gofiber/fiber · error

protocol not supported; only http or https are allowed

Error message

protocol not supported; only http or https are allowed

What it means

Exported sentinel (client/core.go:302) signaling that a URL's scheme is neither http nor https. The client only speaks those two schemes (the same protocolCheck regex used in parserRequestURL), so any other scheme (ftp://, ws://, file://) is rejected. The error is exported for callers that want to perform the same validation before constructing a request.

Solutions

1. Reject or rewrite URLs whose scheme is not http/https before calling the client.
2. Use url.Parse and check u.Scheme ∈ {http, https}; compare against ErrNotSupportSchema if you mirror the library's check.
3. For WebSocket use the dedicated websocket middleware, not the HTTP client.
4. Document that only http and https are supported in your configuration surface.

Example fix

// before
u := "ftp://files.example.com/data"
req := client.Get().SetURL(u) // unsupported scheme

// after
u := "https://files.example.com/data"
req := client.Get().SetURL(u)

func validateScheme(rawURL string) error {
    u, err := url.Parse(rawURL)
    if err != nil { return err }
    if u.Scheme != "http" && u.Scheme != "https" {
        return fiber.ErrNotSupportSchema
    }
    return nil
}

if err := validateScheme(u); err != nil {
    if errors.Is(err, fiber.ErrNotSupportSchema) { /* reject input */ }
}

When it happens

Trigger: Passing a URL with a non-http(s) scheme to Request.SetURL; or validating a URL independently and comparing against this sentinel. (Note: the built-in hooks.go path currently surfaces ErrURLFormat for missing-scheme and fasthttp.ErrorInvalidURI for an unknown scheme during redirect; ErrNotSupportSchema is the public, stable sentinel for the same intent.)

Common situations: User-supplied URLs that include ws:// or ftp://; configuration loaders that accept arbitrary schemes; redirect chains that hop to a non-http scheme.

Related errors

• the URL is incorrect
• client: HTTPS to HTTP redirect blocked
• only file paths and io.Writer are supported
• the body type should be []byte
• the file should have a name

AI-assisted analysis of gofiber/fiber@a105acad6c (2026-08-11). Data as JSON: /api/errors/a665e854b325880a. Report an issue: GitHub.

Appendix: source

Thrown at client/core.go:302

// releaseErrChan returns the error channel to the pool.
// It's caller's responsibility to ensure that:
// - the channel is not closed
// - the channel is drained before returning it
// - the channel is not reused after returning it
func releaseErrChan(ch chan error) {
	errChanPool.Put(ch)
}

// newCore returns a new core object.
func newCore() *core {
	return &core{}
}

var (
	ErrTimeoutOrCancel      = errors.New("timeout or cancel")
	ErrURLFormat            = errors.New("the URL is incorrect")
	ErrNotSupportSchema     = errors.New("protocol not supported; only http or https are allowed")
	ErrFileNoName           = errors.New("the file should have a name")
	ErrBodyType             = errors.New("the body type should be []byte")
	ErrNotSupportSaveMethod = errors.New("only file paths and io.Writer are supported")
	ErrBodyTypeNotSupported = errors.New("the body type is not supported")
)

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