What makes email validation hard to get right?

The RFC 5322 email specification allows unusual but valid patterns like quoted local parts, plus addressing, and internationalized domain names. Simple regex validators reject valid addresses or accept invalid ones.

What is a valid semantic version string?

A valid semver string follows the format MAJOR.MINOR.PATCH, optionally followed by a pre-release identifier (e.g., 1.0.0-beta.1) and build metadata (e.g., 1.0.0+build.123).

How do I validate an IP address range?

The IP address validator checks both format validity (four octets, 0-255 each) and optionally whether the address falls within a specified CIDR range.

Validate Common Input Formats Online

Validating user input is a foundational task in web development, but implementing correct validators for email addresses, domain names, IP addresses, and semantic version strings requires knowing the relevant RFCs and edge cases. devtoolkit.sh provides instant validators for the most common input formats, each checking against the full specification rather than a simplified regex. Validate email addresses against RFC 5322, check domain name syntax, confirm IP addresses are valid and in range, and verify semantic version strings follow the semver specification. Use these tools during development to test your validation logic, in QA to check edge cases, and when auditing imported data for format compliance.

@Email Address Validator

Validate email addresses against RFC 5322 rules with local part, domain, and TLD breakdown.

🔗Domain Name Validator

Validate domain names against RFC 1035 rules: length, characters, labels, and TLD.

✓IP Address Validator

Validate IPv4 and IPv6 addresses with class, scope, and private/public detection.

vSemVer Validator

Validate semantic version strings and parse major, minor, patch, pre-release, and build metadata.

FAQ

What makes email validation hard to get right?: The RFC 5322 email specification allows unusual but valid patterns like quoted local parts, plus addressing, and internationalized domain names. Simple regex validators reject valid addresses or accept invalid ones.
What is a valid semantic version string?: A valid semver string follows the format MAJOR.MINOR.PATCH, optionally followed by a pre-release identifier (e.g., 1.0.0-beta.1) and build metadata (e.g., 1.0.0+build.123).
How do I validate an IP address range?: The IP address validator checks both format validity (four octets, 0-255 each) and optionally whether the address falls within a specified CIDR range.