Before an address goes into a firewall rule, a DNS record, an allowlist, or a blocklist, it is worth confirming that it is actually an address at all. A single mistyped digit can silently break a rule or block the wrong range, and the failure often looks like a network problem rather than a typing problem. This validator checks syntax only: it confirms that an IPv4 address has four decimal octets in range, or that an IPv6 address follows the grouping and double-colon rules, and it tells you which version you have. It does not check whether the address is reachable, assigned, or in use, because syntax and reachability are different questions.
Quick Answer: Paste an address and click Validate: the tool reports Valid IPv4, Valid IPv6, or Invalid, with the reason.
Free Online Tool
IP Address Validator
Check whether an input is a syntactically valid IPv4 or IPv6 address, and which version.
How to Use the IP Address Validator
- Paste or type the address you want to check.
- Click Validate.
- Read the verdict: valid IPv4, valid IPv6, or invalid.
- If invalid, read the reason shown and fix that part of the input.
- Re-validate after each correction until the verdict is valid.
- Copy the validated address into your rule or record.
Key Features
- Separate IPv4 and IPv6 syntax checks with clear verdicts.
- Specific failure reasons instead of a bare invalid message.
- Rejects octets above 255 and groups above four hex digits.
- Rejects a second double colon and empty groups outside it.
- Works offline in your browser; nothing is sent anywhere.
- Accepts uppercase and lowercase IPv6 hex equally.
What the Result Means
A valid verdict means the string is well-formed, not that the address is live or belongs to you. An invalid verdict names the first problem found, so fix that and re-check; there may be a second problem behind it. Note that leading zeros in IPv4 octets, such as 010, are treated as decimal here, because some systems read them as octal and that ambiguity has caused real misconfigurations. When in doubt, write IPv4 octets without leading zeros.
Worked Example
Consider 192.168.1.256. The first three octets are fine, but the fourth exceeds 255, so the tool reports invalid and names the fourth octet as the problem. Fixing it to 192.168.1.25 gives a valid IPv4 verdict. Now consider 2001:db8::1::1, which contains the double colon twice. The tool rejects it immediately, because a second double colon makes the group count ambiguous. Removing the second group gives 2001:db8::1, which validates as IPv6.
Best Practices and Tips
- Validate addresses copied from tickets and spreadsheets before pasting them into firewall rules.
- Validate both endpoints of a tunnel or peering session, not just your own side.
- If an address fails here but works elsewhere, check for invisible characters such as a trailing space.
- Use this check before adding an address to an allowlist so a typo cannot lock out legitimate traffic.
- Remember that a valid private address is still valid syntax; classification is a separate step.
Common Mistakes to Avoid
- Assuming a valid address must be reachable; syntax says nothing about routing.
- Writing IPv4 octets larger than 255, such as 192.168.1.300.
- Using two double colons in an IPv6 address.
- Confusing validation with classification: a valid address can still be private, reserved, or bogus.
Frequently Asked Questions
Does this check if the IP is online?
No. It checks syntax only. Reachability needs a ping or a connection attempt, which a browser page cannot honestly perform for arbitrary hosts.
Is 192.168.001.001 valid?
This tool accepts it as decimal but warns by treating leading zeros as decimal digits. Many systems interpret leading zeros as octal, so avoid them in real configs.
Why is ::1 valid?
It is the IPv6 loopback address: the double colon stands for seven groups of zeros, leaving the final group as 1.
Can an address be both IPv4 and IPv6?
No. The two syntaxes are disjoint, and the tool reports exactly one version for a valid input.