Validate Email Addresses in Excel Files Online
Validate email addresses in Excel 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 Excel 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 (Excel)
Excel workbook, first sheet (Sheet1)
| attendee | ticket | |
|---|---|---|
| Priya Nair | priya.nair@uni.edu | student |
| Jonas Weber | jonas.weber@firma | standard |
| Sam O'Neill | sam.o'neill@mail.ie | standard |
| Lucía Gómez | lucia.gomez@correo.es | speaker |
| Wei Chen | NULL | student |
| Tom Hart | TOM.HART@Example.CO.UK | standard |
Settings
- Email column: email
- Action: Flag all rows
Result
| attendee | 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.
Working with Excel files
The first sheet is read as the text each cell shows, and that is what gets checked. That matters for hyperlinks. A cell that shows "Contact Jane" but links to mailto:jane@example.com is checked as "Contact Jane" and fails. Put the real addresses in the column as plain text before uploading. Line breaks inside a cell (Alt+Enter) also make an address fail. So do addresses pasted from Outlook as Jane Doe <jane@example.com>, because the name and angle brackets are part of the cell text.
In Flag mode, the downloaded Sheet1 holds email_valid as real TRUE and FALSE cells, so AutoFilter can pull out the failures. Keep invalid only is useful as a correction list. Hand it to whoever owns the data, fix the addresses, and run the tool again. Cell colours, comments and other sheets are not carried over to the output.
Frequently Asked Questions
Why do Excel cells with mailto links fail validation?
The tool checks the text the cell displays, not the link target. If the display text is a name rather than the address, it fails. Replace the display text with the address itself.
Can I sort by validity in Excel afterwards?
Yes. email_valid is written as TRUE and FALSE cells, so it sorts and filters like any Excel boolean column.
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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