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GitHub Pages Jekyll build failed with an unknown tag error

Unknown tag error

GitHub Pages could not build the Jekyll site because Liquid or Jekyll encountered a tag that is unsupported, misspelled, or not available in the Pages build environment.

Unknown tag errorbuild errors

Observed message

Unknown tag error

Why it happens

  • The site uses an unsupported or misspelled Liquid or Jekyll tag.
  • The build depends on a plugin feature that GitHub Pages does not support.
  • Custom syntax was added that the Pages Jekyll environment cannot interpret.

How to fix it

  1. Check the reported tag name and correct any spelling or syntax mistakes.
  2. Replace unsupported tags with GitHub Pages-compatible alternatives.
  3. Remove or rework plugin-dependent tag usage if the Pages build environment does not support it.

Official reference

GitHub Docs: Troubleshooting Jekyll build errors for GitHub Pages sites

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GitHub Pages unknown tag error: causes and fixes | Error Atlas