Jekyll "Conversion error: kramdown" in CI

By Kaveh Alemi·Latchkey

Jekyll uses kramdown to convert Markdown to HTML, and the conversion of a specific file raised. The cause is commonly a syntax-highlighter mismatch (Rouge vs configured highlighter) or a kramdown extension issue.

What this error means

jekyll build fails with "Conversion error: Jekyll::Converters::Markdown encountered an error while converting 'FILE'" and an underlying kramdown or highlighter message.

Conversion error: Jekyll::Converters::Markdown encountered an error while converting
'_posts/2026-06-01-intro.md':
                    Error: Highlighter 'pygments' is not supported

Common causes

An unsupported syntax highlighter

kramdown is configured to use a highlighter (for example pygments) that the build does not provide; modern Jekyll uses Rouge.

A kramdown parse or extension failure

A malformed table, math block, or extension input makes kramdown raise while converting that file.

How to fix it

Use the Rouge highlighter

1. Set kramdown to use Rouge in _config.yml.
2. Remove references to unsupported highlighters.
3. Rebuild.

# _config.yml
markdown: kramdown
kramdown:
  syntax_highlighter: rouge

Fix the offending Markdown

Re-run with --trace to find the line, then correct the malformed construct kramdown could not parse.

bundle exec jekyll build --trace

How to prevent it

• Configure kramdown with the Rouge highlighter.
• Validate tables and math blocks before committing.
• Use --trace to locate the converting file.

Frequently asked questions

Related guides

References

• Node.js documentation
• npm CLI documentation
• GitHub Actions documentation