Validate Email Addresses in YAML Files Online

Validate email addresses in YAML files directly in your browser. Add a boolean column flagging valid and invalid emails, or filter to show only invalid rows — no upload required.

How to validate Email Addresses in YAML files

Drop your file onto the upload area. It is loaded into the in-browser engine and the first 200 rows are shown.
Choose the email column. The tool preselects the first column whose name contains "email" or "mail", otherwise the first column.
Pick an action: Flag all rows adds an email_valid column (true or false), Keep invalid only returns the rows that fail, and Keep valid only returns the rows that pass.
Click Validate Emails. The counts of valid and invalid addresses and the percentage invalid appear next to the result.
Download the result in the same format you uploaded.

Your file is processed locally in your browser and is never uploaded. The free limit is 50 MB per file; larger files work if your device has the memory for them.

Worked example

A conference exports its registration sheet before sending joining instructions. Some addresses were typed by hand at the desk, and one attendee left the field empty.

Input (YAML)

- attendee: Priya Nair
  email: priya.nair@uni.edu
  ticket: student
- attendee: Jonas Weber
  email: jonas.weber@firma
  ticket: standard
- attendee: Sam O'Neill
  email: sam.o'neill@mail.ie
  ticket: standard
- attendee: Lucía Gómez
  email: lucia.gomez@correo.es
  ticket: speaker
- attendee: Wei Chen
  email: null
  ticket: student
- attendee: Tom Hart
  email: TOM.HART@Example.CO.UK
  ticket: standard

Settings

Email column: email
Action: Flag all rows

Result

attendee	email	ticket	email_valid
Priya Nair	priya.nair@uni.edu	student	true
Jonas Weber	jonas.weber@firma	standard	false
Sam O'Neill	sam.o'neill@mail.ie	standard	false
Lucía Gómez	lucia.gomez@correo.es	speaker	true
Wei Chen	NULL	student	NULL
Tom Hart	TOM.HART@Example.CO.UK	standard	true

Jonas's address has no dot and suffix after the domain, so it fails. Sam's address is legal under the email standard, but the apostrophe is outside the allowed character set, so it is flagged false. Upper case is fine. The empty cell gets no verdict. The summary reads 3 valid, 2 invalid (40.0% invalid), and Wei Chen is counted in neither.

Frequently Asked Questions

What rule does the validator apply?

The whole value must be a local part of letters, digits and . _ % + -, then one @, then a domain of letters, digits, dots and hyphens ending in a dot and at least two letters. It is a practical format check, not a full RFC 5322 parser.

Can valid addresses be rejected, or bad ones accepted?

Yes, at the edges. Legal but unusual addresses fail, such as ones with an apostrophe, accented letters, quoted local parts or punycode endings like .xn--p1ai. A few malformed ones pass, such as those with two dots in a row. Review the invalid list before deleting anything.

Does it check that the mailbox exists?

No. Nothing is sent and no domain lookups are made. The check runs in your browser against the text only. Use a verification service if you need deliverability checks.

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