invalid regexp name (must contain only word characters): %s

Error message

invalid regexp name (must contain only word characters): %s

What it means

Error "invalid regexp name (must contain only word characters): %s" thrown in caddyserver/caddy.

Source

Thrown at modules/caddytls/matchers.go:190

	compiled *regexp.Regexp
}

// Provision compiles the regular expression which may include placeholders.
func (mre *MatchRegexp) Provision(caddy.Context) error {
	repl := caddy.NewReplacer()
	re, err := regexp.Compile(repl.ReplaceAll(mre.Pattern, ""))
	if err != nil {
		return fmt.Errorf("compiling matcher regexp %s: %v", mre.Pattern, err)
	}
	mre.compiled = re
	return nil
}

// Validate ensures mre is set up correctly.
func (mre *MatchRegexp) Validate() error {
	if mre.Name != "" && !wordRE.MatchString(mre.Name) {
		return fmt.Errorf("invalid regexp name (must contain only word characters): %s", mre.Name)
	}
	return nil
}

// Match returns true if input matches the compiled regular
// expression in m. It sets values on the replacer repl
// associated with capture groups, using the given scope
// (namespace).
func (mre *MatchRegexp) Match(input string, repl *caddy.Replacer) bool {
	matches := mre.compiled.FindStringSubmatch(input)
	if matches == nil {
		return false
	}

	// save all capture groups, first by index
	for i, match := range matches {
		keySuffix := "." + strconv.Itoa(i)
		if mre.Name != "" {

View on GitHub (pinned to 50e54ee279)

Solutions

Use only word characters (letters, digits, underscore) in the regexp capture group name.

When it happens

Trigger: Thrown at modules/caddytls/matchers.go:190 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of caddyserver/caddy@50e54ee279 (2026-08-15). Data as JSON: /api/errors/9f4ce7868389f170. Report an issue: GitHub.