FontDescriptor
   /FontName /JBATCH+CharSetShort
   /Flags 32
   /FontFile3 9 0 R          % /Subtype /Type1C — glyphs .notdef, A, B, C
   /CharSet (/A/B)           % C is in the program and not in the list
>>

The page shows AB. C is never drawn, and that is beside the point: it is in the program, so it belongs in the list.

Why the entry exists, and who reads it

CharSet lets a processor know what a subset can draw without opening the font program. PDF/A-1 made it mandatory for Type 1 subsets, which is why so many files carry one. PDF/UA-1 only asks that, where it exists, it agrees with the program — a description that may be wrong is worse than none, because the software reading it has no way to tell.

Nothing different. Drawing goes to the font program and reading goes to the encoding or the ToUnicode CMap; neither looks at CharSet. The test file renders and copies as AB with the entry wrong, and would with it right.

That is worth saying plainly, because the condition is reported as a blocker and it is easy to assume a blocker means a reader is losing something. Here the reader is not. The file is non-conformant because it misdescribes its own font, and the cost of that falls on software that believes the description.

Where it comes from

Glyphs that come along with other glyphs. A Type 1 font can draw an accented letter by combining a base letter with an accent, so a subset containing é may also have to contain e and acute. A producer that writes CharSet from the characters it set, rather than from the program it actually embedded, leaves the components out.

A program replaced without its descriptor. A tool that re-subsets or swaps the embedded font program and copies the old descriptor across can leave a CharSet describing a different subset, missing glyphs in one direction or the other.

Hand-edited font dictionaries, where the list and the program were never compared at all.

How to check it free

veraPDF tests it under clause 7.21.4.2. Its rule applies only to fonts whose name carries a subset tag — six capital letters and a plus sign, as in ABCDEF+Garamond — so a full font with an inaccurate CharSet passes veraPDF on this point.

Acrobat Pro can show both halves. Following Adobe’s guide to advanced preflight inspections, select Use print production → Preflight from the All tools menu, then Options → Browse Internal PDF Structure, and find the font descriptor: its CharSet string is there. Then, from the same Options menu, Create Inventory — Adobe says the inventory shows the glyphs in each font. A glyph in the inventory that is not in the string is this condition.

How to fix it free

Delete the entry. It is optional, and the requirement only applies when it is present, so removing it resolves the condition without touching anything that draws or reads text. Acrobat cannot do this — Adobe’s structure browser lets you look at font objects but not edit them — but a short script with the free Python library pikepdf can:

import pikepdf

with pikepdf.open("in.pdf") as pdf:
    for obj in pdf.objects:
        if isinstance(obj, pikepdf.Dictionary) and obj.get("/Type") == "/FontDescriptor":
            if "/CharSet" in obj:
                del obj["/CharSet"]
    pdf.save("out.pdf")

Unless the file also claims PDF/A-1. PDF/A-1 requires CharSet on every Type 1 subset, so deleting it trades one failure for another. Check the document’s XMP metadata for a pdfaid:part of 1; if it is there, rebuild the string from the glyph names in the program instead, or re-export.

Re-export from the source, if the producer is one that writes CharSet correctly. If the same producer wrote this one, it will write the same thing again.

What Taggart does

Taggart does not detect this condition, because it does not open embedded font programs. On the test file — an embedded Type 1 font whose CharSet leaves out a glyph — it reports nothing about the font. The condition is instead on Taggart’s list of those it does not check, and no PDF/UA claim is made or written into the file until a person confirms that list.

What it reports under 31-012 is a narrower case it can decide from the dictionaries alone: a font descriptor with a CharSet and no embedded program for it to describe.

/JBATCH+CharSetShort declares a /CharSet string but has no embedded font program to describe.

That font is reported under 31-009 as well, and 31-009 is the one to act on: once the font is embedded, the CharSet has something to be compared with. Taggart applies that narrower check to any font with a CharSet, with or without a subset tag. For the condition this page is about, use veraPDF or the inventory comparison above before you confirm it.

How Taggart handles it

Software could decide this one, and Taggart does not check it yet. A clean report from Taggart says nothing about it either way. It is on the list of conditions Taggart asks you to confirm before it writes the PDF/UA claim into the file; check it by hand or with another validator, as described above.

Whatever Taggart changes, the page still looks identical. Fixes edit the PDF object model, not the content streams, and every remediation is re-rendered and compared against the original at structural similarity ≥ 0.999 before you get the file back. A tool that quietly reflows your document is worse than no tool.

Frequently asked questions

Does an incomplete CharSet change what a screen reader reads?

No. Neither drawing nor extracting text consults CharSet: the viewer reads glyphs from the font program and characters from the encoding or ToUnicode CMap. The condition is about the file describing itself accurately, and its cost falls on software that trusts the description.

Is it safe to delete the CharSet entry?

For PDF/UA, yes: the entry is optional, and the requirement only applies when it is present. PDF 2.0 deprecates it. The exception is a file that also claims PDF/A-1, which requires CharSet on every Type 1 subset; there, rebuild the list rather than removing it.

Why would a subset contain glyphs no text uses?

Because some glyphs are built from others. A Type 1 accented letter can be drawn by combining a base letter and an accent, and those two have to travel with it, so the subsetter keeps them. A producer that writes CharSet from the characters on the page, rather than from the program it embedded, leaves them out.

Does this apply to TrueType or CID fonts?

No. CharSet is meaningful only for Type 1 fonts, including Type 1 fonts embedded in compact form as CFF. A CID font describes its subset with a CIDSet bitmap instead, and the same rule in that form is condition 31-014.

Where this sits in the standards

Standards this condition maps to
Standard	Reference
Matterhorn Protocol 1.1	Checkpoint 31 (Fonts), index 31-012
PDF/UA-1 (ISO 14289-1)	Clause 7.21.4.2-1
WCAG 2.1	1.3.1 Info and Relationships — Level A
EN 301 549 / Section 508 / ADA Title II	All three point at WCAG 2.1 Level AA for non-web documents, so a Level A or AA criterion here is in scope for each of them.

Other conditions in checkpoint 31

Checkpoint 31 covers fonts. These are its other failure conditions; the ones without a link are in the rule set but do not have a written page yet.

Check your own file. Taggart does not check this condition yet, and lists it for you to confirm. Its validator is free and checks 75 of the 87 Matterhorn conditions software can decide — no watermark, no expiry, and no account needed up to 60 pages.

Check a PDF free

Taggart does not check this condition yet. A generated file that fails it is in the repository, with a test that fails the day Taggart starts catching it. Written on 2026-10-02. The Acrobat steps follow Adobe’s documentation and were not walked through by hand. Last updated 2026-10-02.