Validate email format

Here is a regular expression that validates a common email format:

^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$

Let me break it down:

• ^ matches the start of the string
• [a-zA-Z0-9._%+-]+ matches one or more of the following characters:
  • Letters (both uppercase and lowercase)
  • Numbers
  • Dot (.)
  • Hyphen (-)
  • Underscore (_)
  • Percent (%)
  • Plus sign (+)
• @ matches the @ symbol
• [a-zA-Z0-9.-]+ matches one or more of the following characters:
  • Letters (both uppercase and lowercase)
  • Numbers
  • Dot (.)
  • Hyphen (-)
• \. matches a period (.) character
• [a-zA-Z]{2,} matches the domain extension (it must be at least 2 characters long and only contain letters)
• $ matches the end of the string

This regular expression matches most common email formats, but keep in mind that it's not foolproof. Some email addresses may not match this pattern, and some valid email addresses may not match it either.

Here are some examples of valid email addresses that match this pattern:

• [email protected]
• [email protected]
• [email protected]
• [email protected]

And here are some examples of invalid email addresses that do not match this pattern:

• @example.com (missing local part)
• example..com (multiple dots in a row)
• [email protected] (missing domain)
• [email protected] (IP address instead of domain)

You can use this regular expression in your programming language of choice to validate email addresses. For example, in JavaScript:

const emailRegex = /^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$/;
const email = "[email protected]";
if (emailRegex.test(email)) {
  console.log("Valid email address");
} else {
  console.log("Invalid email address");
}

Note that this is just one possible way to validate email addresses, and there are many other approaches and regular expressions you can use depending on your specific requirements.