WordPress/gutenberg

Custom font upload not working

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#72265 opened on Oct 11, 2025

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 (15 comments) (0 reactions) (1 assignee)JavaScript (9,607 stars) (3,893 forks)batch import
Good First Issue[Feature] Font Library[Status] In Progress[Type] Bug

Description

Description

When trying to install this font it wouldn't complete and instead we are seeing a browser console error.

Step-by-step reproduction instructions

  1. Go to Appearance > Editor
  2. Styles > Fonts
  3. Try uploading this font:

AaDaoShuRi-LangManHeiTi-2.ttf.zip

Screenshots, screen recording, code snippet

The console renders:

Uncaught (in promise) SyntaxError: Invalid font data in ArrayBuffer

Th workaround is to convert it to a .woff2. I've used https://transfonter.org/

Environment info

WordPress 6.9 and the current stable version

Please confirm that you have searched existing issues in the repo.

  • Yes

Please confirm that you have tested with all plugins deactivated except Gutenberg.

  • Yes

Please confirm which theme type you used for testing.

  • Block
  • Classic
  • Hybrid (e.g. classic with theme.json)
  • Not sure

Contributor guide

Tech stack
javascriptreact
Domain
frontend
Issue type
bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
blocked
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
mostly clear
Prerequisites
Understand basic font file formatsFamiliarity with JavaScript promises
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
30
Research direction
The issue occurs when uploading a .ttf font file; the console shows 'Invalid font data in ArrayBuffer'. The workaround is to convert to .woff2. Investigate how font files are validated in the editor, likely in the font upload component or API handler. Look at recent changes related to font asset loading. Check if the issue is specific to certain font types or to the parsing logic. Consider opening the linked file (AaDaoShuRi LangManHeiTi 2.ttf.zip) to reproduce the error.