What causes "URL is required" in glanceapp/glance?

Set url: to the extension fragment's address, e.g. url: https://example.com/extension.html

URL is required

Error message

URL is required

What it means

Thrown by the extension widget's initialize() when no url field is set. Extensions are remote page fragments loaded from a URL (with a default 30-minute cache), so the URL is the only mandatory field; an unset one is rejected immediately.

Source

Thrown at internal/glance/widget-extension.go:35

const extensionWidgetDefaultTitle = "Extension"

type extensionWidget struct {
	widgetBase          `yaml:",inline"`
	URL                 string               `yaml:"url"`
	FallbackContentType string               `yaml:"fallback-content-type"`
	Parameters          queryParametersField `yaml:"parameters"`
	Headers             map[string]string    `yaml:"headers"`
	AllowHtml           bool                 `yaml:"allow-potentially-dangerous-html"`
	Extension           extension            `yaml:"-"`
	cachedHTML          template.HTML        `yaml:"-"`
}

func (widget *extensionWidget) initialize() error {
	widget.withTitle(extensionWidgetDefaultTitle).withCacheDuration(time.Minute * 30)

	if widget.URL == "" {
		return errors.New("URL is required")
	}

	if _, err := url.Parse(widget.URL); err != nil {
		return fmt.Errorf("parsing URL: %v", err)
	}

	return nil
}

func (widget *extensionWidget) update(ctx context.Context) {
	extension, err := fetchExtension(extensionRequestOptions{
		URL:                 widget.URL,
		FallbackContentType: widget.FallbackContentType,
		Parameters:          widget.Parameters,
		Headers:             widget.Headers,
		AllowHtml:           widget.AllowHtml,
	})

View on GitHub (pinned to 91324e8de7)

Solutions

Set url: to the extension fragment's address, e.g. url: https://example.com/extension.html
Verify the key is exactly 'url' and at the widget's top level
To actually disable an extension widget, remove or comment out the whole widget block instead of just the url

Example fix

# before
- type: extension
  # url: https://example.com/fragment.html
  parameters:
    key: value

# after
- type: extension
  url: https://example.com/fragment.html
  parameters:
    key: value

Defensive patterns

Strategy: validation

Validate before calling

if w['type'] == 'extension' and not w.get('url'):
    raise ValueError('extension widget requires url')

Prevention

Write the url first when adding an extension widget
Disable extensions by removing the whole block, not by deleting one key
Lint for required keys per widget type in CI

When it happens

Trigger: A widget of type: extension with only fallback-content-type, parameters, or headers configured; url misspelled (uri:, link:) or commented out; url present only in a copy of the widget that was renamed.

Common situations: Prototyping an extension entry and commenting the url out to 'disable' it; indentation placing url under parameters.

Related errors

AI-assisted analysis of glanceapp/glance@91324e8de7 (2026-08-15). Data as JSON: /api/errors/0dd2dce949ed8546. Report an issue: GitHub.