valyala/fasthttp · info

fasthttp: no cookies found

Error message

fasthttp: no cookies found

What it means

ErrNoCookies is returned by Response/Header & Cookie parsing helpers when scanning a Cookie header finds no valid cookies at all. The library distinguishes 'nothing to parse' from 'malformed value'. It signals an empty or entirely invalid cookie list.

Solutions

1. Check whether the Cookie header exists before parsing cookies
2. Treat ErrNoCookies as 'no session yet' and proceed to login/set-cookie flow
3. Guard iteration with a len check on the raw header value

Example fix

// before
cookies := resp.Header.Cookies() // may return ErrNoCookies
// after
if len(resp.Header.Peek("Cookie")) == 0 {
    return nil // no cookies yet, skip parsing
}
cookies := resp.Header.Cookies()

if len(resp.Header.Peek("Cookie")) == 0 {
    return nil // nothing to parse
}

func hasCookies(h *fasthttp.ResponseHeader) bool {
    return len(h.Peek("Cookie")) > 0
}

if err := parseCookies(h); errors.Is(err, fasthttp.ErrNoCookies) {
    return cookieSet{} // empty set is fine
}

When it happens

Trigger: Calling Response.Header.Cookies() / Response.Header.peek of Cookie header when the request/response carries no Cookie header or only whitespace; iterating cookies over an empty header.

Common situations: First request of a session with no cookies set yet; proxies stripping Cookie headers; code assuming cookies always exist after a redirect.

Related errors

• fasthttp: invalid cookie value
• cannot parse content-length
• fasthttp: need more data: cannot find trailing lf
• bufio read returned ( , nil)
• byte range is invalid for empty content

AI-assisted analysis of valyala/fasthttp@c96f600972 (2026-08-31). Data as JSON: /api/errors/044feda6478f75e8. Report an issue: GitHub.

Appendix: source

Thrown at cookie.go:379

	c.bufK = c.AppendBytes(c.bufK[:0])
	return c.bufK
}

// String returns cookie representation.
func (c *Cookie) String() string {
	return string(c.Cookie())
}

// WriteTo writes cookie representation to w.
//
// WriteTo implements io.WriterTo interface.
func (c *Cookie) WriteTo(w io.Writer) (int64, error) {
	n, err := w.Write(c.Cookie())
	return int64(n), err
}

var (
	ErrNoCookies          = errors.New("fasthttp: no cookies found")
	ErrInvalidCookieValue = errors.New("fasthttp: invalid cookie value")
)

// Parse parses Set-Cookie header.
func (c *Cookie) Parse(src string) error {
	c.bufK = append(c.bufK[:0], src...)
	return c.ParseBytes(c.bufK)
}

// ParseBytes parses Set-Cookie header.
func (c *Cookie) ParseBytes(src []byte) error {
	c.Reset()

	var s cookieScanner
	s.b = src

	var k, v []byte
	if !s.nextRaw(&k, &v) {

View on GitHub (pinned to c96f600972)