XTLS/Xray-core · error

"minClientVer[", i, "]" should be less than 256

Error message

"minClientVer[", i, "]" should be less than 256

What it means

Thrown by the REALITY builder when a component of minClientVer fails ParseUint with bitSize 8 — i.e. the number is negative or >= 256. Each version component must fit in one byte because the parsed result is stored into a [3]byte.

Source

Thrown at infra/conf/transport_security.go:111

		}
		if len(c.ServerNames) == 0 {
			return nil, errors.New(`empty "serverNames"`)
		}
		if c.PrivateKey == "" {
			return nil, errors.New(`empty "privateKey"`)
		}
		if config.PrivateKey, err = base64.RawURLEncoding.DecodeString(c.PrivateKey); err != nil || len(config.PrivateKey) != 32 {
			return nil, errors.New(`invalid "privateKey": `, c.PrivateKey)
		}
		if c.MinClientVer != "" {
			config.MinClientVer = make([]byte, 3)
			var u uint64
			for i, s := range strings.Split(c.MinClientVer, ".") {
				if i == 3 {
					return nil, errors.New(`invalid "minClientVer": `, c.MinClientVer)
				}
				if u, err = strconv.ParseUint(s, 10, 8); err != nil {
					return nil, errors.New(`"minClientVer[`, i, `]" should be less than 256`)
				} else {
					config.MinClientVer[i] = byte(u)
				}
			}
			errors.LogWarning(context.Background(), `REALITY: Changing "minClientVer" will increase the likelihood of your server's IP being blocked by the GFW`)
		} else {
			config.MinClientVer = []byte{26, 3, 27} // change it at your own risk: https://github.com/XTLS/Xray-core/commit/af7eb68028732a8ee3c0e5d6ab2b8a657bb2e770
			errors.LogWarning(context.Background(), `REALITY: The default minimal client version is Xray-core v26.3.27, other clients may be refused to connect`)
		}
		if c.MaxClientVer != "" {
			config.MaxClientVer = make([]byte, 3)
			var u uint64
			for i, s := range strings.Split(c.MaxClientVer, ".") {
				if i == 3 {
					return nil, errors.New(`invalid "maxClientVer": `, c.MaxClientVer)
				}
				if u, err = strconv.ParseUint(s, 10, 8); err != nil {
					return nil, errors.New(`"maxClientVer[`, i, `]" should be less than 256`)

View on GitHub (pinned to 7d214f8b09)

Solutions

1. Keep every component in 0-255 and numeric, e.g. "1.8.6".
2. Omit the field to use the safe default.

Example fix

// before
"minClientVer": "1.512.0"
// after
"minClientVer": "1.8.6"

func validVerComponent(s string) bool {
    _, err := strconv.ParseUint(s, 10, 8)
    return err == nil
}

When it happens

Trigger: Setting "minClientVer": "1.300.0" or "1.-2.3" (non-numeric strings also land here since ParseUint fails).

Common situations: Typos, or treating the field as a date/build number like "24.1234.5".

Related errors

• invalid "minClientVer":
• invalid "maxClientVer":
• "maxClientVer[", i, "]" should be less than 256
• REALITY: Empty "realitySettings".
• please fill in a valid value for "target"

AI-assisted analysis of XTLS/Xray-core@7d214f8b09 (2026-08-15). Data as JSON: /api/errors/a80de2a770e43528. Report an issue: GitHub.