Email Format Quick Check Per Cell

Check each cell against the WHATWG HTML single-email ASCII syntax after trimming boundaries; this checks format rather than mailbox existence or all RFC email forms.

Description

A plausible email address has a syntactic local part and domain, but syntax alone does not establish that a mailbox exists.

A plausible email address has a syntactic local part and domain, but syntax alone does not establish that a mailbox exists. This check uses the ASCII pattern associated with HTML's single-email input convention.^{[1, 2]}

Check each cell against the WHATWG HTML single-email ASCII syntax after trimming boundaries; this checks format rather than mailbox existence or all RFC email forms.

When to use Email Format Quick Check Per Cell

Use this tool to check each cell against the WHATWG HTML single-email ASCII syntax after trimming boundaries; this checks format rather than mailbox existence or all RFC email forms.

Choose the original CSV text, decoded cell strings, byte values or counts requested by this tool. Use the stated delimiter, encoding, indexing and number/date convention.

How to use Email Format Quick Check Per Cell and understand its results

Choose the original CSV text, decoded cell strings, byte values or counts requested by this tool. Use the stated delimiter, encoding, indexing and number/date convention.
Enter values using the field table and calculation rules, then run the tool.
Read valid. The explanation below defines the units, signs, ordering and any flags or placeholder values.
If the tool reports an input issue, correct the values and run it again. Apply the stated assumptions when interpreting a successfully returned result.

Input field	Meaning	Value type; see rules below	Requirement
values	Values	list of string; maximum length: 10000; minimum entries: 0; maximum entries: 10000	Required

Supply candidate cell strings. Each is trimmed at its boundaries and checked independently; the output is an aligned list of booleans. The local part permits ASCII letters, digits and the pattern's punctuation. Domain labels must begin and end with a letter or digit, allow internal hyphens and contain at most 63 characters. A dot in the domain is not required, and an empty cell evaluates false.

valid[i] = HTML-style single-email pattern matches trim(values[i])

Units, indexing, boundary conditions and exceptional cases are defined in the calculation rules above.

Output field	Meaning	Value type
valid	Valid	list of boolean

json

{
  "input": {
    "values": [
      "ada@example.org",
      "not-an-email",
      "a@localhost"
    ]
  },
  "output": {
    "valid": [
      true,
      false,
      true
    ]
  }
}

Limitations and assumptions

It does not check DNS, delivery, mailbox ownership or all RFC email forms. Quoted local parts, address lists and internationalized non-ASCII forms are outside the pattern; some unusual dot arrangements in the local part pass this lightweight test.

Numeric inputs must be finite. Follow the calculation-specific rules for overflow, underflow and exceptional cases. Cell-string lists also have a combined text budget of 100,000 UTF-16 units per list. Missing required fields, extra fields, wrong value types and violations of the calculation rules are input errors.

Alternative or Complementary methods

Use Column Type Inference From Sample: Infer empty, integer, decimal, or string from a column sample using ASCII decimal token syntax; blanks are ignored and leading-zero identifiers remain strings. For a complementary task, use ID Column Uniqueness Check: Check exact string ID uniqueness in a supplied column, treating empty strings and leading zeros literally; report indices of occurrences after each first occurrence.

Further background: HTML Standard: single-email input syntax.

References

Email Format Quick Check Per Cell — tool.io
HTML Standard: single-email input syntax — WHATWG

Similar or alternative tools

Column Type Inference From Sample
Infer empty, integer, decimal, or string from a column sample using ASCII decimal token syntax; blanks are ignored and leading-zero identifiers remain strings.
ID Column Uniqueness Check
Check exact string ID uniqueness in a supplied column, treating empty strings and leading zeros literally; report indices of occurrences after each first occurrence.