gohugoio/hugo · error

failed to split baseURL hostport: %w

Error message

failed to split baseURL hostport: %w

What it means

While rewriting the baseURL for serving with `--appendPort` enabled, Hugo strips any existing port from the URL's host before appending the live server port. If the host contains a `:` but `net.SplitHostPort` cannot split it, the baseURL host is malformed and server startup fails with this wrapped error.

Source

Thrown at commands/server.go:838

		if err != nil {
			return "", err
		}
	}

	if useLocalhost {
		if certsSet {
			u.Scheme = "https"
		} else if u.Scheme == "https" {
			u.Scheme = "http"
		}
		u.Host = "localhost"
	}

	if c.serverAppend {
		if strings.Contains(u.Host, ":") {
			u.Host, _, err = net.SplitHostPort(u.Host)
			if err != nil {
				return "", fmt.Errorf("failed to split baseURL hostport: %w", err)
			}
		}
		u.Host += fmt.Sprintf(":%d", port)
	}

	return u.String(), nil
}

func (c *serverCommand) partialReRender(urls ...string) (err error) {
	defer func() {
		c.errState.setWasErr(false)
	}()
	visited := types.NewEvictingQueue[string](len(urls))
	for _, url := range urls {
		visited.Add(url)
	}

	var h *hugolib.HugoSites

View on GitHub ↗ (pinned to 8a468df065)

Solutions

1. Fix the host portion of `baseURL`: IPv6 literals must be bracketed, e.g. `http://[::1]:1313/`.
2. Remove stray or duplicated colons from the configured baseURL or `--baseURL` flag value.
3. Since Hugo appends the port itself when `--appendPort` is on (the default), you can omit the port from baseURL entirely.

Example fix

# before (hugo.toml)
baseURL = "http://::1/"
# after
baseURL = "http://[::1]/"

if _, _, err := net.SplitHostPort(u.Host); err != nil {
    // no port present — acceptable, but make sure host isn't malformed (e.g. bad IPv6 brackets)
    if strings.Contains(u.Host, ":") {
        return fmt.Errorf("malformed host:port in baseURL %q: %w", baseURL, err)
    }
}

When it happens

Trigger: `fixURL` on a baseURL whose parsed `u.Host` contains `:` yet fails `net.SplitHostPort` — e.g. an unbracketed IPv6 address (`baseURL = "http://::1/"`), multiple colons, or a garbage host like `example.com:80:90`.

Common situations: Using IPv6 literals in `baseURL` or `-b` without square brackets (`[::1]:1313`); typos leaving a trailing/double colon in the host (`example.com::1313`); templated baseURLs in CI concatenating host and port incorrectly.

Related errors

• failed to create baseURL from %q: %s
• cannot use --renderToMemory with --destination
• failed to parse root certificate
• failed to parse certificate PEM
• failed to parse certificate: %v

AI-assisted analysis of gohugoio/hugo@8a468df065 (2026-07-31). Data as JSON: /data/errors/20ed961a6eae6a11.json. Report an issue: GitHub ↗.