gohugoio/hugo · error

failed to resolve output formats %v: %w

Error message

failed to resolve output formats %v: %w

What it means

During PageConfigLate.Compile, the page's `outputs` list from front matter (or a content adapter) is resolved against the site's configured output formats by name. If any name doesn't match a defined output format, GetByNames fails and Hugo aborts with this error, listing the requested names, because it cannot render the page to an unknown format.

Source

Thrown at resources/page/pagemeta/page_frontmatter.go:457

// Compile sets up the page configuration after all fields have been set.
func (p *PageConfigLate) Compile(e *PageConfigEarly, logger loggers.Logger, outputFormats output.Formats) error {
	if e.IsFromContentAdapter {
		if err := mapstructure.WeakDecode(p.ContentAdapterData, p); err != nil {
			err = fmt.Errorf("failed to decode page map: %w", err)
			return err
		}
	}

	if p.Params == nil {
		p.Params = make(hmaps.Params)
	} else {
		hmaps.PrepareParams(p.Params)
	}

	if len(p.Outputs) > 0 {
		outFormats, err := outputFormats.GetByNames(p.Outputs...)
		if err != nil {
			return fmt.Errorf("failed to resolve output formats %v: %w", p.Outputs, err)
		} else {
			p.ConfiguredOutputFormats = outFormats
		}
	}

	return nil
}

// MarkupToMediaType converts a markup string to a media type.
func MarkupToMediaType(s string, mediaTypes media.Types) media.Type {
	s = strings.ToLower(s)
	mt, _ := mediaTypes.GetBestMatch(markup.ResolveMarkup(s))
	return mt
}

type ResourceConfig struct {
	Path    string
	Name    string

View on GitHub ↗ (pinned to 8a468df065)

Solutions

1. Define the missing format in site config: [outputFormats.SearchIndex] mediaType = "application/json", baseName = "searchindex".
2. Fix the spelling in the page's outputs list to match a built-in or configured format name (names are matched case-insensitively but must exist).
3. Remove stale format names from front matter after deleting a custom output format from config.

Example fix

# before (front matter)
outputs: ["html", "searchindex"]
# after: add to hugo.toml
[outputFormats.searchindex]
mediaType = "application/json"
baseName = "searchindex"

# front matter outputs must name formats defined in config
---
outputs: ["html", "json"]
---
# config: ensure [outputFormats.json] exists (json is built-in)

When it happens

Trigger: Front matter like `outputs: ["html", "amp", "searchindex"]` where a name (e.g. "searchindex") isn't defined under [outputFormats] in site config; content adapters setting outputs with typos or lowercase/spelling variations of custom format names.

Common situations: Copying theme docs that assume a custom output format (JSON search index, RSS variants) without adding its [outputFormats.NAME] definition; typos like "jsonl" vs "json"; removing a custom output format from config while pages still reference it.

Related errors

• media type %q not found
• invalid output format configuration; wrong type for media ty
• failed to decode output format configuration: %w
• error processing file %q
• failed to parse file %q: %s

AI-assisted analysis of gohugoio/hugo@8a468df065 (2026-07-31). Data as JSON: /data/errors/0ec8673973faced3.json. Report an issue: GitHub ↗.